false2023-09-30Q20001335730--03-31http://fasb.org/us-gaap/2023#InterestExpenseDepositshttp://fasb.org/us-gaap/2023#InvestmentIncomeInteresthttp://fasb.org/us-gaap/2023#AccruedInvestmentIncomeReceivablehttp://fasb.org/us-gaap/2023#AccruedInvestmentIncomeReceivableThe majority of total foreign consist of corporate. Gains (losses) in Earnings are reported in Other noninterest income (expenses). Gains (losses) in OCI are reported in Other comprehensive income (loss). Amounts represent total gains or losses recognized in earnings and other comprehensive income (loss) during the period. These gains or losses were attributable to the change in fair value relating to assets and liabilities classified as Level 3 that were still held at September 30, 2022 and 2023. The amounts of unrealized gains (losses) in other comprehensive income (loss) are related to Available-for-sale securities and Long-term debt, which were ¥5 billion and ¥6 billion, respectively, at September 30, 2022, and ¥12 billion and ¥(14) billion, respectively, at September 30, 2023.The primary component of the retail portfolio segment is housing loans to individuals which obligor category is classified based on past due status. The trigger to reclassify obligors from normal obligors to watch obligors excluding special attention obligors is when the past due status is more than 30 days.Proceeds from sales of Equity securities as well as Purchases of Equity securities include cash activity related to Other investments, the amounts of which are not significant. Derivative assets and liabilities are recorded in Trading account assets and Trading account liabilities, respectively.Amounts relating to master netting arrangements or similar agreements where the MHFG Group does not have the legal right of set-off or where uncertainty exists as to the enforceability of these agreements are excluded. For derivatives, the table includes amounts relating to over-the-counter (“OTC”) and OTC-cleared derivatives that are subject to enforceable master netting arrangements or similar agreements.For derivatives, amounts include derivative assets or liabilities and securities collateral that are eligible for offsetting under enforceable master netting arrangements or similar agreements.Amounts do not exceed the net amounts presented on the balance sheet and do not include the effect of overcollateralization, where it exists.The amounts of Receivables under securities borrowing transactions and Payables under securities lending transactions subject to enforceable industry standard master lending agreements with netting terms were ¥1,892 billion and ¥758 billion, respectively, at March 31, 2023, and ¥1,817 billion and ¥1,088 billion, respectively, at September 30, 2023.The amounts of Receivables under resale agreements and Payables under repurchase agreements subject to enforceable industry standard master repurchase agreements with netting terms were ¥10,587 billion and ¥25,147 billion, respectively, at March 31, 2023, and ¥14,433 billion and ¥31,872 billion, respectively, at September 30, 2023.The amounts of derivative assets and liabilities subject to enforceable master netting arrangements or similar agreements were ¥12,574 billion and ¥12,432 billion, respectively, at March 31, 2023, and ¥18,438 billion and ¥18,475 billion, respectively, at September 30, 2023.Gains (losses) in Earnings are reported in Trading account gains (losses)-net, Foreign exchange gains (losses)-net or Other noninterest income (expenses). Total Level 3 derivative exposures have been netted on the table for presentation purposes only. Gains (losses) in Earnings are reported in Investment gains (losses)-net. Investment grade in the internal rating scale generally corresponds to BBB- or above in the external rating scale.Derivative receivables and payables are recorded in Trading account assets and Trading account liabilities, respectively.Others for the six months ended September 30, 2022 includes primarily foreign exchange translation. Others for the six months ended September 30, 2023 includes an increase of approximately ¥25 billion related to foreign exchange translation and ¥22 billion related to loans held for sale. Charge-offs decreased from ¥163,612 million for the six months ended September 30, 2022 to ¥23,541 million for the six months ended September 30, 2023. The decrease was due mainly to a charge-off related to a debt waiver to a domestic corporate borrower which was recognized in the six months ended September 30, 2022. The required ratios disclosed above, at March 31, 2023 and September 30, 2023, include the capital conservation buffer of 2.5%, the countercyclical capital buffer of 0.06% and 0.1%, respectively, and the additional loss absorbency requirements for global systemically important banks (“G-SIBs”) and domestic systemically important banks (“D-SIBs”) of 1.0%, which are all in addition to the regulatory minima. The respective required amounts are determined by applying the ratios to the sum of the risk weighted assets and certain other risk amounts. Guaranteed trust principal, included in All other liabilities in the disclosure about consolidated VIEs in the accompanying balance sheets, is a liability of certain consolidated trust arrangements that meet the definition of a VIE for which the MHFG Group provides guarantees for the repayment of principal. See Note 15 “Variable interest entities and securitizations” for further discussion of the guaranteed principal money trusts. The MHFG Group included premises and equipment classified as held for sale in Other. Commitments to extend credit include commitments to invest in securities.Trading securities include foreign currency denominated securities for which the MHFG Group elected the fair value option. For the six months ended September 30, 2022, the performance-based plan under the stock compensation programs could potentially dilute earnings per common share but were not included in the computation of diluted earnings per common share due to their antidilutive effects. In addition, for the six months ended September 30, 2022, the computation of diluted earnings per common share did not assume exercise of stock options, as the effect of such exercise would be antidilutive due to net loss. These amounts are revenues from contracts within the scope of ASC 606, “Revenue from contracts with customers” (“ASC 606”). Part of these amounts are considered to be revenues from contracts that are within the scope of ASC 606. Most of the lending-related fees such as commitment fees and arrangement fees are not within the scope of ASC 606. This represents the maximum amount the Group could possibly be required to record in its consolidated statements of income associated with on-balance-sheet exposures and off-balance-sheet liabilities such as undrawn commitments. These amounts include the net unrealized gains resulting from changes in fair values of structured notes that contain embedded derivatives. See Note 17 “Fair value” for further details. These amounts are revenues from contracts that do not meet the scope of ASC 606. These inputs are mainly used for determining the fair values of securitization products such as CDO, CLO and ABS, other than RMBS and CMBS. Averages are calculated by weighting each input by the relative fair value of the respective financial instruments except for derivative related inputs where medians are used. Internal valuation model includes discounted cash flow models and the Black-Scholes option pricing model. All Agency mortgage-backed securities presented in this line are Ginnie Mae securities. Amortized cost, net of the allowance for credit losses, of which the amounts related to available-for-sale securities were ¥nil at both March 31, 2023 and September 30, 2023.Accrued interest receivables are excluded from amortized cost, of which the amount were ¥5,637 million at March 31, 2023, and ¥11,930 million at September 30, 2023 and included in Accrued income.Other debt securities presented in this line primarily consist of Foreign negotiable certificates of deposit (“NCDs”) and asset-backed securities (“ABS”), of which the total fair values were ¥330,365 million at March 31, 2023, and ¥231,937 million at September 30, 2023.Agency mortgage-backed securities presented in this line consist of Japanese and Foreign agency mortgage-backed securities, of which the fair values were ¥522,166 million and ¥31 million, respectively, at March 31, 2023, and ¥513,041 million and ¥27 million, respectively, at September 30, 2023. All Japanese agency mortgage-backed securities are issued by Japan Housing Finance Agency, a Japanese government-sponsored enterprise. Foreign agency mortgage-backed securities primarily consist of Government National Mortgage Association (“Ginnie Mae”) securities, which are guaranteed by the United States government.Agency mortgage-backed securities presented in this line consist of Japanese agency mortgage-backed securities, of which the fair values were ¥381,634 million at March 31, 2023, and ¥0 million at September 30, 2023. All Japanese agency mortgage-backed securities are issued by Japan Housing Finance Agency, a Japanese government-sponsored enterprise. Cash and cash equivalents consists of Cash and due from banks and Interest-bearing deposits in other banks. Cash deposited with central banks that must be maintained to meet minimum regulatory requirements is classified as restricted cash and included in Cash and cash equivalents. Notional amount includes the sum of gross long and gross short third-party contracts.The required and actual amounts disclosed above at March 31, 2023 and September 30, 2023 exclude amounts of deposits to the Bank of Japan.Amounts include the net gains (losses) of ¥172 million and ¥(365) million on the credit derivatives economically managing the credit risk of loans during the six months ended September 30, 2022 and 2023, respectively.The amounts that have been reclassified out of Accumulated other comprehensive income (loss), net of tax into net income are presented in Note 8 “Accumulated other comprehensive income (loss), net of tax.” “Fixed assets” is presented based on Japanese GAAP and corresponds to the total amount of the following U.S. GAAP accounts: Premises and equipment-net; Goodwill; Intangible assets; and right-of-use assets related to operating leases included in Other assets. The above table does not include other asset amounts because “Fixed assets” is the only balance sheet metric that management uses when evaluating and making decisions pertaining to the operating segments. “Others” in “Fixed assets” includes assets of headquarters that have not been allocated to each segment, “Fixed assets” pertaining to consolidated subsidiaries that are not subject to allocation, consolidating adjustments, and others. Certain “Fixed assets” expenses have been allocated to each segment using reasonable allocation criteria. Income and expenses of foreign branches of MHBK and foreign subsidiaries with functional currencies other than Japanese Yen have been translated for purposes of segment reporting using the budgeted foreign currency rates. Prior period comparative amounts for such foreign currency income and expenses have been translated using current period budgeted foreign currency rates. “Others” includes the following items: • profits and expenses pertaining to consolidated subsidiaries that are not subject to allocation; • consolidating adjustments, including elimination of internal transaction between each segment; • equity in earnings (losses) of equity method investees-net that are not subject to allocation; and • profits and losses pertaining to derivative transactions that reflect the counterparty risk of the individual parties and other factors in determining fair market value.Net business profits (losses) is used in Japan as a measure of the profitability of core banking operations, and is defined as gross profits (as defined above) less general and administrative expenses (excluding non-allocated gains (losses), net) plus equity in earnings (losses) of equity method investees-net less amortization of goodwill and others. Measurement of net business profits (losses) is required for regulatory reporting to the Financial Services Agency of Japan.“General and administrative expenses” excludes non-allocated gains (losses), net.“Gross profits + Net gains (losses) related to ETFs and others” is reported instead of sales reported by general corporations. Gross profits is defined as the sum of net interest income, fiduciary income, net fee and commission income, net trading income and net other operating income. Net gains (losses) related to ETFs and others consist of net gains (losses) on ETFs held by MHBK and MHTB on their non-consolidated basis and net gains (losses) on operating investment securities of MHSC on its consolidated basis. For the six months ended September 30, 2022 and 2023, net gains (losses) related to ETFs and others amounted to ¥8.7 billion and ¥180.0 billion, respectively, of which ¥7.6 billion and ¥0.3 billion are included in “GMC,” respectively.The required ratios disclosed above, at March 31, 2023 and September 30, 2023, include a leverage ratio buffer required to be met at 50% of the additional loss absorbency requirements applied to the Group as a G-SIB under the finalized Basel III reforms. The U.S. GAAP adjustments are primarily comprised of GAAP differences mainly from right-of-use assets related to operating leases not recognized under Japanese GAAP; internally developed software, which was impaired under Japanese GAAP; land, which was revalued under Japanese GAAP; and the consolidation of certain variable interest entities, which are not consolidated under Japanese GAAP.This input is mainly used for determining the fair values of Japanese corporate bonds and foreign corporate bonds. Loans, net of allowance include items measured at fair value on a nonrecurring basis.The amount includes CLO and convertible bonds, which are classified in Level 3. In accordance with ASC 820, certain investments that are measured at fair value using the net asset value per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented for these classes of assets are intended to permit the reconciliation of the fair value hierarchy to the amounts presented in the statements of financial position. The amounts of unfunded commitments related to these investments at March 31, 2023 and September 30, 2023 were ¥52 billion and ¥65 billion, respectively.Amounts represent items for which the Group elected the fair value option or for which it applied the practicability exception. 0001335730 2023-09-30 0001335730 2023-03-31 0001335730 2022-04-01 2022-09-30 0001335730 2023-04-01 2023-09-30 0001335730 2022-04-01 2023-03-31 0001335730 2022-09-30 0001335730 2022-03-31 0001335730 mfg:ClassSixteenPreferredStockMember 2023-03-31 0001335730 mfg:ClassFourteenPreferredStockMember 2023-03-31 0001335730 mfg:ClassFifteenPreferredStockMember 2023-03-31 0001335730 us-gaap:MaturityUpTo30DaysMember 2023-03-31 0001335730 us-gaap:MaturityOver90DaysMember 2023-03-31 0001335730 mfg:MaturityOvernightAndOpenMember 2023-03-31 0001335730 mfg:Maturity31To90DaysMember 2023-03-31 0001335730 us-gaap:MortgageBackedSecuritiesOtherMember mfg:DomesticGovernmentSponsoredEnterprisesDebtSecuritiesMember us-gaap:DebtSecuritiesMember 2023-03-31 0001335730 mfg:MizuhoFinancialGroupInc.Member 2023-03-31 0001335730 us-gaap:PerformanceGuaranteeMember 2023-03-31 0001335730 us-gaap:GuaranteeTypeOtherMember 2023-03-31 0001335730 us-gaap:PaymentGuaranteeMember 2023-03-31 0001335730 us-gaap:FinancialGuaranteeMember 2023-03-31 0001335730 mfg:GuaranteesForRepaymentOfTrustPrincipalMember 2023-03-31 0001335730 us-gaap:MarketValueGuaranteeMember 2023-03-31 0001335730 mfg:GuaranteesOnTrustAccountsMember 2023-03-31 0001335730 mfg:ExpirationPeriodAfterOneYearThroughFiveYearsMember 2023-03-31 0001335730 mfg:ExpirationPeriodAfterFiveYearsMember 2023-03-31 0001335730 mfg:ExpirationPeriodOneYearOrLessMember 2023-03-31 0001335730 mfg:DebtInstrumentMember 2023-03-31 0001335730 us-gaap:MortgageBackedSecuritiesOtherMember mfg:ForeignAgencyMortgageBackedSecuritiesMember us-gaap:DebtSecuritiesMember 2023-03-31 0001335730 mfg:NegotiableCertificatesOfDepositsAssetBackedSecuritiesAndCollateralLoanObligationsMember us-gaap:DebtSecuritiesMember 2023-03-31 0001335730 us-gaap:AvailableforsaleSecuritiesMember us-gaap:DebtSecuritiesMember us-gaap:MunicipalBondsMember 2023-03-31 0001335730 us-gaap:AvailableforsaleSecuritiesMember us-gaap:DebtSecuritiesMember us-gaap:MortgageBackedSecuritiesOtherMember 2023-03-31 0001335730 mfg:GovernmentBondsMember us-gaap:DebtSecuritiesMember us-gaap:AvailableforsaleSecuritiesMember 2023-03-31 0001335730 us-gaap:AvailableforsaleSecuritiesMember us-gaap:DebtSecuritiesMember 2023-03-31 0001335730 us-gaap:CommercialMortgageBackedSecuritiesMember us-gaap:DebtSecuritiesMember us-gaap:AvailableforsaleSecuritiesMember 2023-03-31 0001335730 mfg:ForeignGovernmentBondsMember us-gaap:DebtSecuritiesMember us-gaap:AvailableforsaleSecuritiesMember 2023-03-31 0001335730 us-gaap:AvailableforsaleSecuritiesMember us-gaap:DebtSecuritiesMember mfg:DomesticDebtSecuritiesMember 2023-03-31 0001335730 us-gaap:ResidentialMortgageBackedSecuritiesMember us-gaap:DebtSecuritiesMember us-gaap:AvailableforsaleSecuritiesMember 2023-03-31 0001335730 us-gaap:USTreasuryAndGovernmentShorttermDebtSecuritiesMember us-gaap:DebtSecuritiesMember us-gaap:AvailableforsaleSecuritiesMember 2023-03-31 0001335730 us-gaap:DebtSecuritiesMember us-gaap:ForeignCorporateDebtSecuritiesMember us-gaap:AvailableforsaleSecuritiesMember 2023-03-31 0001335730 us-gaap:USTreasuryAndGovernmentShorttermDebtSecuritiesMember us-gaap:DebtSecuritiesMember 2023-03-31 0001335730 us-gaap:DebtSecuritiesMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2023-03-31 0001335730 us-gaap:DebtSecuritiesMember us-gaap:ForeignCorporateDebtSecuritiesMember 2023-03-31 0001335730 mfg:GovernmentBondsMember us-gaap:DebtSecuritiesMember 2023-03-31 0001335730 mfg:DomesticDebtSecuritiesMember us-gaap:DebtSecuritiesMember 2023-03-31 0001335730 us-gaap:MunicipalBondsMember us-gaap:DebtSecuritiesMember 2023-03-31 0001335730 us-gaap:MortgageBackedSecuritiesOtherMember us-gaap:DebtSecuritiesMember 2023-03-31 0001335730 mfg:ForeignGovernmentBondsMember us-gaap:DebtSecuritiesMember 2023-03-31 0001335730 us-gaap:CommercialMortgageBackedSecuritiesMember us-gaap:DebtSecuritiesMember 2023-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 us-gaap:ResidentialMortgageBackedSecuritiesMember mfg:AvailableForSaleAndTradingSecuritiesMember 2023-03-31 0001335730 us-gaap:AllOtherCorporateBondsMember mfg:AvailableForSaleAndTradingSecuritiesMember 2023-03-31 0001335730 mfg:OtherContractsMember us-gaap:DerivativeMember 2023-03-31 0001335730 us-gaap:ForeignExchangeContractMember us-gaap:DerivativeMember 2023-03-31 0001335730 us-gaap:EquityContractMember us-gaap:DerivativeMember 2023-03-31 0001335730 us-gaap:CreditRiskContractMember us-gaap:DerivativeMember 2023-03-31 0001335730 us-gaap:InterestRateContractMember us-gaap:DerivativeMember 2023-03-31 0001335730 mfg:ImpairedFinancingReceivablesWithNoRelatedAllowanceMember 2023-03-31 0001335730 mfg:MarketableEquitySecuritiesMember 2023-03-31 0001335730 mfg:MizuhoFinancialGroupIncMember mfg:JapanGaapConsolidatedMember 2023-03-31 0001335730 mfg:JapanGaapUnconsolidatedAffiliatesMember mfg:MizuhoBankLimitedMember 2023-03-31 0001335730 mfg:MizuhoBankLimitedMember mfg:JapanGaapConsolidatedMember 2023-03-31 0001335730 mfg:JapanGaapUnconsolidatedAffiliatesMember mfg:MizuhoTrustBankingCompanyLimitedMember 2023-03-31 0001335730 mfg:JapanGaapConsolidatedMember mfg:MizuhoTrustBankingCompanyLimitedMember 2023-03-31 0001335730 mfg:CreditRiskContractWrittenMember us-gaap:ExternalCreditRatingInvestmentGradeMember 2023-03-31 0001335730 mfg:CreditRiskContractPurchasedMember 2023-03-31 0001335730 mfg:CreditRiskContractWrittenMember us-gaap:ExternalCreditRatingNonInvestmentGradeMember 2023-03-31 0001335730 mfg:CreditRiskContractWrittenMember 2023-03-31 0001335730 mfg:PerformanceFinancialMarketValueAndOtherTypeGuaranteeMember 2023-03-31 0001335730 us-gaap:RiskLevelLowMember mfg:PerformanceFinancialMarketValueAndOtherTypeGuaranteeMember 2023-03-31 0001335730 us-gaap:RiskLevelHighMember mfg:PerformanceFinancialMarketValueAndOtherTypeGuaranteeMember 2023-03-31 0001335730 us-gaap:CommitmentsToExtendCreditMember 2023-03-31 0001335730 us-gaap:UnusedLinesOfCreditMember 2023-03-31 0001335730 us-gaap:LongTermDebtMember 2023-03-31 0001335730 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsNonrecurringMember 2023-03-31 0001335730 us-gaap:FairValueMeasurementsNonrecurringMember 2023-03-31 0001335730 us-gaap:PortionAtOtherThanFairValueFairValueDisclosureMember us-gaap:FairValueMeasurementsNonrecurringMember 2023-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:HousingLoanMember 2023-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:SmallAndMediumSizedCompaniesMember 2023-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember 2023-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:OtherMember 2023-03-31 0001335730 mfg:LargeCompaniesMember mfg:CorporateRatingMember us-gaap:GeographicDistributionDomesticMember 2023-03-31 0001335730 us-gaap:GeographicDistributionForeignMember 2023-03-31 0001335730 us-gaap:FairValueMeasurementsNonrecurringMember us-gaap:FairValueInputsLevel2Member 2023-03-31 0001335730 srt:MaximumMember us-gaap:MeasurementInputDiscountRateMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:ResidentialMortgageBackedSecuritiesMember mfg:DiscountedCashFlowsValuationTechniqueMember 2023-03-31 0001335730 srt:MinimumMember us-gaap:MeasurementInputDiscountRateMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:ResidentialMortgageBackedSecuritiesMember mfg:DiscountedCashFlowsValuationTechniqueMember 2023-03-31 0001335730 srt:MaximumMember mfg:MeasurementInputRecoveryRateMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:ResidentialMortgageBackedSecuritiesMember mfg:DiscountedCashFlowsValuationTechniqueMember 2023-03-31 0001335730 srt:MinimumMember mfg:MeasurementInputRecoveryRateMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:ResidentialMortgageBackedSecuritiesMember mfg:DiscountedCashFlowsValuationTechniqueMember 2023-03-31 0001335730 srt:MaximumMember us-gaap:MeasurementInputDefaultRateMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:ResidentialMortgageBackedSecuritiesMember mfg:DiscountedCashFlowsValuationTechniqueMember 2023-03-31 0001335730 srt:MinimumMember us-gaap:MeasurementInputDefaultRateMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:ResidentialMortgageBackedSecuritiesMember mfg:DiscountedCashFlowsValuationTechniqueMember 2023-03-31 0001335730 srt:MaximumMember us-gaap:MeasurementInputPrepaymentRateMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:ResidentialMortgageBackedSecuritiesMember mfg:DiscountedCashFlowsValuationTechniqueMember 2023-03-31 0001335730 srt:MinimumMember us-gaap:MeasurementInputPrepaymentRateMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:ResidentialMortgageBackedSecuritiesMember mfg:DiscountedCashFlowsValuationTechniqueMember 2023-03-31 0001335730 srt:MinimumMember us-gaap:MeasurementInputDefaultRateMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:AllOtherCorporateBondsMember mfg:DiscountedCashFlowsValuationTechniqueMember 2023-03-31 0001335730 srt:MaximumMember us-gaap:MeasurementInputPrepaymentRateMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:AllOtherCorporateBondsMember mfg:DiscountedCashFlowsValuationTechniqueMember 2023-03-31 0001335730 srt:MinimumMember us-gaap:MeasurementInputPrepaymentRateMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:AllOtherCorporateBondsMember mfg:DiscountedCashFlowsValuationTechniqueMember 2023-03-31 0001335730 srt:WeightedAverageMember us-gaap:MeasurementInputDiscountRateMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:ResidentialMortgageBackedSecuritiesMember mfg:DiscountedCashFlowsValuationTechniqueMember 2023-03-31 0001335730 srt:WeightedAverageMember mfg:MeasurementInputRecoveryRateMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:ResidentialMortgageBackedSecuritiesMember mfg:DiscountedCashFlowsValuationTechniqueMember 2023-03-31 0001335730 srt:WeightedAverageMember us-gaap:MeasurementInputDefaultRateMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:ResidentialMortgageBackedSecuritiesMember mfg:DiscountedCashFlowsValuationTechniqueMember 2023-03-31 0001335730 srt:WeightedAverageMember us-gaap:MeasurementInputPrepaymentRateMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:ResidentialMortgageBackedSecuritiesMember mfg:DiscountedCashFlowsValuationTechniqueMember 2023-03-31 0001335730 srt:WeightedAverageMember mfg:MeasurementInputDiscountRate1Member mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:AllOtherCorporateBondsMember mfg:DiscountedCashFlowsValuationTechniqueMember 2023-03-31 0001335730 srt:WeightedAverageMember us-gaap:MeasurementInputDiscountRateMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:AllOtherCorporateBondsMember mfg:DiscountedCashFlowsValuationTechniqueMember 2023-03-31 0001335730 srt:WeightedAverageMember mfg:MeasurementInputRecoveryRateMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:AllOtherCorporateBondsMember mfg:DiscountedCashFlowsValuationTechniqueMember 2023-03-31 0001335730 srt:WeightedAverageMember us-gaap:MeasurementInputDefaultRateMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:AllOtherCorporateBondsMember mfg:DiscountedCashFlowsValuationTechniqueMember 2023-03-31 0001335730 srt:WeightedAverageMember us-gaap:MeasurementInputPrepaymentRateMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:AllOtherCorporateBondsMember mfg:DiscountedCashFlowsValuationTechniqueMember 2023-03-31 0001335730 srt:MaximumMember mfg:MeasurementInputDiscountRate1Member mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:AllOtherCorporateBondsMember mfg:DiscountedCashFlowsValuationTechniqueMember 2023-03-31 0001335730 srt:MinimumMember mfg:MeasurementInputDiscountRate1Member mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:AllOtherCorporateBondsMember mfg:DiscountedCashFlowsValuationTechniqueMember 2023-03-31 0001335730 srt:MaximumMember us-gaap:MeasurementInputDiscountRateMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:AllOtherCorporateBondsMember mfg:DiscountedCashFlowsValuationTechniqueMember 2023-03-31 0001335730 srt:MinimumMember us-gaap:MeasurementInputDiscountRateMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:AllOtherCorporateBondsMember mfg:DiscountedCashFlowsValuationTechniqueMember 2023-03-31 0001335730 srt:MaximumMember mfg:MeasurementInputRecoveryRateMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:AllOtherCorporateBondsMember mfg:DiscountedCashFlowsValuationTechniqueMember 2023-03-31 0001335730 srt:MinimumMember mfg:MeasurementInputRecoveryRateMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:AllOtherCorporateBondsMember mfg:DiscountedCashFlowsValuationTechniqueMember 2023-03-31 0001335730 srt:MaximumMember us-gaap:MeasurementInputDefaultRateMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:AllOtherCorporateBondsMember mfg:DiscountedCashFlowsValuationTechniqueMember 2023-03-31 0001335730 us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMember mfg:MizuhoFinancialGroupIncMember 2023-03-31 0001335730 us-gaap:HeldtomaturitySecuritiesMember us-gaap:DebtSecuritiesMember us-gaap:MortgageBackedSecuritiesOtherMember 2023-03-31 0001335730 us-gaap:HeldtomaturitySecuritiesMember us-gaap:DebtSecuritiesMember 2023-03-31 0001335730 mfg:GovernmentBondsMember us-gaap:DebtSecuritiesMember us-gaap:HeldtomaturitySecuritiesMember 2023-03-31 0001335730 srt:MaximumMember mfg:MeasurementInputIRIRCorrelationMember us-gaap:DerivativeMember mfg:InternalValuationModelMember us-gaap:InterestRateContractMember 2023-03-31 0001335730 srt:MinimumMember mfg:MeasurementInputIRIRCorrelationMember us-gaap:DerivativeMember mfg:InternalValuationModelMember us-gaap:InterestRateContractMember 2023-03-31 0001335730 srt:MaximumMember mfg:MeasurementInputFXFXCorrelationMember us-gaap:DerivativeMember mfg:InternalValuationModelMember us-gaap:ForeignExchangeContractMember 2023-03-31 0001335730 srt:MinimumMember mfg:MeasurementInputFXFXCorrelationMember us-gaap:DerivativeMember mfg:InternalValuationModelMember us-gaap:ForeignExchangeContractMember 2023-03-31 0001335730 srt:MaximumMember mfg:MeasurementInputFXIRCorrelationMember us-gaap:DerivativeMember mfg:InternalValuationModelMember us-gaap:ForeignExchangeContractMember 2023-03-31 0001335730 srt:MinimumMember mfg:MeasurementInputFXIRCorrelationMember us-gaap:DerivativeMember mfg:InternalValuationModelMember us-gaap:ForeignExchangeContractMember 2023-03-31 0001335730 srt:WeightedAverageMember mfg:MeasurementInputIRIRCorrelationMember us-gaap:DerivativeMember mfg:InternalValuationModelMember us-gaap:InterestRateContractMember 2023-03-31 0001335730 srt:WeightedAverageMember us-gaap:DerivativeMember mfg:InternalValuationModelMember us-gaap:MeasurementInputDefaultRateMember us-gaap:CreditRiskContractMember 2023-03-31 0001335730 srt:MinimumMember us-gaap:DerivativeMember mfg:InternalValuationModelMember mfg:MeasurementInputCommodityVolatilityMember mfg:OtherContractsMember 2023-03-31 0001335730 srt:MaximumMember us-gaap:DerivativeMember mfg:InternalValuationModelMember mfg:MeasurementInputCommodityVolatilityMember mfg:OtherContractsMember 2023-03-31 0001335730 srt:WeightedAverageMember us-gaap:DerivativeMember mfg:InternalValuationModelMember mfg:MeasurementInputCommodityVolatilityMember mfg:OtherContractsMember 2023-03-31 0001335730 srt:MaximumMember us-gaap:DerivativeMember mfg:InternalValuationModelMember us-gaap:MeasurementInputDefaultRateMember us-gaap:CreditRiskContractMember 2023-03-31 0001335730 srt:MinimumMember us-gaap:DerivativeMember mfg:InternalValuationModelMember us-gaap:MeasurementInputDefaultRateMember us-gaap:CreditRiskContractMember 2023-03-31 0001335730 srt:WeightedAverageMember mfg:MeasurementInputEquityVolatilityMember us-gaap:DerivativeMember mfg:InternalValuationModelMember us-gaap:EquityContractMember 2023-03-31 0001335730 srt:WeightedAverageMember mfg:MeasurementInputEquityCorrelationMember us-gaap:DerivativeMember mfg:InternalValuationModelMember us-gaap:EquityContractMember 2023-03-31 0001335730 srt:WeightedAverageMember mfg:MeasurementInputEquityFXCorrelationMember us-gaap:DerivativeMember mfg:InternalValuationModelMember us-gaap:EquityContractMember 2023-03-31 0001335730 srt:WeightedAverageMember mfg:MeasurementInputEquityIRCorrelationMember us-gaap:DerivativeMember mfg:InternalValuationModelMember us-gaap:EquityContractMember 2023-03-31 0001335730 srt:MaximumMember mfg:MeasurementInputEquityVolatilityMember us-gaap:DerivativeMember mfg:InternalValuationModelMember us-gaap:EquityContractMember 2023-03-31 0001335730 srt:MinimumMember mfg:MeasurementInputEquityVolatilityMember us-gaap:DerivativeMember mfg:InternalValuationModelMember us-gaap:EquityContractMember 2023-03-31 0001335730 srt:MaximumMember mfg:MeasurementInputEquityCorrelationMember us-gaap:DerivativeMember mfg:InternalValuationModelMember us-gaap:EquityContractMember 2023-03-31 0001335730 srt:MinimumMember mfg:MeasurementInputEquityCorrelationMember us-gaap:DerivativeMember mfg:InternalValuationModelMember us-gaap:EquityContractMember 2023-03-31 0001335730 srt:MaximumMember mfg:MeasurementInputEquityFXCorrelationMember us-gaap:DerivativeMember mfg:InternalValuationModelMember us-gaap:EquityContractMember 2023-03-31 0001335730 srt:MinimumMember mfg:MeasurementInputEquityFXCorrelationMember us-gaap:DerivativeMember mfg:InternalValuationModelMember us-gaap:EquityContractMember 2023-03-31 0001335730 srt:MaximumMember mfg:MeasurementInputEquityIRCorrelationMember us-gaap:DerivativeMember mfg:InternalValuationModelMember us-gaap:EquityContractMember 2023-03-31 0001335730 srt:MinimumMember mfg:MeasurementInputEquityIRCorrelationMember us-gaap:DerivativeMember mfg:InternalValuationModelMember us-gaap:EquityContractMember 2023-03-31 0001335730 srt:WeightedAverageMember mfg:MeasurementInputFXFXCorrelationMember us-gaap:DerivativeMember mfg:InternalValuationModelMember us-gaap:ForeignExchangeContractMember 2023-03-31 0001335730 srt:WeightedAverageMember mfg:MeasurementInputFXIRCorrelationMember us-gaap:DerivativeMember mfg:InternalValuationModelMember us-gaap:ForeignExchangeContractMember 2023-03-31 0001335730 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsNonrecurringMember 2023-03-31 0001335730 us-gaap:CarryingReportedAmountFairValueDisclosureMember 2023-03-31 0001335730 us-gaap:EstimateOfFairValueFairValueDisclosureMember 2023-03-31 0001335730 us-gaap:FairValueInputsLevel1Member us-gaap:EstimateOfFairValueFairValueDisclosureMember 2023-03-31 0001335730 us-gaap:FairValueInputsLevel2Member us-gaap:EstimateOfFairValueFairValueDisclosureMember 2023-03-31 0001335730 srt:MaximumMember mfg:InternalValuationModelMember mfg:MeasurementInputFXIRCorrelationMember us-gaap:LongTermDebtMember 2023-03-31 0001335730 srt:MinimumMember mfg:InternalValuationModelMember mfg:MeasurementInputFXFXCorrelationMember us-gaap:LongTermDebtMember 2023-03-31 0001335730 srt:MaximumMember mfg:InternalValuationModelMember mfg:MeasurementInputFXFXCorrelationMember us-gaap:LongTermDebtMember 2023-03-31 0001335730 srt:MinimumMember mfg:InternalValuationModelMember mfg:MeasurementInputEquityIRCorrelationMember us-gaap:LongTermDebtMember 2023-03-31 0001335730 srt:MaximumMember mfg:InternalValuationModelMember mfg:MeasurementInputEquityIRCorrelationMember us-gaap:LongTermDebtMember 2023-03-31 0001335730 srt:MinimumMember mfg:InternalValuationModelMember mfg:MeasurementInputEquityFXCorrelationMember us-gaap:LongTermDebtMember 2023-03-31 0001335730 srt:MaximumMember mfg:InternalValuationModelMember mfg:MeasurementInputEquityFXCorrelationMember us-gaap:LongTermDebtMember 2023-03-31 0001335730 srt:MinimumMember mfg:InternalValuationModelMember mfg:MeasurementInputEquityCorrelationMember us-gaap:LongTermDebtMember 2023-03-31 0001335730 srt:MaximumMember mfg:InternalValuationModelMember mfg:MeasurementInputEquityCorrelationMember us-gaap:LongTermDebtMember 2023-03-31 0001335730 srt:MinimumMember mfg:InternalValuationModelMember mfg:MeasurementInputEquityVolatilityMember us-gaap:LongTermDebtMember 2023-03-31 0001335730 srt:MaximumMember mfg:InternalValuationModelMember mfg:MeasurementInputEquityVolatilityMember us-gaap:LongTermDebtMember 2023-03-31 0001335730 srt:MinimumMember mfg:InternalValuationModelMember us-gaap:MeasurementInputDefaultRateMember us-gaap:LongTermDebtMember 2023-03-31 0001335730 srt:MaximumMember mfg:InternalValuationModelMember us-gaap:MeasurementInputDefaultRateMember us-gaap:LongTermDebtMember 2023-03-31 0001335730 srt:MinimumMember mfg:InternalValuationModelMember mfg:MeasurementInputCreditCorrelationMember us-gaap:LongTermDebtMember 2023-03-31 0001335730 srt:MaximumMember mfg:InternalValuationModelMember mfg:MeasurementInputCreditCorrelationMember us-gaap:LongTermDebtMember 2023-03-31 0001335730 srt:WeightedAverageMember mfg:InternalValuationModelMember mfg:MeasurementInputIRIRCorrelationMember us-gaap:LongTermDebtMember 2023-03-31 0001335730 srt:WeightedAverageMember mfg:InternalValuationModelMember mfg:MeasurementInputFXIRCorrelationMember us-gaap:LongTermDebtMember 2023-03-31 0001335730 srt:WeightedAverageMember mfg:InternalValuationModelMember mfg:MeasurementInputFXFXCorrelationMember us-gaap:LongTermDebtMember 2023-03-31 0001335730 srt:WeightedAverageMember mfg:InternalValuationModelMember mfg:MeasurementInputEquityIRCorrelationMember us-gaap:LongTermDebtMember 2023-03-31 0001335730 srt:WeightedAverageMember mfg:InternalValuationModelMember mfg:MeasurementInputEquityFXCorrelationMember us-gaap:LongTermDebtMember 2023-03-31 0001335730 srt:WeightedAverageMember mfg:InternalValuationModelMember mfg:MeasurementInputEquityCorrelationMember us-gaap:LongTermDebtMember 2023-03-31 0001335730 srt:WeightedAverageMember mfg:InternalValuationModelMember mfg:MeasurementInputEquityVolatilityMember us-gaap:LongTermDebtMember 2023-03-31 0001335730 srt:WeightedAverageMember mfg:InternalValuationModelMember us-gaap:MeasurementInputDefaultRateMember us-gaap:LongTermDebtMember 2023-03-31 0001335730 srt:WeightedAverageMember mfg:InternalValuationModelMember mfg:MeasurementInputCreditCorrelationMember us-gaap:LongTermDebtMember 2023-03-31 0001335730 srt:MinimumMember mfg:InternalValuationModelMember mfg:MeasurementInputIRIRCorrelationMember us-gaap:LongTermDebtMember 2023-03-31 0001335730 srt:MaximumMember mfg:InternalValuationModelMember mfg:MeasurementInputIRIRCorrelationMember us-gaap:LongTermDebtMember 2023-03-31 0001335730 srt:MinimumMember mfg:InternalValuationModelMember mfg:MeasurementInputFXIRCorrelationMember us-gaap:LongTermDebtMember 2023-03-31 0001335730 us-gaap:SecuritiesInvestmentMember us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMember 2023-03-31 0001335730 mfg:TrustAccountsMember us-gaap:VariableInterestEntityPrimaryBeneficiaryMember 2023-03-31 0001335730 mfg:AssetBackedSecuritizationsMember us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMember 2023-03-31 0001335730 us-gaap:VariableInterestEntityPrimaryBeneficiaryMember 2023-03-31 0001335730 mfg:InvestmentsInSecuritizationProductsMember us-gaap:VariableInterestEntityPrimaryBeneficiaryMember 2023-03-31 0001335730 us-gaap:VariableInterestEntityPrimaryBeneficiaryMember us-gaap:AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember 2023-03-31 0001335730 us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMember 2023-03-31 0001335730 us-gaap:VariableInterestEntityPrimaryBeneficiaryMember us-gaap:SecuritiesInvestmentMember 2023-03-31 0001335730 mfg:AssetBackedSecuritizationsMember us-gaap:VariableInterestEntityPrimaryBeneficiaryMember 2023-03-31 0001335730 us-gaap:AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMember 2023-03-31 0001335730 mfg:InvestmentsInSecuritizationProductsMember us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMember 2023-03-31 0001335730 mfg:TrustAccountsMember us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMember 2023-03-31 0001335730 srt:MinimumMember 2023-03-31 0001335730 srt:MaximumMember 2023-03-31 0001335730 srt:WeightedAverageMember 2023-03-31 0001335730 mfg:CommercialPaperAndCorporateBondsMember 2023-03-31 0001335730 mfg:JapaneseGovernmentBondsLocalGovernmentBondsMember 2023-03-31 0001335730 mfg:EquitySecuritiesInSecuredBorrowingsMember 2023-03-31 0001335730 mfg:ForeignGovernmentBondsAndForeignAgencyMortgageBackedSecuritiesMember 2023-03-31 0001335730 mfg:OtherSecuritiesMember 2023-03-31 0001335730 us-gaap:SeniorDebtObligationsMember 2023-03-31 0001335730 us-gaap:FairValueInputsLevel3Member us-gaap:EstimateOfFairValueFairValueDisclosureMember 2023-03-31 0001335730 us-gaap:InterestRateContractMember 2023-03-31 0001335730 us-gaap:CreditRiskContractMember 2023-03-31 0001335730 us-gaap:EquityContractMember 2023-03-31 0001335730 us-gaap:ForeignExchangeContractMember 2023-03-31 0001335730 us-gaap:OtherContractMember 2023-03-31 0001335730 us-gaap:AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember 2023-03-31 0001335730 us-gaap:SecuritiesInvestmentMember 2023-03-31 0001335730 mfg:AssetBackedSecuritizationsMember 2023-03-31 0001335730 mfg:InvestmentsInSecuritizationProductsMember 2023-03-31 0001335730 mfg:TrustAccountsMember 2023-03-31 0001335730 us-gaap:InterestRateContractMember us-gaap:NondesignatedMember 2023-03-31 0001335730 us-gaap:CreditRiskContractMember us-gaap:NondesignatedMember 2023-03-31 0001335730 us-gaap:NondesignatedMember 2023-03-31 0001335730 us-gaap:OtherContractMember us-gaap:NondesignatedMember 2023-03-31 0001335730 us-gaap:NondesignatedMember us-gaap:ForeignExchangeContractMember 2023-03-31 0001335730 us-gaap:EquityContractMember us-gaap:NondesignatedMember 2023-03-31 0001335730 us-gaap:DesignatedAsHedgingInstrumentMember us-gaap:EquityContractMember 2023-03-31 0001335730 us-gaap:DesignatedAsHedgingInstrumentMember us-gaap:CreditRiskContractMember 2023-03-31 0001335730 us-gaap:DesignatedAsHedgingInstrumentMember us-gaap:OtherContractMember 2023-03-31 0001335730 us-gaap:DesignatedAsHedgingInstrumentMember 2023-03-31 0001335730 us-gaap:DesignatedAsHedgingInstrumentMember us-gaap:InterestRateContractMember 2023-03-31 0001335730 us-gaap:DesignatedAsHedgingInstrumentMember us-gaap:ForeignExchangeContractMember 2023-03-31 0001335730 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 us-gaap:MunicipalBondsMember us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 mfg:GovernmentBondsMember us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 mfg:GovernmentBondsMember us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 mfg:GovernmentBondsMember us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 us-gaap:MunicipalBondsMember us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 us-gaap:USTreasuryAndGovernmentShorttermDebtSecuritiesMember us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 us-gaap:USTreasuryAndGovernmentShorttermDebtSecuritiesMember us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 us-gaap:USTreasuryAndGovernmentShorttermDebtSecuritiesMember us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 mfg:ForeignGovernmentBondsMember us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 mfg:ForeignGovernmentBondsMember us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 mfg:ForeignGovernmentBondsMember us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 us-gaap:MortgageBackedSecuritiesOtherMember us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 us-gaap:MortgageBackedSecuritiesOtherMember us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 mfg:CertificatesOfDepositAndCommercialPaperMember us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 mfg:CertificatesOfDepositAndCommercialPaperMember us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 us-gaap:AllOtherCorporateBondsMember us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 us-gaap:AllOtherCorporateBondsMember us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 us-gaap:AllOtherCorporateBondsMember us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 us-gaap:EquitySecuritiesMember us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 us-gaap:EquitySecuritiesMember us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 us-gaap:EquitySecuritiesMember us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 us-gaap:EquitySecuritiesMember us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 us-gaap:InterestRateContractMember us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 us-gaap:InterestRateContractMember us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 us-gaap:InterestRateContractMember us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 us-gaap:InterestRateContractMember us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 us-gaap:ForeignExchangeContractMember us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 us-gaap:ForeignExchangeContractMember us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 us-gaap:ForeignExchangeContractMember us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 us-gaap:EquityContractMember us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 us-gaap:EquityContractMember us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 us-gaap:EquityContractMember us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 us-gaap:EquityContractMember us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 us-gaap:CreditRiskContractMember us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 us-gaap:CreditRiskContractMember us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 us-gaap:CreditRiskContractMember us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 us-gaap:OtherContractMember us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 us-gaap:OtherContractMember us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 us-gaap:OtherContractMember us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 us-gaap:OtherContractMember us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 us-gaap:ResidentialMortgageBackedSecuritiesMember us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 us-gaap:ResidentialMortgageBackedSecuritiesMember us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 us-gaap:ResidentialMortgageBackedSecuritiesMember us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 us-gaap:CommercialMortgageBackedSecuritiesMember us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 us-gaap:CommercialMortgageBackedSecuritiesMember us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 mfg:JapaneseCorporateBondsMember us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 mfg:JapaneseCorporateBondsMember us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 mfg:JapaneseCorporateBondsMember us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 mfg:NonJapaneseCorporateBondsMember us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 mfg:NonJapaneseCorporateBondsMember us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 mfg:NonJapaneseCorporateBondsMember us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember 2023-03-31 0001335730 us-gaap:AccruedIncomeReceivableMember 2023-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:PassMember us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:SmallAndMediumSizedCompaniesMember 2023-03-31 0001335730 us-gaap:PassMember us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:HousingLoanMember 2023-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:SpecialMentionMember us-gaap:GeographicDistributionDomesticMember mfg:SoverignMember 2023-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:SpecialMentionMember us-gaap:GeographicDistributionForeignMember mfg:RetailRatingMember 2023-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember mfg:NonAccrualLoansMember us-gaap:GeographicDistributionForeignMember mfg:BanksAndFinancialInstitutionsMember 2023-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:SpecialMentionMember us-gaap:GeographicDistributionDomesticMember mfg:BanksAndFinancialInstitutionsMember 2023-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:SpecialMentionMember us-gaap:GeographicDistributionForeignMember mfg:SoverignMember 2023-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:SpecialMentionMember us-gaap:GeographicDistributionForeignMember mfg:CorporateRatingMember 2023-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionDomesticMember 2023-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:PassMember us-gaap:GeographicDistributionForeignMember mfg:BanksAndFinancialInstitutionsMember 2023-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:SpecialMentionMember us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:SmallAndMediumSizedCompaniesMember 2023-03-31 0001335730 us-gaap:SpecialMentionMember us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:OtherMember 2023-03-31 0001335730 mfg:NonAccrualLoansMember us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:HousingLoanMember 2023-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:SpecialMentionMember us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:LargeCompaniesMember 2023-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember mfg:NonAccrualLoansMember us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:SmallAndMediumSizedCompaniesMember 2023-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember 2023-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:PassMember us-gaap:GeographicDistributionForeignMember mfg:CorporateRatingMember 2023-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:PassMember us-gaap:GeographicDistributionForeignMember mfg:SoverignMember 2023-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember mfg:NonAccrualLoansMember us-gaap:GeographicDistributionForeignMember mfg:RetailRatingMember 2023-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:SpecialMentionMember us-gaap:GeographicDistributionForeignMember mfg:BanksAndFinancialInstitutionsMember 2023-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember mfg:NonAccrualLoansMember us-gaap:GeographicDistributionDomesticMember mfg:BanksAndFinancialInstitutionsMember 2023-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:PassMember us-gaap:GeographicDistributionDomesticMember mfg:BanksAndFinancialInstitutionsMember 2023-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionForeignMember 2023-03-31 0001335730 us-gaap:PassMember us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:OtherMember 2023-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:PassMember mfg:CorporateRatingMember us-gaap:GeographicDistributionDomesticMember mfg:LargeCompaniesMember 2023-03-31 0001335730 us-gaap:SpecialMentionMember us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:HousingLoanMember 2023-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember mfg:NonAccrualLoansMember us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:LargeCompaniesMember 2023-03-31 0001335730 mfg:NonAccrualLoansMember us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:OtherMember 2023-03-31 0001335730 mfg:CorporateRatingMember us-gaap:GeographicDistributionForeignMember mfg:NonAccrualLoansMember mfg:FinancingReceivablesNotImpairedMember 2023-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:PassMember us-gaap:GeographicDistributionDomesticMember mfg:SoverignMember 2023-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember mfg:NonAccrualLoansMember us-gaap:GeographicDistributionDomesticMember mfg:SoverignMember 2023-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionForeignMember mfg:SoverignMember mfg:NonAccrualLoansMember 2023-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:PassMember us-gaap:GeographicDistributionForeignMember mfg:RetailRatingMember 2023-03-31 0001335730 mfg:SubjectToEnforceableMasterNettingArragementMember 2023-03-31 0001335730 mfg:NetOfAllowanceForCreditLossMember 2023-03-31 0001335730 us-gaap:AccruedIncomeReceivableMember mfg:AvailableForSaleAndHeldToMaturitySecuritiesMember 2023-03-31 0001335730 mfg:FinancingReceivablesImpairedMember 2023-03-31 0001335730 mfg:SoverignMember mfg:TotalPastDueMember us-gaap:GeographicDistributionDomesticMember 2023-03-31 0001335730 us-gaap:FinancingReceivables60To89DaysPastDueMember 2023-03-31 0001335730 mfg:BanksAndFinancialInstitutionsMember us-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember us-gaap:GeographicDistributionDomesticMember 2023-03-31 0001335730 mfg:BanksAndFinancialInstitutionsMember mfg:TotalMember us-gaap:GeographicDistributionDomesticMember 2023-03-31 0001335730 us-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember us-gaap:GeographicDistributionDomesticMember 2023-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:TotalMember 2023-03-31 0001335730 us-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember us-gaap:GeographicDistributionForeignMember 2023-03-31 0001335730 mfg:TotalMember us-gaap:GeographicDistributionForeignMember 2023-03-31 0001335730 mfg:TotalPastDueMember 2023-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:TotalPastDueMember mfg:LargeCompaniesMember 2023-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember us-gaap:FinancingReceivables30To59DaysPastDueMember mfg:SmallAndMediumSizedCompaniesMember 2023-03-31 0001335730 mfg:CorporateRatingMember us-gaap:GeographicDistributionDomesticMember mfg:TotalPastDueMember mfg:SmallAndMediumSizedCompaniesMember 2023-03-31 0001335730 mfg:HousingLoanMember mfg:RetailRatingMember us-gaap:GeographicDistributionDomesticMember us-gaap:FinancingReceivables30To59DaysPastDueMember 2023-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:TotalPastDueMember mfg:HousingLoanMember 2023-03-31 0001335730 us-gaap:FinancingReceivables30To59DaysPastDueMember mfg:OtherMember mfg:RetailRatingMember us-gaap:GeographicDistributionDomesticMember 2023-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:TotalPastDueMember mfg:OtherMember 2023-03-31 0001335730 mfg:SoverignMember us-gaap:FinancingReceivables30To59DaysPastDueMember us-gaap:GeographicDistributionDomesticMember 2023-03-31 0001335730 mfg:SoverignMember us-gaap:FinancingReceivables60To89DaysPastDueMember us-gaap:GeographicDistributionDomesticMember 2023-03-31 0001335730 mfg:OtherMember us-gaap:GeographicDistributionDomesticMember mfg:CurrentMember mfg:RetailRatingMember 2023-03-31 0001335730 us-gaap:FinancingReceivables60To89DaysPastDueMember mfg:OtherMember mfg:RetailRatingMember us-gaap:GeographicDistributionDomesticMember 2023-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:CurrentMember mfg:HousingLoanMember 2023-03-31 0001335730 mfg:HousingLoanMember mfg:RetailRatingMember us-gaap:GeographicDistributionDomesticMember us-gaap:FinancingReceivables60To89DaysPastDueMember 2023-03-31 0001335730 mfg:CorporateRatingMember us-gaap:GeographicDistributionDomesticMember mfg:CurrentMember mfg:SmallAndMediumSizedCompaniesMember 2023-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember us-gaap:FinancingReceivables60To89DaysPastDueMember mfg:SmallAndMediumSizedCompaniesMember 2023-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:CurrentMember mfg:LargeCompaniesMember 2023-03-31 0001335730 mfg:CurrentMember 2023-03-31 0001335730 us-gaap:FinancingReceivables30To59DaysPastDueMember 2023-03-31 0001335730 mfg:TotalPastDueMember us-gaap:GeographicDistributionForeignMember 2023-03-31 0001335730 us-gaap:FinancingReceivables30To59DaysPastDueMember us-gaap:GeographicDistributionForeignMember 2023-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:TotalPastDueMember 2023-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember us-gaap:FinancingReceivables30To59DaysPastDueMember 2023-03-31 0001335730 mfg:BanksAndFinancialInstitutionsMember mfg:TotalPastDueMember us-gaap:GeographicDistributionDomesticMember 2023-03-31 0001335730 mfg:BanksAndFinancialInstitutionsMember us-gaap:FinancingReceivables30To59DaysPastDueMember us-gaap:GeographicDistributionDomesticMember 2023-03-31 0001335730 mfg:SoverignMember mfg:CurrentMember us-gaap:GeographicDistributionDomesticMember 2023-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember us-gaap:FinancingReceivables30To59DaysPastDueMember mfg:LargeCompaniesMember 2023-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember us-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember mfg:HousingLoanMember 2023-03-31 0001335730 mfg:LargeCompaniesMember us-gaap:FinancingReceivables60To89DaysPastDueMember mfg:CorporateRatingMember us-gaap:GeographicDistributionDomesticMember 2023-03-31 0001335730 mfg:SoverignMember mfg:TotalMember us-gaap:GeographicDistributionDomesticMember 2023-03-31 0001335730 mfg:LargeCompaniesMember us-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember mfg:CorporateRatingMember us-gaap:GeographicDistributionDomesticMember 2023-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CurrentMember mfg:BanksAndFinancialInstitutionsMember 2023-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember us-gaap:FinancingReceivables60To89DaysPastDueMember 2023-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CurrentMember 2023-03-31 0001335730 mfg:BanksAndFinancialInstitutionsMember us-gaap:FinancingReceivables60To89DaysPastDueMember us-gaap:GeographicDistributionDomesticMember 2023-03-31 0001335730 mfg:CurrentMember us-gaap:GeographicDistributionForeignMember 2023-03-31 0001335730 us-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember 2023-03-31 0001335730 mfg:TotalMember 2023-03-31 0001335730 mfg:LargeCompaniesMember mfg:TotalMember mfg:CorporateRatingMember us-gaap:GeographicDistributionDomesticMember 2023-03-31 0001335730 us-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:SmallAndMediumSizedCompaniesMember 2023-03-31 0001335730 mfg:CorporateRatingMember us-gaap:GeographicDistributionDomesticMember mfg:TotalMember mfg:SmallAndMediumSizedCompaniesMember 2023-03-31 0001335730 us-gaap:FinancingReceivables60To89DaysPastDueMember us-gaap:GeographicDistributionForeignMember 2023-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:TotalMember mfg:HousingLoanMember 2023-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember us-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember mfg:OtherMember 2023-03-31 0001335730 mfg:OtherMember mfg:TotalMember mfg:RetailRatingMember us-gaap:GeographicDistributionDomesticMember 2023-03-31 0001335730 mfg:SoverignMember us-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember us-gaap:GeographicDistributionDomesticMember 2023-03-31 0001335730 mfg:ClassSixteenPreferredStockMember 2023-09-30 0001335730 mfg:ClassFourteenPreferredStockMember 2023-09-30 0001335730 mfg:ClassFifteenPreferredStockMember 2023-09-30 0001335730 us-gaap:MaturityOver90DaysMember 2023-09-30 0001335730 mfg:MaturityOvernightAndOpenMember 2023-09-30 0001335730 mfg:Maturity31To90DaysMember 2023-09-30 0001335730 us-gaap:MaturityUpTo30DaysMember 2023-09-30 0001335730 us-gaap:MortgageBackedSecuritiesOtherMember mfg:DomesticGovernmentSponsoredEnterprisesDebtSecuritiesMember us-gaap:DebtSecuritiesMember 2023-09-30 0001335730 mfg:MizuhoFinancialGroupInc.Member 2023-09-30 0001335730 us-gaap:FinancialGuaranteeMember 2023-09-30 0001335730 mfg:GuaranteesForRepaymentOfTrustPrincipalMember 2023-09-30 0001335730 us-gaap:MarketValueGuaranteeMember 2023-09-30 0001335730 mfg:GuaranteesOnTrustAccountsMember 2023-09-30 0001335730 us-gaap:PerformanceGuaranteeMember 2023-09-30 0001335730 us-gaap:GuaranteeTypeOtherMember 2023-09-30 0001335730 us-gaap:PaymentGuaranteeMember 2023-09-30 0001335730 mfg:ExpirationPeriodAfterFiveYearsMember 2023-09-30 0001335730 mfg:ExpirationPeriodOneYearOrLessMember 2023-09-30 0001335730 mfg:ExpirationPeriodAfterOneYearThroughFiveYearsMember 2023-09-30 0001335730 mfg:DebtInstrumentMember 2023-09-30 0001335730 us-gaap:MortgageBackedSecuritiesOtherMember mfg:ForeignAgencyMortgageBackedSecuritiesMember us-gaap:DebtSecuritiesMember 2023-09-30 0001335730 mfg:NegotiableCertificatesOfDepositsAssetBackedSecuritiesAndCollateralLoanObligationsMember us-gaap:DebtSecuritiesMember 2023-09-30 0001335730 us-gaap:CommercialMortgageBackedSecuritiesMember us-gaap:DebtSecuritiesMember us-gaap:AvailableforsaleSecuritiesMember 2023-09-30 0001335730 us-gaap:AvailableforsaleSecuritiesMember us-gaap:DebtSecuritiesMember mfg:ForeignGovernmentBondsMember 2023-09-30 0001335730 us-gaap:DebtSecuritiesMember us-gaap:AvailableforsaleSecuritiesMember 2023-09-30 0001335730 mfg:GovernmentBondsMember us-gaap:DebtSecuritiesMember us-gaap:AvailableforsaleSecuritiesMember 2023-09-30 0001335730 us-gaap:MortgageBackedSecuritiesOtherMember us-gaap:DebtSecuritiesMember us-gaap:AvailableforsaleSecuritiesMember 2023-09-30 0001335730 us-gaap:AvailableforsaleSecuritiesMember us-gaap:DebtSecuritiesMember us-gaap:MunicipalBondsMember 2023-09-30 0001335730 us-gaap:AvailableforsaleSecuritiesMember us-gaap:DebtSecuritiesMember mfg:DomesticDebtSecuritiesMember 2023-09-30 0001335730 us-gaap:DebtSecuritiesMember us-gaap:ForeignCorporateDebtSecuritiesMember us-gaap:AvailableforsaleSecuritiesMember 2023-09-30 0001335730 us-gaap:USTreasuryAndGovernmentShorttermDebtSecuritiesMember us-gaap:DebtSecuritiesMember us-gaap:AvailableforsaleSecuritiesMember 2023-09-30 0001335730 us-gaap:ResidentialMortgageBackedSecuritiesMember us-gaap:DebtSecuritiesMember us-gaap:AvailableforsaleSecuritiesMember 2023-09-30 0001335730 us-gaap:DebtSecuritiesMember us-gaap:USTreasuryAndGovernmentShorttermDebtSecuritiesMember 2023-09-30 0001335730 mfg:GovernmentBondsMember us-gaap:DebtSecuritiesMember 2023-09-30 0001335730 us-gaap:MunicipalBondsMember us-gaap:DebtSecuritiesMember 2023-09-30 0001335730 us-gaap:MortgageBackedSecuritiesOtherMember us-gaap:DebtSecuritiesMember 2023-09-30 0001335730 us-gaap:DebtSecuritiesMember us-gaap:CommercialMortgageBackedSecuritiesMember 2023-09-30 0001335730 us-gaap:DebtSecuritiesMember mfg:DomesticDebtSecuritiesMember 2023-09-30 0001335730 mfg:ForeignGovernmentBondsMember us-gaap:DebtSecuritiesMember 2023-09-30 0001335730 us-gaap:ResidentialMortgageBackedSecuritiesMember us-gaap:DebtSecuritiesMember 2023-09-30 0001335730 us-gaap:ForeignCorporateDebtSecuritiesMember us-gaap:DebtSecuritiesMember 2023-09-30 0001335730 us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2023-09-30 0001335730 us-gaap:CommercialMortgageBackedSecuritiesMember mfg:AvailableForSaleAndTradingSecuritiesMember 2023-09-30 0001335730 mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:AllOtherCorporateBondsMember 2023-09-30 0001335730 us-gaap:DerivativeMember us-gaap:EquityContractMember 2023-09-30 0001335730 us-gaap:DerivativeMember us-gaap:ForeignExchangeContractMember 2023-09-30 0001335730 us-gaap:DerivativeMember us-gaap:InterestRateContractMember 2023-09-30 0001335730 us-gaap:CreditRiskContractMember us-gaap:DerivativeMember 2023-09-30 0001335730 mfg:ImpairedFinancingReceivablesWithNoRelatedAllowanceMember 2023-09-30 0001335730 mfg:MarketableEquitySecuritiesMember 2023-09-30 0001335730 mfg:MizuhoBankLimitedMember mfg:JapanGaapConsolidatedMember 2023-09-30 0001335730 mfg:JapanGaapUnconsolidatedAffiliatesMember mfg:MizuhoTrustBankingCompanyLimitedMember 2023-09-30 0001335730 mfg:JapanGaapConsolidatedMember mfg:MizuhoTrustBankingCompanyLimitedMember 2023-09-30 0001335730 mfg:MizuhoFinancialGroupIncMember mfg:JapanGaapConsolidatedMember 2023-09-30 0001335730 mfg:JapanGaapUnconsolidatedAffiliatesMember mfg:MizuhoBankLimitedMember 2023-09-30 0001335730 us-gaap:ExternalCreditRatingNonInvestmentGradeMember mfg:CreditRiskContractWrittenMember 2023-09-30 0001335730 mfg:CreditRiskContractWrittenMember 2023-09-30 0001335730 mfg:CreditRiskContractWrittenMember us-gaap:ExternalCreditRatingInvestmentGradeMember 2023-09-30 0001335730 mfg:CreditRiskContractPurchasedMember 2023-09-30 0001335730 us-gaap:RiskLevelLowMember mfg:PerformanceFinancialMarketValueAndOtherTypeGuaranteeMember 2023-09-30 0001335730 us-gaap:RiskLevelHighMember mfg:PerformanceFinancialMarketValueAndOtherTypeGuaranteeMember 2023-09-30 0001335730 mfg:PerformanceFinancialMarketValueAndOtherTypeGuaranteeMember 2023-09-30 0001335730 us-gaap:CommitmentsToExtendCreditMember 2023-09-30 0001335730 us-gaap:UnusedLinesOfCreditMember 2023-09-30 0001335730 us-gaap:LongTermDebtMember 2023-09-30 0001335730 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsNonrecurringMember 2023-09-30 0001335730 us-gaap:FairValueMeasurementsNonrecurringMember 2023-09-30 0001335730 us-gaap:PortionAtOtherThanFairValueFairValueDisclosureMember us-gaap:FairValueMeasurementsNonrecurringMember 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:LargeCompaniesMember 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:OtherMember 2023-09-30 0001335730 mfg:HousingLoanMember mfg:RetailRatingMember us-gaap:GeographicDistributionDomesticMember 2023-09-30 0001335730 us-gaap:GeographicDistributionForeignMember 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:SmallAndMediumSizedCompaniesMember 2023-09-30 0001335730 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsNonrecurringMember 2023-09-30 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:MeasurementInputPrepaymentRateMember srt:MinimumMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2023-09-30 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:MeasurementInputPrepaymentRateMember srt:MaximumMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2023-09-30 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:MeasurementInputDefaultRateMember srt:MinimumMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2023-09-30 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:MeasurementInputDefaultRateMember srt:MaximumMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2023-09-30 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember mfg:AvailableForSaleAndTradingSecuritiesMember mfg:MeasurementInputRecoveryRateMember srt:MinimumMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2023-09-30 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember mfg:AvailableForSaleAndTradingSecuritiesMember mfg:MeasurementInputRecoveryRateMember srt:MaximumMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2023-09-30 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:MeasurementInputDiscountRateMember srt:MinimumMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2023-09-30 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:MeasurementInputDiscountRateMember srt:MaximumMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2023-09-30 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:MeasurementInputPrepaymentRateMember srt:WeightedAverageMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2023-09-30 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:MeasurementInputDefaultRateMember srt:WeightedAverageMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2023-09-30 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember mfg:AvailableForSaleAndTradingSecuritiesMember mfg:MeasurementInputRecoveryRateMember srt:WeightedAverageMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2023-09-30 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:MeasurementInputDiscountRateMember srt:WeightedAverageMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2023-09-30 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember mfg:AvailableForSaleAndTradingSecuritiesMember mfg:MeasurementInputDiscountRate1Member srt:MinimumMember us-gaap:CommercialMortgageBackedSecuritiesMember 2023-09-30 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember mfg:AvailableForSaleAndTradingSecuritiesMember mfg:MeasurementInputDiscountRate1Member srt:MaximumMember us-gaap:CommercialMortgageBackedSecuritiesMember 2023-09-30 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember mfg:AvailableForSaleAndTradingSecuritiesMember mfg:MeasurementInputDiscountRate1Member srt:WeightedAverageMember us-gaap:CommercialMortgageBackedSecuritiesMember 2023-09-30 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:MeasurementInputPrepaymentRateMember srt:MinimumMember us-gaap:AllOtherCorporateBondsMember 2023-09-30 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:MeasurementInputPrepaymentRateMember srt:MaximumMember us-gaap:AllOtherCorporateBondsMember 2023-09-30 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:MeasurementInputDefaultRateMember srt:MinimumMember us-gaap:AllOtherCorporateBondsMember 2023-09-30 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:MeasurementInputDefaultRateMember srt:MaximumMember us-gaap:AllOtherCorporateBondsMember 2023-09-30 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember mfg:AvailableForSaleAndTradingSecuritiesMember mfg:MeasurementInputRecoveryRateMember srt:MinimumMember us-gaap:AllOtherCorporateBondsMember 2023-09-30 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember mfg:AvailableForSaleAndTradingSecuritiesMember mfg:MeasurementInputRecoveryRateMember srt:MaximumMember us-gaap:AllOtherCorporateBondsMember 2023-09-30 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:MeasurementInputDiscountRateMember srt:MinimumMember us-gaap:AllOtherCorporateBondsMember 2023-09-30 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:MeasurementInputDiscountRateMember srt:MaximumMember us-gaap:AllOtherCorporateBondsMember 2023-09-30 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember mfg:AvailableForSaleAndTradingSecuritiesMember mfg:MeasurementInputDiscountRate1Member srt:MinimumMember us-gaap:AllOtherCorporateBondsMember 2023-09-30 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember mfg:AvailableForSaleAndTradingSecuritiesMember mfg:MeasurementInputDiscountRate1Member srt:MaximumMember us-gaap:AllOtherCorporateBondsMember 2023-09-30 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:MeasurementInputPrepaymentRateMember srt:WeightedAverageMember us-gaap:AllOtherCorporateBondsMember 2023-09-30 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:MeasurementInputDefaultRateMember srt:WeightedAverageMember us-gaap:AllOtherCorporateBondsMember 2023-09-30 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember mfg:AvailableForSaleAndTradingSecuritiesMember mfg:MeasurementInputRecoveryRateMember srt:WeightedAverageMember us-gaap:AllOtherCorporateBondsMember 2023-09-30 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:MeasurementInputDiscountRateMember srt:WeightedAverageMember us-gaap:AllOtherCorporateBondsMember 2023-09-30 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember mfg:AvailableForSaleAndTradingSecuritiesMember mfg:MeasurementInputDiscountRate1Member srt:WeightedAverageMember us-gaap:AllOtherCorporateBondsMember 2023-09-30 0001335730 us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMember mfg:MizuhoFinancialGroupIncMember 2023-09-30 0001335730 mfg:OricoMember 2023-09-30 0001335730 mfg:JointStockCommercialBankForeignTradeOfVietnamMember 2023-09-30 0001335730 mfg:MizuhoLeasingCompanyLtdMember 2023-09-30 0001335730 mfg:MatthewInternationalCapitalManagementLlcMember 2023-09-30 0001335730 mfg:CustodyBankOfJapanLtdMember 2023-09-30 0001335730 mfg:RakutenSecuritiesIncMember 2023-09-30 0001335730 us-gaap:HeldtomaturitySecuritiesMember us-gaap:DebtSecuritiesMember 2023-09-30 0001335730 mfg:GovernmentBondsMember us-gaap:DebtSecuritiesMember us-gaap:HeldtomaturitySecuritiesMember 2023-09-30 0001335730 us-gaap:HeldtomaturitySecuritiesMember us-gaap:DebtSecuritiesMember us-gaap:MortgageBackedSecuritiesOtherMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:InterestRateContractMember us-gaap:DerivativeMember mfg:MeasurementInputIRIRCorrelationMember srt:MinimumMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:InterestRateContractMember us-gaap:DerivativeMember mfg:MeasurementInputIRIRCorrelationMember srt:MaximumMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:InterestRateContractMember us-gaap:DerivativeMember mfg:MeasurementInputIRIRCorrelationMember srt:WeightedAverageMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:ForeignExchangeContractMember us-gaap:DerivativeMember mfg:MeasurementInputFXIRCorrelationMember srt:MinimumMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:ForeignExchangeContractMember us-gaap:DerivativeMember mfg:MeasurementInputFXIRCorrelationMember srt:MaximumMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:ForeignExchangeContractMember us-gaap:DerivativeMember mfg:MeasurementInputFXFXCorrelationMember srt:MinimumMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:ForeignExchangeContractMember us-gaap:DerivativeMember mfg:MeasurementInputFXFXCorrelationMember srt:MaximumMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:ForeignExchangeContractMember us-gaap:DerivativeMember mfg:MeasurementInputFXIRCorrelationMember srt:WeightedAverageMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:ForeignExchangeContractMember us-gaap:DerivativeMember mfg:MeasurementInputFXFXCorrelationMember srt:WeightedAverageMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:EquityContractMember us-gaap:DerivativeMember mfg:MeasurementInputEquityIRCorrelationMember srt:MinimumMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:EquityContractMember us-gaap:DerivativeMember mfg:MeasurementInputEquityIRCorrelationMember srt:MaximumMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:EquityContractMember us-gaap:DerivativeMember mfg:MeasurementInputEquityFXCorrelationMember srt:MinimumMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:EquityContractMember us-gaap:DerivativeMember mfg:MeasurementInputEquityFXCorrelationMember srt:MaximumMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:EquityContractMember us-gaap:DerivativeMember mfg:MeasurementInputEquityCorrelationMember srt:MinimumMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:EquityContractMember us-gaap:DerivativeMember mfg:MeasurementInputEquityCorrelationMember srt:MaximumMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:EquityContractMember us-gaap:DerivativeMember mfg:MeasurementInputEquityVolatilityMember srt:MinimumMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:EquityContractMember us-gaap:DerivativeMember mfg:MeasurementInputEquityVolatilityMember srt:MaximumMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:EquityContractMember us-gaap:DerivativeMember mfg:MeasurementInputEquityIRCorrelationMember srt:WeightedAverageMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:EquityContractMember us-gaap:DerivativeMember mfg:MeasurementInputEquityFXCorrelationMember srt:WeightedAverageMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:EquityContractMember us-gaap:DerivativeMember mfg:MeasurementInputEquityCorrelationMember srt:WeightedAverageMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:EquityContractMember us-gaap:DerivativeMember mfg:MeasurementInputEquityVolatilityMember srt:WeightedAverageMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:CreditRiskContractMember us-gaap:DerivativeMember srt:MinimumMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:CreditRiskContractMember us-gaap:DerivativeMember srt:MaximumMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:CreditRiskContractMember us-gaap:DerivativeMember srt:WeightedAverageMember 2023-09-30 0001335730 mfg:InternalValuationModelMember mfg:OtherContractsMember us-gaap:DerivativeMember mfg:MeasurementInputCommodityVolatilityMember srt:MinimumMember 2023-09-30 0001335730 mfg:InternalValuationModelMember mfg:OtherContractsMember us-gaap:DerivativeMember mfg:MeasurementInputCommodityVolatilityMember srt:MaximumMember 2023-09-30 0001335730 mfg:InternalValuationModelMember mfg:OtherContractsMember us-gaap:DerivativeMember mfg:MeasurementInputCommodityVolatilityMember srt:WeightedAverageMember 2023-09-30 0001335730 us-gaap:CarryingReportedAmountFairValueDisclosureMember 2023-09-30 0001335730 us-gaap:EstimateOfFairValueFairValueDisclosureMember 2023-09-30 0001335730 us-gaap:FairValueInputsLevel1Member us-gaap:EstimateOfFairValueFairValueDisclosureMember 2023-09-30 0001335730 us-gaap:FairValueInputsLevel2Member us-gaap:EstimateOfFairValueFairValueDisclosureMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputIRIRCorrelationMember srt:MinimumMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputIRIRCorrelationMember srt:MaximumMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputFXIRCorrelationMember srt:MinimumMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputFXIRCorrelationMember srt:MaximumMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputFXFXCorrelationMember srt:MinimumMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputFXFXCorrelationMember srt:MaximumMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputEquityIRCorrelationMember srt:MinimumMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputEquityIRCorrelationMember srt:MaximumMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputEquityFXCorrelationMember srt:MinimumMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputEquityFXCorrelationMember srt:MaximumMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputEquityCorrelationMember srt:MinimumMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputEquityCorrelationMember srt:MaximumMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputEquityVolatilityMember srt:MinimumMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputEquityVolatilityMember srt:MaximumMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember us-gaap:MeasurementInputDefaultRateMember srt:MinimumMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember us-gaap:MeasurementInputDefaultRateMember srt:MaximumMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputIRIRCorrelationMember srt:WeightedAverageMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputFXIRCorrelationMember srt:WeightedAverageMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputFXFXCorrelationMember srt:WeightedAverageMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputEquityIRCorrelationMember srt:WeightedAverageMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputEquityFXCorrelationMember srt:WeightedAverageMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputEquityCorrelationMember srt:WeightedAverageMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputEquityVolatilityMember srt:WeightedAverageMember 2023-09-30 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember us-gaap:MeasurementInputDefaultRateMember srt:WeightedAverageMember 2023-09-30 0001335730 us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMember 2023-09-30 0001335730 mfg:TrustAccountsMember us-gaap:VariableInterestEntityPrimaryBeneficiaryMember 2023-09-30 0001335730 mfg:InvestmentsInSecuritizationProductsMember us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMember 2023-09-30 0001335730 mfg:AssetBackedSecuritizationsMember us-gaap:VariableInterestEntityPrimaryBeneficiaryMember 2023-09-30 0001335730 mfg:TrustAccountsMember us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMember 2023-09-30 0001335730 us-gaap:SecuritiesInvestmentMember us-gaap:VariableInterestEntityPrimaryBeneficiaryMember 2023-09-30 0001335730 mfg:AssetBackedSecuritizationsMember us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMember 2023-09-30 0001335730 us-gaap:AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember us-gaap:VariableInterestEntityPrimaryBeneficiaryMember 2023-09-30 0001335730 us-gaap:VariableInterestEntityPrimaryBeneficiaryMember 2023-09-30 0001335730 us-gaap:SecuritiesInvestmentMember us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMember 2023-09-30 0001335730 mfg:InvestmentsInSecuritizationProductsMember us-gaap:VariableInterestEntityPrimaryBeneficiaryMember 2023-09-30 0001335730 us-gaap:AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMember 2023-09-30 0001335730 srt:MaximumMember 2023-09-30 0001335730 srt:MinimumMember 2023-09-30 0001335730 srt:WeightedAverageMember 2023-09-30 0001335730 mfg:CommercialPaperAndCorporateBondsMember 2023-09-30 0001335730 mfg:EquitySecuritiesInSecuredBorrowingsMember 2023-09-30 0001335730 mfg:JapaneseGovernmentBondsLocalGovernmentBondsMember 2023-09-30 0001335730 mfg:OtherSecuritiesMember 2023-09-30 0001335730 mfg:ForeignGovernmentBondsAndForeignAgencyMortgageBackedSecuritiesMember 2023-09-30 0001335730 us-gaap:SeniorDebtObligationsMember 2023-09-30 0001335730 us-gaap:FairValueInputsLevel3Member us-gaap:EstimateOfFairValueFairValueDisclosureMember 2023-09-30 0001335730 us-gaap:InterestRateContractMember 2023-09-30 0001335730 us-gaap:CreditRiskContractMember 2023-09-30 0001335730 us-gaap:EquityContractMember 2023-09-30 0001335730 us-gaap:ForeignExchangeContractMember 2023-09-30 0001335730 us-gaap:OtherContractMember 2023-09-30 0001335730 mfg:TrustAccountsMember 2023-09-30 0001335730 us-gaap:SecuritiesInvestmentMember 2023-09-30 0001335730 us-gaap:AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember 2023-09-30 0001335730 mfg:AssetBackedSecuritizationsMember 2023-09-30 0001335730 mfg:InvestmentsInSecuritizationProductsMember 2023-09-30 0001335730 us-gaap:EquityContractMember us-gaap:NondesignatedMember 2023-09-30 0001335730 us-gaap:DesignatedAsHedgingInstrumentMember us-gaap:InterestRateContractMember 2023-09-30 0001335730 us-gaap:DesignatedAsHedgingInstrumentMember us-gaap:ForeignExchangeContractMember 2023-09-30 0001335730 us-gaap:DesignatedAsHedgingInstrumentMember us-gaap:EquityContractMember 2023-09-30 0001335730 us-gaap:DesignatedAsHedgingInstrumentMember us-gaap:CreditRiskContractMember 2023-09-30 0001335730 us-gaap:DesignatedAsHedgingInstrumentMember us-gaap:OtherContractMember 2023-09-30 0001335730 us-gaap:DesignatedAsHedgingInstrumentMember 2023-09-30 0001335730 us-gaap:CreditRiskContractMember us-gaap:NondesignatedMember 2023-09-30 0001335730 us-gaap:InterestRateContractMember us-gaap:NondesignatedMember 2023-09-30 0001335730 us-gaap:OtherContractMember us-gaap:NondesignatedMember 2023-09-30 0001335730 us-gaap:ForeignExchangeContractMember us-gaap:NondesignatedMember 2023-09-30 0001335730 us-gaap:NondesignatedMember 2023-09-30 0001335730 us-gaap:CommercialMortgageBackedSecuritiesMember us-gaap:DebtSecuritiesMember 2023-09-30 0001335730 mfg:ForeignGovernmentBondsMember us-gaap:DebtSecuritiesMember 2023-09-30 0001335730 mfg:GovernmentBondsMember us-gaap:DebtSecuritiesMember 2023-09-30 0001335730 us-gaap:DebtSecuritiesMember mfg:DomesticDebtSecuritiesMember 2023-09-30 0001335730 us-gaap:MortgageBackedSecuritiesOtherMember us-gaap:DebtSecuritiesMember 2023-09-30 0001335730 us-gaap:DebtSecuritiesMember us-gaap:MunicipalBondsMember 2023-09-30 0001335730 us-gaap:ForeignCorporateDebtSecuritiesMember us-gaap:DebtSecuritiesMember 2023-09-30 0001335730 us-gaap:ResidentialMortgageBackedSecuritiesMember us-gaap:DebtSecuritiesMember 2023-09-30 0001335730 us-gaap:DebtSecuritiesMember us-gaap:USTreasuryAndGovernmentShorttermDebtSecuritiesMember 2023-09-30 0001335730 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 mfg:GovernmentBondsMember us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 mfg:GovernmentBondsMember us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 mfg:GovernmentBondsMember us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 us-gaap:MunicipalBondsMember us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 us-gaap:MunicipalBondsMember us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 us-gaap:USTreasuryAndGovernmentShorttermDebtSecuritiesMember us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 us-gaap:USTreasuryAndGovernmentShorttermDebtSecuritiesMember us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 us-gaap:USTreasuryAndGovernmentShorttermDebtSecuritiesMember us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 mfg:ForeignGovernmentBondsMember us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 mfg:ForeignGovernmentBondsMember us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 mfg:ForeignGovernmentBondsMember us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 us-gaap:MortgageBackedSecuritiesOtherMember us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 us-gaap:MortgageBackedSecuritiesOtherMember us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 mfg:CertificatesOfDepositAndCommercialPaperMember us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 mfg:CertificatesOfDepositAndCommercialPaperMember us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 us-gaap:AllOtherCorporateBondsMember us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 us-gaap:AllOtherCorporateBondsMember us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 us-gaap:AllOtherCorporateBondsMember us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 us-gaap:EquitySecuritiesMember us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 us-gaap:EquitySecuritiesMember us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 us-gaap:EquitySecuritiesMember us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 us-gaap:EquitySecuritiesMember us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 us-gaap:InterestRateContractMember us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 us-gaap:InterestRateContractMember us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 us-gaap:InterestRateContractMember us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 us-gaap:InterestRateContractMember us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 us-gaap:ForeignExchangeContractMember us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 us-gaap:ForeignExchangeContractMember us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 us-gaap:ForeignExchangeContractMember us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 us-gaap:EquityContractMember us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 us-gaap:EquityContractMember us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 us-gaap:EquityContractMember us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 us-gaap:EquityContractMember us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 us-gaap:CreditRiskContractMember us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 us-gaap:CreditRiskContractMember us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 us-gaap:CreditRiskContractMember us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 us-gaap:OtherContractMember us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 us-gaap:OtherContractMember us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 us-gaap:OtherContractMember us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 us-gaap:OtherContractMember us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 us-gaap:ResidentialMortgageBackedSecuritiesMember us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 us-gaap:ResidentialMortgageBackedSecuritiesMember us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 us-gaap:ResidentialMortgageBackedSecuritiesMember us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 us-gaap:CommercialMortgageBackedSecuritiesMember us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 us-gaap:CommercialMortgageBackedSecuritiesMember us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 us-gaap:CommercialMortgageBackedSecuritiesMember us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 mfg:JapaneseCorporateBondsMember us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 mfg:JapaneseCorporateBondsMember us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 mfg:JapaneseCorporateBondsMember us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 mfg:NonJapaneseCorporateBondsMember us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 mfg:NonJapaneseCorporateBondsMember us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 mfg:NonJapaneseCorporateBondsMember us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember 2023-09-30 0001335730 mfg:DomesticDebtSecuritiesMember 2023-09-30 0001335730 mfg:GovernmentBondsMember us-gaap:HeldtomaturitySecuritiesMember 2023-09-30 0001335730 us-gaap:AccruedIncomeReceivableMember 2023-09-30 0001335730 mfg:FinancingReceivablesNotImpairedMember 2023-09-30 0001335730 us-gaap:SpecialMentionMember us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:OtherMember 2023-09-30 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionForeignMember mfg:SoverignMember us-gaap:SpecialMentionMember 2023-09-30 0001335730 mfg:NonAccrualLoansMember mfg:SmallAndMediumSizedCompaniesMember mfg:CorporateRatingMember us-gaap:GeographicDistributionDomesticMember mfg:FinancingReceivablesNotImpairedMember 2023-09-30 0001335730 us-gaap:SpecialMentionMember us-gaap:GeographicDistributionDomesticMember mfg:BanksAndFinancialInstitutionsMember 2023-09-30 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionForeignMember mfg:BanksAndFinancialInstitutionsMember mfg:NonAccrualLoansMember 2023-09-30 0001335730 us-gaap:SpecialMentionMember us-gaap:GeographicDistributionDomesticMember 2023-09-30 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionForeignMember mfg:RetailRatingMember us-gaap:PassMember 2023-09-30 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionForeignMember mfg:CorporateRatingMember us-gaap:PassMember 2023-09-30 0001335730 us-gaap:PassMember us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:FinancingReceivablesNotImpairedMember mfg:LargeCompaniesMember 2023-09-30 0001335730 us-gaap:PassMember us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:OtherMember 2023-09-30 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:SmallAndMediumSizedCompaniesMember us-gaap:PassMember 2023-09-30 0001335730 mfg:NonAccrualLoansMember us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:OtherMember 2023-09-30 0001335730 mfg:NonAccrualLoansMember mfg:CorporateRatingMember us-gaap:GeographicDistributionForeignMember mfg:FinancingReceivablesNotImpairedMember 2023-09-30 0001335730 us-gaap:PassMember mfg:BanksAndFinancialInstitutionsMember us-gaap:GeographicDistributionForeignMember mfg:FinancingReceivablesNotImpairedMember 2023-09-30 0001335730 mfg:NonAccrualLoansMember us-gaap:GeographicDistributionDomesticMember mfg:BanksAndFinancialInstitutionsMember 2023-09-30 0001335730 us-gaap:SpecialMentionMember mfg:SmallAndMediumSizedCompaniesMember mfg:CorporateRatingMember us-gaap:GeographicDistributionDomesticMember mfg:FinancingReceivablesNotImpairedMember 2023-09-30 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:SpecialMentionMember us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:LargeCompaniesMember 2023-09-30 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionForeignMember mfg:BanksAndFinancialInstitutionsMember us-gaap:SpecialMentionMember 2023-09-30 0001335730 us-gaap:PassMember us-gaap:GeographicDistributionDomesticMember 2023-09-30 0001335730 us-gaap:PassMember us-gaap:GeographicDistributionDomesticMember mfg:BanksAndFinancialInstitutionsMember 2023-09-30 0001335730 mfg:FinancingReceivablesNotImpairedMember mfg:NonAccrualLoansMember us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:LargeCompaniesMember 2023-09-30 0001335730 mfg:NonAccrualLoansMember us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:HousingLoanMember 2023-09-30 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionForeignMember mfg:SoverignMember us-gaap:PassMember 2023-09-30 0001335730 us-gaap:SpecialMentionMember us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:HousingLoanMember 2023-09-30 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionForeignMember mfg:RetailRatingMember mfg:NonAccrualLoansMember 2023-09-30 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionForeignMember mfg:CorporateRatingMember us-gaap:SpecialMentionMember 2023-09-30 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionForeignMember mfg:SoverignMember mfg:NonAccrualLoansMember 2023-09-30 0001335730 us-gaap:PassMember us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:HousingLoanMember 2023-09-30 0001335730 us-gaap:SpecialMentionMember mfg:RetailRatingMember us-gaap:GeographicDistributionForeignMember mfg:FinancingReceivablesNotImpairedMember 2023-09-30 0001335730 mfg:NonAccrualLoansMember us-gaap:GeographicDistributionDomesticMember 2023-09-30 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionForeignMember 2023-09-30 0001335730 mfg:SubjectToEnforceableMasterNettingArragementMember 2023-09-30 0001335730 mfg:NetOfAllowanceForCreditLossMember 2023-09-30 0001335730 us-gaap:AccruedIncomeReceivableMember mfg:AvailableForSaleAndHeldToMaturitySecuritiesMember 2023-09-30 0001335730 mfg:FinancingReceivablesImpairedMember 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:SmallAndMediumSizedCompaniesMember mfg:TotalPastDueMember 2023-09-30 0001335730 mfg:RetailRatingMember us-gaap:GeographicDistributionDomesticMember mfg:HousingLoanMember us-gaap:FinancingReceivables30To59DaysPastDueMember 2023-09-30 0001335730 mfg:HousingLoanMember mfg:RetailRatingMember us-gaap:GeographicDistributionDomesticMember mfg:TotalPastDueMember 2023-09-30 0001335730 us-gaap:FinancingReceivables30To59DaysPastDueMember mfg:OtherMember mfg:RetailRatingMember us-gaap:GeographicDistributionDomesticMember 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:OtherMember mfg:TotalPastDueMember 2023-09-30 0001335730 mfg:SoverignMember us-gaap:FinancingReceivables30To59DaysPastDueMember us-gaap:GeographicDistributionDomesticMember 2023-09-30 0001335730 mfg:SoverignMember mfg:TotalPastDueMember us-gaap:GeographicDistributionDomesticMember 2023-09-30 0001335730 mfg:BanksAndFinancialInstitutionsMember us-gaap:FinancingReceivables30To59DaysPastDueMember us-gaap:GeographicDistributionDomesticMember 2023-09-30 0001335730 mfg:TotalPastDueMember mfg:BanksAndFinancialInstitutionsMember us-gaap:GeographicDistributionDomesticMember 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember us-gaap:FinancingReceivables30To59DaysPastDueMember 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:TotalMember 2023-09-30 0001335730 us-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember us-gaap:GeographicDistributionForeignMember 2023-09-30 0001335730 mfg:CurrentMember us-gaap:GeographicDistributionDomesticMember 2023-09-30 0001335730 mfg:TotalMember 2023-09-30 0001335730 us-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember 2023-09-30 0001335730 mfg:TotalMember us-gaap:GeographicDistributionForeignMember 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:LargeCompaniesMember us-gaap:FinancingReceivables30To59DaysPastDueMember 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:HousingLoanMember mfg:CurrentMember 2023-09-30 0001335730 mfg:RetailRatingMember us-gaap:GeographicDistributionDomesticMember mfg:HousingLoanMember us-gaap:FinancingReceivables60To89DaysPastDueMember 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:SmallAndMediumSizedCompaniesMember mfg:CurrentMember 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:SmallAndMediumSizedCompaniesMember us-gaap:FinancingReceivables60To89DaysPastDueMember 2023-09-30 0001335730 mfg:LargeCompaniesMember mfg:CorporateRatingMember us-gaap:GeographicDistributionDomesticMember mfg:CurrentMember 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:LargeCompaniesMember us-gaap:FinancingReceivables60To89DaysPastDueMember 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:LargeCompaniesMember mfg:TotalPastDueMember 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:SmallAndMediumSizedCompaniesMember us-gaap:FinancingReceivables30To59DaysPastDueMember 2023-09-30 0001335730 mfg:TotalPastDueMember us-gaap:GeographicDistributionDomesticMember 2023-09-30 0001335730 mfg:CurrentMember 2023-09-30 0001335730 us-gaap:FinancingReceivables60To89DaysPastDueMember 2023-09-30 0001335730 mfg:CurrentMember us-gaap:GeographicDistributionForeignMember 2023-09-30 0001335730 us-gaap:FinancingReceivables60To89DaysPastDueMember us-gaap:GeographicDistributionForeignMember 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:TotalMember mfg:BanksAndFinancialInstitutionsMember 2023-09-30 0001335730 us-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember mfg:BanksAndFinancialInstitutionsMember us-gaap:GeographicDistributionDomesticMember 2023-09-30 0001335730 mfg:SoverignMember mfg:TotalMember us-gaap:GeographicDistributionDomesticMember 2023-09-30 0001335730 us-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember mfg:SoverignMember us-gaap:GeographicDistributionDomesticMember 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:OtherMember mfg:TotalMember 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember us-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember mfg:RetailRatingMember mfg:OtherMember 2023-09-30 0001335730 mfg:TotalMember mfg:HousingLoanMember mfg:RetailRatingMember us-gaap:GeographicDistributionDomesticMember 2023-09-30 0001335730 mfg:HousingLoanMember mfg:RetailRatingMember us-gaap:GeographicDistributionDomesticMember us-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:SmallAndMediumSizedCompaniesMember mfg:TotalMember 2023-09-30 0001335730 us-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember mfg:SmallAndMediumSizedCompaniesMember mfg:CorporateRatingMember us-gaap:GeographicDistributionDomesticMember 2023-09-30 0001335730 mfg:LargeCompaniesMember mfg:CorporateRatingMember us-gaap:GeographicDistributionDomesticMember mfg:TotalMember 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:LargeCompaniesMember us-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember 2023-09-30 0001335730 us-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember us-gaap:GeographicDistributionDomesticMember 2023-09-30 0001335730 mfg:TotalPastDueMember 2023-09-30 0001335730 us-gaap:FinancingReceivables30To59DaysPastDueMember 2023-09-30 0001335730 mfg:TotalPastDueMember us-gaap:GeographicDistributionForeignMember 2023-09-30 0001335730 us-gaap:FinancingReceivables30To59DaysPastDueMember us-gaap:GeographicDistributionForeignMember 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember us-gaap:FinancingReceivables60To89DaysPastDueMember 2023-09-30 0001335730 mfg:BanksAndFinancialInstitutionsMember mfg:CurrentMember us-gaap:GeographicDistributionDomesticMember 2023-09-30 0001335730 mfg:BanksAndFinancialInstitutionsMember us-gaap:FinancingReceivables60To89DaysPastDueMember us-gaap:GeographicDistributionDomesticMember 2023-09-30 0001335730 mfg:SoverignMember mfg:CurrentMember us-gaap:GeographicDistributionDomesticMember 2023-09-30 0001335730 mfg:SoverignMember us-gaap:FinancingReceivables60To89DaysPastDueMember us-gaap:GeographicDistributionDomesticMember 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:OtherMember mfg:CurrentMember 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:OtherMember us-gaap:FinancingReceivables60To89DaysPastDueMember 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:SmallAndMediumSizedCompaniesMember us-gaap:FinancialAssetPastDueMember mfg:CorporateRatingMember 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:SmallAndMediumSizedCompaniesMember us-gaap:FinancialAssetNotPastDueMember mfg:CorporateRatingMember 2023-09-30 0001335730 us-gaap:FinancialAssetPastDueMember mfg:RetailRatingMember mfg:HousingLoanMember us-gaap:GeographicDistributionDomesticMember 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:HousingLoanMember us-gaap:FinancialAssetNotPastDueMember mfg:RetailRatingMember 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:OtherMember us-gaap:FinancialAssetPastDueMember mfg:RetailRatingMember 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:OtherMember us-gaap:FinancialAssetNotPastDueMember mfg:RetailRatingMember 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember us-gaap:FinancingReceivables30To59DaysPastDueMember mfg:RetailRatingMember 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember us-gaap:FinancingReceivables60To89DaysPastDueMember mfg:RetailRatingMember 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember us-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember mfg:RetailRatingMember 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember us-gaap:FinancialAssetPastDueMember mfg:RetailRatingMember 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember us-gaap:FinancialAssetNotPastDueMember mfg:RetailRatingMember 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember 2023-09-30 0001335730 us-gaap:FinancialAssetPastDueMember us-gaap:GeographicDistributionForeignMember 2023-09-30 0001335730 us-gaap:FinancialAssetNotPastDueMember us-gaap:GeographicDistributionForeignMember 2023-09-30 0001335730 us-gaap:FinancialAssetPastDueMember 2023-09-30 0001335730 us-gaap:FinancialAssetNotPastDueMember 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:LargeCompaniesMember us-gaap:FinancialAssetNotPastDueMember mfg:CorporateRatingMember 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:LargeCompaniesMember us-gaap:FinancialAssetPastDueMember mfg:CorporateRatingMember 2023-09-30 0001335730 mfg:PerformanceFinancialMarketValueAndOtherTypeGuaranteeMember 2023-04-01 2023-09-30 0001335730 us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMember 2023-04-01 2023-09-30 0001335730 us-gaap:NondesignatedMember 2023-04-01 2023-09-30 0001335730 us-gaap:SecuritiesInvestmentMember 2023-04-01 2023-09-30 0001335730 mfg:DepositsRelatedBusinessMember 2023-04-01 2023-09-30 0001335730 us-gaap:FinancialServiceMember 2023-04-01 2023-09-30 0001335730 mfg:AgencyBusinessMember 2023-04-01 2023-09-30 0001335730 mfg:RemittanceBusinessMember 2023-04-01 2023-09-30 0001335730 mfg:SecuritiesRelatedBusinessMember 2023-04-01 2023-09-30 0001335730 us-gaap:FinancialServiceOtherMember 2023-04-01 2023-09-30 0001335730 us-gaap:FiduciaryAndTrustMember 2023-04-01 2023-09-30 0001335730 mfg:LendingRelatedBusinessMember 2023-04-01 2023-09-30 0001335730 mfg:GuaranteeRelatedBusinessMember 2023-04-01 2023-09-30 0001335730 us-gaap:InvestmentAdvisoryManagementAndAdministrativeServiceMember 2023-04-01 2023-09-30 0001335730 us-gaap:ForeignExchangeMember 2023-04-01 2023-09-30 0001335730 us-gaap:CreditRiskContractMember us-gaap:LoansMember 2023-04-01 2023-09-30 0001335730 us-gaap:ExchangeTradedFundsMember mfg:GlobalMarketsCompanyMember 2023-04-01 2023-09-30 0001335730 us-gaap:ExchangeTradedFundsMember 2023-04-01 2023-09-30 0001335730 us-gaap:LongTermDebtMember 2023-04-01 2023-09-30 0001335730 mfg:AccumulatedOwnCreditRiskAdjustmentMember mfg:OtherNoninterestIncomeExpensesMember 2023-04-01 2023-09-30 0001335730 us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMember mfg:SalaryAndBenefitMember 2023-04-01 2023-09-30 0001335730 us-gaap:AccumulatedNetUnrealizedInvestmentGainLossMember mfg:InvestmentGainsLossesNetAndOtherNoninterestIncomeMember 2023-04-01 2023-09-30 0001335730 mfg:TradingAccountGainsMember 2023-04-01 2023-09-30 0001335730 mfg:TradingSecuritiesMember 2023-04-01 2023-09-30 0001335730 us-gaap:AvailableforsaleSecuritiesMember 2023-04-01 2023-09-30 0001335730 us-gaap:ResidentialPortfolioSegmentMember us-gaap:GeographicDistributionDomesticMember 2023-04-01 2023-09-30 0001335730 us-gaap:GeographicDistributionForeignMember 2023-04-01 2023-09-30 0001335730 us-gaap:CommercialPortfolioSegmentMember us-gaap:GeographicDistributionDomesticMember 2023-04-01 2023-09-30 0001335730 mfg:BanksAndOtherFinancialInstitutionsMember us-gaap:GeographicDistributionDomesticMember 2023-04-01 2023-09-30 0001335730 mfg:SovereignMember us-gaap:GeographicDistributionDomesticMember 2023-04-01 2023-09-30 0001335730 us-gaap:DebtSecuritiesMember 2023-04-01 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:SmallAndMediumSizedCompaniesMember 2023-04-01 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:HousingLoanMember 2023-04-01 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:OtherMember 2023-04-01 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember 2023-04-01 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:LargeCompaniesMember 2023-04-01 2023-09-30 0001335730 us-gaap:EquitySecuritiesMember 2023-04-01 2023-09-30 0001335730 us-gaap:ForeignExchangeContractMember 2023-04-01 2023-09-30 0001335730 us-gaap:EquityContractMember 2023-04-01 2023-09-30 0001335730 us-gaap:CreditRiskContractMember 2023-04-01 2023-09-30 0001335730 us-gaap:InterestRateContractMember 2023-04-01 2023-09-30 0001335730 us-gaap:OtherContractMember 2023-04-01 2023-09-30 0001335730 us-gaap:SeniorDebtObligationsMember 2023-04-01 2023-09-30 0001335730 mfg:RetailAndBusinessBankingCompanyMember us-gaap:OperatingSegmentsMember 2023-04-01 2023-09-30 0001335730 mfg:GlobalMarketsCompanyMember us-gaap:OperatingSegmentsMember 2023-04-01 2023-09-30 0001335730 mfg:CorporateAndInstitutionalCompanyMember us-gaap:OperatingSegmentsMember 2023-04-01 2023-09-30 0001335730 mfg:AssetManagementCompanyMember us-gaap:OperatingSegmentsMember 2023-04-01 2023-09-30 0001335730 mfg:GlobalCorporateCompanyMember us-gaap:OperatingSegmentsMember 2023-04-01 2023-09-30 0001335730 us-gaap:IntersegmentEliminationMember 2023-04-01 2023-09-30 0001335730 us-gaap:AccumulatedForeignCurrencyAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember 2023-04-01 2023-09-30 0001335730 us-gaap:PropertyPlantAndEquipmentMember 2023-04-01 2023-09-30 0001335730 us-gaap:TreasuryStockCommonMember 2023-04-01 2023-09-30 0001335730 us-gaap:AccumulatedDefinedBenefitPlansAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember 2023-04-01 2023-09-30 0001335730 mfg:AccumulatedOwnCreditRiskAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember 2023-04-01 2023-09-30 0001335730 us-gaap:AccumulatedNetInvestmentGainLossIncludingPortionAttributableToNoncontrollingInterestMember 2023-04-01 2023-09-30 0001335730 us-gaap:CommonStockMember 2023-04-01 2023-09-30 0001335730 us-gaap:AccumulatedOtherComprehensiveIncomeMember 2023-04-01 2023-09-30 0001335730 us-gaap:RetainedEarningsMember 2023-04-01 2023-09-30 0001335730 us-gaap:AvailableforsaleSecuritiesMember us-gaap:OtherThanSecuritiesInvestmentMember 2023-04-01 2023-09-30 0001335730 us-gaap:DerivativeFinancialInstrumentsAssetsMember us-gaap:OtherContractMember 2023-04-01 2023-09-30 0001335730 us-gaap:DerivativeFinancialInstrumentsAssetsMember us-gaap:EquityContractMember 2023-04-01 2023-09-30 0001335730 us-gaap:DerivativeFinancialInstrumentsAssetsMember us-gaap:ForeignExchangeContractMember 2023-04-01 2023-09-30 0001335730 us-gaap:DerivativeFinancialInstrumentsAssetsMember us-gaap:InterestRateContractMember 2023-04-01 2023-09-30 0001335730 mfg:TradingSecuritiesMember us-gaap:EquitySecuritiesMember 2023-04-01 2023-09-30 0001335730 mfg:TradingSecuritiesMember us-gaap:AllOtherCorporateBondsMember 2023-04-01 2023-09-30 0001335730 us-gaap:NoncontrollingInterestMember 2023-04-01 2023-09-30 0001335730 us-gaap:AvailableforsaleSecuritiesMember mfg:JapaneseCorporateBondsMember 2023-04-01 2023-09-30 0001335730 us-gaap:AvailableforsaleSecuritiesMember mfg:NonJapaneseCorporateBondsMember 2023-04-01 2023-09-30 0001335730 us-gaap:AvailableforsaleSecuritiesMember us-gaap:CommercialMortgageBackedSecuritiesMember 2023-04-01 2023-09-30 0001335730 us-gaap:ResidentialMortgageBackedSecuritiesMember us-gaap:AvailableforsaleSecuritiesMember 2023-04-01 2023-09-30 0001335730 us-gaap:AccountingStandardsUpdate201409Member 2023-04-01 2023-09-30 0001335730 srt:MaximumMember 2023-04-01 2023-09-30 0001335730 us-gaap:InterestRateBelowMarketReductionMember 2023-04-01 2023-09-30 0001335730 us-gaap:ExtendedMaturityMember 2023-04-01 2023-09-30 0001335730 mfg:OtherLoanRestructuringModificationMember us-gaap:GeographicDistributionForeignMember 2023-04-01 2023-09-30 0001335730 us-gaap:PrincipalForgivenessMember us-gaap:GeographicDistributionForeignMember 2023-04-01 2023-09-30 0001335730 us-gaap:ExtendedMaturityAndInterestRateReductionMember us-gaap:GeographicDistributionForeignMember 2023-04-01 2023-09-30 0001335730 us-gaap:InterestRateBelowMarketReductionMember us-gaap:GeographicDistributionForeignMember 2023-04-01 2023-09-30 0001335730 us-gaap:ExtendedMaturityMember us-gaap:GeographicDistributionForeignMember 2023-04-01 2023-09-30 0001335730 mfg:OtherLoanRestructuringModificationMember us-gaap:GeographicDistributionDomesticMember 2023-04-01 2023-09-30 0001335730 us-gaap:PrincipalForgivenessMember us-gaap:GeographicDistributionDomesticMember 2023-04-01 2023-09-30 0001335730 us-gaap:ExtendedMaturityAndInterestRateReductionMember us-gaap:GeographicDistributionDomesticMember 2023-04-01 2023-09-30 0001335730 us-gaap:InterestRateBelowMarketReductionMember us-gaap:GeographicDistributionDomesticMember 2023-04-01 2023-09-30 0001335730 us-gaap:ExtendedMaturityMember us-gaap:GeographicDistributionDomesticMember 2023-04-01 2023-09-30 0001335730 mfg:OtherLoanRestructuringModificationMember us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:OtherMember 2023-04-01 2023-09-30 0001335730 us-gaap:PrincipalForgivenessMember us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:OtherMember 2023-04-01 2023-09-30 0001335730 us-gaap:ExtendedMaturityAndInterestRateReductionMember us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:OtherMember 2023-04-01 2023-09-30 0001335730 us-gaap:InterestRateBelowMarketReductionMember us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:OtherMember 2023-04-01 2023-09-30 0001335730 us-gaap:ExtendedMaturityMember us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:OtherMember 2023-04-01 2023-09-30 0001335730 mfg:OtherLoanRestructuringModificationMember us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:HousingLoanMember 2023-04-01 2023-09-30 0001335730 us-gaap:PrincipalForgivenessMember us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:HousingLoanMember 2023-04-01 2023-09-30 0001335730 us-gaap:ExtendedMaturityAndInterestRateReductionMember us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:HousingLoanMember 2023-04-01 2023-09-30 0001335730 us-gaap:InterestRateBelowMarketReductionMember us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:HousingLoanMember 2023-04-01 2023-09-30 0001335730 us-gaap:ExtendedMaturityMember us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:HousingLoanMember 2023-04-01 2023-09-30 0001335730 mfg:OtherLoanRestructuringModificationMember us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:SmallAndMediumSizedCompaniesMember 2023-04-01 2023-09-30 0001335730 us-gaap:PrincipalForgivenessMember us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:SmallAndMediumSizedCompaniesMember 2023-04-01 2023-09-30 0001335730 us-gaap:ExtendedMaturityAndInterestRateReductionMember us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:SmallAndMediumSizedCompaniesMember 2023-04-01 2023-09-30 0001335730 us-gaap:InterestRateBelowMarketReductionMember us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:SmallAndMediumSizedCompaniesMember 2023-04-01 2023-09-30 0001335730 us-gaap:ExtendedMaturityMember us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:SmallAndMediumSizedCompaniesMember 2023-04-01 2023-09-30 0001335730 mfg:OtherLoanRestructuringModificationMember us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:LargeCompaniesMember 2023-04-01 2023-09-30 0001335730 mfg:OtherLoanRestructuringModificationMember 2023-04-01 2023-09-30 0001335730 us-gaap:PrincipalForgivenessMember 2023-04-01 2023-09-30 0001335730 us-gaap:ExtendedMaturityAndInterestRateReductionMember 2023-04-01 2023-09-30 0001335730 us-gaap:ExtendedMaturityMember us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:LargeCompaniesMember 2023-04-01 2023-09-30 0001335730 us-gaap:InterestRateBelowMarketReductionMember us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:LargeCompaniesMember 2023-04-01 2023-09-30 0001335730 us-gaap:ExtendedMaturityAndInterestRateReductionMember us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:LargeCompaniesMember 2023-04-01 2023-09-30 0001335730 us-gaap:PrincipalForgivenessMember us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:LargeCompaniesMember 2023-04-01 2023-09-30 0001335730 mfg:PeriodEightMember mfg:BaselIiiMember 2023-04-01 2023-09-30 0001335730 mfg:SecuritiesRelatedBusinessMember 2022-04-01 2022-09-30 0001335730 us-gaap:FinancialServiceOtherMember 2022-04-01 2022-09-30 0001335730 us-gaap:FiduciaryAndTrustMember 2022-04-01 2022-09-30 0001335730 mfg:LendingRelatedBusinessMember 2022-04-01 2022-09-30 0001335730 mfg:GuaranteeRelatedBusinessMember 2022-04-01 2022-09-30 0001335730 us-gaap:InvestmentAdvisoryManagementAndAdministrativeServiceMember 2022-04-01 2022-09-30 0001335730 mfg:DepositsRelatedBusinessMember 2022-04-01 2022-09-30 0001335730 us-gaap:FinancialServiceMember 2022-04-01 2022-09-30 0001335730 mfg:AgencyBusinessMember 2022-04-01 2022-09-30 0001335730 mfg:RemittanceBusinessMember 2022-04-01 2022-09-30 0001335730 us-gaap:ForeignExchangeMember 2022-04-01 2022-09-30 0001335730 us-gaap:LoansMember us-gaap:CreditRiskContractMember 2022-04-01 2022-09-30 0001335730 mfg:TradingSecuritiesMember 2022-04-01 2022-09-30 0001335730 us-gaap:ExchangeTradedFundsMember 2022-04-01 2022-09-30 0001335730 us-gaap:ExchangeTradedFundsMember mfg:GlobalMarketsCompanyMember 2022-04-01 2022-09-30 0001335730 us-gaap:LongTermDebtMember 2022-04-01 2022-09-30 0001335730 mfg:CorporateRatingMember mfg:LargeCompaniesMember us-gaap:GeographicDistributionDomesticMember 2022-04-01 2022-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:SmallAndMediumSizedCompaniesMember mfg:CorporateRatingMember 2022-04-01 2022-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:HousingLoanMember mfg:RetailRatingMember 2022-04-01 2022-09-30 0001335730 mfg:RetailRatingMember mfg:OtherMember us-gaap:GeographicDistributionDomesticMember 2022-04-01 2022-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember 2022-04-01 2022-09-30 0001335730 us-gaap:GeographicDistributionForeignMember 2022-04-01 2022-09-30 0001335730 mfg:TradingAccountGainsMember 2022-04-01 2022-09-30 0001335730 us-gaap:AvailableforsaleSecuritiesMember 2022-04-01 2022-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember us-gaap:CommercialPortfolioSegmentMember 2022-04-01 2022-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember us-gaap:ResidentialPortfolioSegmentMember 2022-04-01 2022-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:SovereignMember 2022-04-01 2022-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:BanksAndOtherFinancialInstitutionsMember 2022-04-01 2022-09-30 0001335730 us-gaap:DebtSecuritiesMember 2022-04-01 2022-09-30 0001335730 us-gaap:EquitySecuritiesMember 2022-04-01 2022-09-30 0001335730 us-gaap:InterestRateContractMember 2022-04-01 2022-09-30 0001335730 us-gaap:OtherContractMember 2022-04-01 2022-09-30 0001335730 us-gaap:ForeignExchangeContractMember 2022-04-01 2022-09-30 0001335730 us-gaap:EquityContractMember 2022-04-01 2022-09-30 0001335730 us-gaap:CreditRiskContractMember 2022-04-01 2022-09-30 0001335730 us-gaap:SeniorDebtObligationsMember 2022-04-01 2022-09-30 0001335730 mfg:GlobalCorporateCompanyMember us-gaap:OperatingSegmentsMember 2022-04-01 2022-09-30 0001335730 us-gaap:IntersegmentEliminationMember 2022-04-01 2022-09-30 0001335730 mfg:RetailAndBusinessBankingCompanyMember us-gaap:OperatingSegmentsMember 2022-04-01 2022-09-30 0001335730 mfg:GlobalMarketsCompanyMember us-gaap:OperatingSegmentsMember 2022-04-01 2022-09-30 0001335730 mfg:AssetManagementCompanyMember us-gaap:OperatingSegmentsMember 2022-04-01 2022-09-30 0001335730 mfg:CorporateAndInstitutionalCompanyMember us-gaap:OperatingSegmentsMember 2022-04-01 2022-09-30 0001335730 us-gaap:AccumulatedForeignCurrencyAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember 2022-04-01 2022-09-30 0001335730 us-gaap:PropertyPlantAndEquipmentMember 2022-04-01 2022-09-30 0001335730 us-gaap:TreasuryStockCommonMember 2022-04-01 2022-09-30 0001335730 us-gaap:AccumulatedNetInvestmentGainLossIncludingPortionAttributableToNoncontrollingInterestMember 2022-04-01 2022-09-30 0001335730 us-gaap:AccumulatedDefinedBenefitPlansAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember 2022-04-01 2022-09-30 0001335730 mfg:AccumulatedOwnCreditRiskAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember 2022-04-01 2022-09-30 0001335730 us-gaap:CommonStockMember 2022-04-01 2022-09-30 0001335730 us-gaap:AccumulatedOtherComprehensiveIncomeMember 2022-04-01 2022-09-30 0001335730 us-gaap:RetainedEarningsMember 2022-04-01 2022-09-30 0001335730 us-gaap:OtherThanSecuritiesInvestmentMember us-gaap:AvailableforsaleSecuritiesMember 2022-04-01 2022-09-30 0001335730 mfg:TradingSecuritiesMember us-gaap:EquitySecuritiesMember 2022-04-01 2022-09-30 0001335730 us-gaap:DerivativeFinancialInstrumentsAssetsMember us-gaap:EquityContractMember 2022-04-01 2022-09-30 0001335730 us-gaap:ForeignExchangeContractMember us-gaap:DerivativeFinancialInstrumentsAssetsMember 2022-04-01 2022-09-30 0001335730 us-gaap:InterestRateContractMember us-gaap:DerivativeFinancialInstrumentsAssetsMember 2022-04-01 2022-09-30 0001335730 mfg:TradingSecuritiesMember us-gaap:AllOtherCorporateBondsMember 2022-04-01 2022-09-30 0001335730 mfg:CreditRelatedContractsMember us-gaap:DerivativeFinancialInstrumentsAssetsMember 2022-04-01 2022-09-30 0001335730 us-gaap:NoncontrollingInterestMember 2022-04-01 2022-09-30 0001335730 us-gaap:AvailableforsaleSecuritiesMember mfg:NonJapaneseCorporateBondsMember 2022-04-01 2022-09-30 0001335730 mfg:JapaneseCorporateBondsMember us-gaap:AvailableforsaleSecuritiesMember 2022-04-01 2022-09-30 0001335730 mfg:TradingSecuritiesMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2022-04-01 2022-09-30 0001335730 us-gaap:ResidentialMortgageBackedSecuritiesMember us-gaap:AvailableforsaleSecuritiesMember 2022-04-01 2022-09-30 0001335730 us-gaap:AccountingStandardsUpdate201409Member 2022-04-01 2022-09-30 0001335730 srt:MinimumMember 2022-04-01 2022-09-30 0001335730 mfg:DomesticDebtSecuritiesMember 2021-04-01 2022-03-31 0001335730 us-gaap:GeographicDistributionForeignMember 2022-04-01 2023-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:LargeCompaniesMember 2022-04-01 2023-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:OtherMember 2022-04-01 2023-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember 2022-04-01 2023-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:SmallAndMediumSizedCompaniesMember 2022-04-01 2023-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:HousingLoanMember 2022-04-01 2023-03-31 0001335730 mfg:PeriodEightMember mfg:BaselIiiMember 2022-04-01 2023-03-31 0001335730 mfg:GovernmentBondsMember us-gaap:HeldtomaturitySecuritiesMember 2022-03-31 0001335730 mfg:GovernmentBondsMember us-gaap:HeldtomaturitySecuritiesMember 2022-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember us-gaap:CommercialPortfolioSegmentMember 2023-03-31 0001335730 mfg:BanksAndOtherFinancialInstitutionsMember us-gaap:GeographicDistributionDomesticMember 2023-03-31 0001335730 mfg:SovereignMember us-gaap:GeographicDistributionDomesticMember 2023-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember us-gaap:ResidentialPortfolioSegmentMember 2023-03-31 0001335730 us-gaap:AccumulatedOtherComprehensiveIncomeMember 2023-03-31 0001335730 us-gaap:RetainedEarningsMember 2023-03-31 0001335730 us-gaap:TreasuryStockCommonMember 2023-03-31 0001335730 us-gaap:NoncontrollingInterestMember 2023-03-31 0001335730 us-gaap:CommonStockMember 2023-03-31 0001335730 us-gaap:AccumulatedDefinedBenefitPlansAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember 2023-03-31 0001335730 us-gaap:AccumulatedForeignCurrencyAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember 2023-03-31 0001335730 mfg:AccumulatedOwnCreditRiskAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember 2023-03-31 0001335730 us-gaap:AccumulatedNetInvestmentGainLossIncludingPortionAttributableToNoncontrollingInterestMember 2023-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember us-gaap:CommercialPortfolioSegmentMember 2023-09-30 0001335730 mfg:BanksAndOtherFinancialInstitutionsMember us-gaap:GeographicDistributionDomesticMember 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:SovereignMember 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember us-gaap:ResidentialPortfolioSegmentMember 2023-09-30 0001335730 us-gaap:AccumulatedForeignCurrencyAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember 2023-09-30 0001335730 mfg:AccumulatedOwnCreditRiskAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember 2023-09-30 0001335730 us-gaap:AccumulatedOtherComprehensiveIncomeMember 2023-09-30 0001335730 us-gaap:AccumulatedNetInvestmentGainLossIncludingPortionAttributableToNoncontrollingInterestMember 2023-09-30 0001335730 us-gaap:AccumulatedDefinedBenefitPlansAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember 2023-09-30 0001335730 mfg:TradingSecuritiesMember us-gaap:AllOtherCorporateBondsMember 2023-03-31 0001335730 mfg:TradingSecuritiesMember us-gaap:EquitySecuritiesMember 2023-03-31 0001335730 us-gaap:DerivativeFinancialInstrumentsAssetsMember us-gaap:InterestRateContractMember 2023-03-31 0001335730 us-gaap:DerivativeFinancialInstrumentsAssetsMember us-gaap:ForeignExchangeContractMember 2023-03-31 0001335730 us-gaap:DerivativeFinancialInstrumentsAssetsMember us-gaap:EquityContractMember 2023-03-31 0001335730 us-gaap:DerivativeFinancialInstrumentsAssetsMember mfg:CreditRelatedContractsMember 2023-03-31 0001335730 us-gaap:DerivativeFinancialInstrumentsAssetsMember us-gaap:OtherContractMember 2023-03-31 0001335730 us-gaap:AvailableforsaleSecuritiesMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2023-03-31 0001335730 us-gaap:AvailableforsaleSecuritiesMember mfg:NonJapaneseCorporateBondsMember 2023-03-31 0001335730 us-gaap:AvailableforsaleSecuritiesMember mfg:JapaneseCorporateBondsMember 2023-03-31 0001335730 us-gaap:AvailableforsaleSecuritiesMember us-gaap:OtherThanSecuritiesInvestmentMember 2023-03-31 0001335730 us-gaap:AvailableforsaleSecuritiesMember us-gaap:CommercialMortgageBackedSecuritiesMember 2023-09-30 0001335730 us-gaap:AvailableforsaleSecuritiesMember mfg:JapaneseCorporateBondsMember 2023-09-30 0001335730 us-gaap:AvailableforsaleSecuritiesMember mfg:NonJapaneseCorporateBondsMember 2023-09-30 0001335730 us-gaap:AvailableforsaleSecuritiesMember us-gaap:OtherThanSecuritiesInvestmentMember 2023-09-30 0001335730 us-gaap:AvailableforsaleSecuritiesMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2023-09-30 0001335730 mfg:TradingSecuritiesMember us-gaap:AllOtherCorporateBondsMember 2023-09-30 0001335730 us-gaap:DerivativeFinancialInstrumentsAssetsMember us-gaap:InterestRateContractMember 2023-09-30 0001335730 mfg:TradingSecuritiesMember us-gaap:EquitySecuritiesMember 2023-09-30 0001335730 us-gaap:DerivativeFinancialInstrumentsAssetsMember us-gaap:ForeignExchangeContractMember 2023-09-30 0001335730 us-gaap:DerivativeFinancialInstrumentsAssetsMember mfg:CreditRelatedContractsMember 2023-09-30 0001335730 us-gaap:DerivativeFinancialInstrumentsAssetsMember us-gaap:EquityContractMember 2023-09-30 0001335730 us-gaap:LongTermDebtMember 2023-03-31 0001335730 us-gaap:LongTermDebtMember 2023-09-30 0001335730 us-gaap:ParentMember 2023-09-30 0001335730 us-gaap:RetainedEarningsMember 2023-09-30 0001335730 us-gaap:CommonStockMember 2023-09-30 0001335730 us-gaap:TreasuryStockCommonMember 2023-09-30 0001335730 us-gaap:NoncontrollingInterestMember 2023-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember us-gaap:CommercialPortfolioSegmentMember 2022-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember us-gaap:ResidentialPortfolioSegmentMember 2022-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:SovereignMember 2022-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:BanksAndOtherFinancialInstitutionsMember 2022-03-31 0001335730 us-gaap:GeographicDistributionForeignMember 2022-03-31 0001335730 us-gaap:TreasuryStockCommonMember 2022-03-31 0001335730 us-gaap:NoncontrollingInterestMember 2022-03-31 0001335730 us-gaap:AccumulatedOtherComprehensiveIncomeMember 2022-03-31 0001335730 us-gaap:RetainedEarningsMember 2022-03-31 0001335730 us-gaap:CommonStockMember 2022-03-31 0001335730 us-gaap:AccumulatedForeignCurrencyAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember 2022-03-31 0001335730 mfg:AccumulatedOwnCreditRiskAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember 2022-03-31 0001335730 us-gaap:AccumulatedNetInvestmentGainLossIncludingPortionAttributableToNoncontrollingInterestMember 2022-03-31 0001335730 us-gaap:AccumulatedDefinedBenefitPlansAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember 2022-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:BanksAndOtherFinancialInstitutionsMember 2022-09-30 0001335730 us-gaap:GeographicDistributionForeignMember 2022-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:SovereignMember 2022-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember us-gaap:ResidentialPortfolioSegmentMember 2022-09-30 0001335730 us-gaap:GeographicDistributionDomesticMember us-gaap:CommercialPortfolioSegmentMember 2022-09-30 0001335730 us-gaap:AccumulatedNetInvestmentGainLossIncludingPortionAttributableToNoncontrollingInterestMember 2022-09-30 0001335730 us-gaap:AccumulatedDefinedBenefitPlansAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember 2022-09-30 0001335730 us-gaap:AccumulatedForeignCurrencyAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember 2022-09-30 0001335730 mfg:AccumulatedOwnCreditRiskAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember 2022-09-30 0001335730 us-gaap:AccumulatedOtherComprehensiveIncomeMember 2022-09-30 0001335730 mfg:CreditRelatedContractsMember us-gaap:DerivativeFinancialInstrumentsAssetsMember 2022-03-31 0001335730 us-gaap:OtherThanSecuritiesInvestmentMember us-gaap:AvailableforsaleSecuritiesMember 2022-03-31 0001335730 us-gaap:ResidentialMortgageBackedSecuritiesMember mfg:TradingSecuritiesMember 2022-03-31 0001335730 us-gaap:AllOtherCorporateBondsMember mfg:TradingSecuritiesMember 2022-03-31 0001335730 us-gaap:ForeignExchangeContractMember us-gaap:DerivativeFinancialInstrumentsAssetsMember 2022-03-31 0001335730 us-gaap:EquityContractMember us-gaap:DerivativeFinancialInstrumentsAssetsMember 2022-03-31 0001335730 us-gaap:ResidentialMortgageBackedSecuritiesMember us-gaap:AvailableforsaleSecuritiesMember 2022-03-31 0001335730 mfg:JapaneseCorporateBondsMember us-gaap:AvailableforsaleSecuritiesMember 2022-03-31 0001335730 mfg:NonJapaneseCorporateBondsMember us-gaap:AvailableforsaleSecuritiesMember 2022-03-31 0001335730 us-gaap:EquitySecuritiesMember mfg:TradingSecuritiesMember 2022-03-31 0001335730 us-gaap:InterestRateContractMember us-gaap:DerivativeFinancialInstrumentsAssetsMember 2022-03-31 0001335730 us-gaap:ForeignExchangeContractMember us-gaap:DerivativeFinancialInstrumentsAssetsMember 2022-09-30 0001335730 us-gaap:InterestRateContractMember us-gaap:DerivativeFinancialInstrumentsAssetsMember 2022-09-30 0001335730 us-gaap:EquityContractMember us-gaap:DerivativeFinancialInstrumentsAssetsMember 2022-09-30 0001335730 mfg:CreditRelatedContractsMember us-gaap:DerivativeFinancialInstrumentsAssetsMember 2022-09-30 0001335730 us-gaap:ResidentialMortgageBackedSecuritiesMember us-gaap:AvailableforsaleSecuritiesMember 2022-09-30 0001335730 us-gaap:AvailableforsaleSecuritiesMember mfg:JapaneseCorporateBondsMember 2022-09-30 0001335730 us-gaap:AvailableforsaleSecuritiesMember mfg:NonJapaneseCorporateBondsMember 2022-09-30 0001335730 us-gaap:ResidentialMortgageBackedSecuritiesMember mfg:TradingSecuritiesMember 2022-09-30 0001335730 us-gaap:AllOtherCorporateBondsMember mfg:TradingSecuritiesMember 2022-09-30 0001335730 us-gaap:EquitySecuritiesMember mfg:TradingSecuritiesMember 2022-09-30 0001335730 us-gaap:OtherThanSecuritiesInvestmentMember us-gaap:AvailableforsaleSecuritiesMember 2022-09-30 0001335730 us-gaap:LongTermDebtMember 2022-03-31 0001335730 us-gaap:LongTermDebtMember 2022-09-30 0001335730 us-gaap:TreasuryStockCommonMember 2022-09-30 0001335730 us-gaap:CommonStockMember 2022-09-30 0001335730 us-gaap:NoncontrollingInterestMember 2022-09-30 0001335730 us-gaap:ParentMember 2022-09-30 0001335730 us-gaap:RetainedEarningsMember 2022-09-30 iso4217:JPY xbrli:shares utr:Year xbrli:pure utr:Month mfg:Segment iso4217:JPY xbrli:shares