http://fasb.org/us-gaap/2021-01-31#OperatingLeaseLiabilityhttp://fasb.org/us-gaap/2021-01-31#OperatingLeaseLiabilityfalseFY0001335730--03-31U.S. GAAPhttp://fasb.org/us-gaap/2021-01-31#FinanceLeaseLiabilityhttp://fasb.org/us-gaap/2021-01-31#FinanceLeaseLiability2022-042022-042022-042022-042022-042022-062022-072022-042051-062048-032041-052081-092061-122041-092031-09These amounts resulted from the adoption of ASU No.2017-12, “Derivatives and Hedging (Topic 815)—Targeted Improvements to Accounting for Hedging Activities.”These amounts resulted from the adoption of ASU No.2016-13, “Financial Instruments—Credit Losses (Topic 326)—Measurement of Credit Losses on Financial Instruments” and subsequent amendments. See Note 1 “Basis of presentation and summary of significant accounting policies” for further details.The amounts that have been reclassified out of Accumulated other comprehensive income (loss), net of tax into net income are presented in Note 16 “Accumulated other comprehensive income (loss), net of tax.”Amortized cost, net of the allowance for credit losses, of which the amounts related to available-for-sale securities were ¥13,617 million at March 31, 2021, and ¥34,326 million at March 31, 2022.Accrued interest receivables are excluded from amortized cost, of which the amount were ¥10,379 million at March 31, 2021, and ¥4,702 million at March 31, 2022 and included in Accrued income.Agency mortgage-backed securities presented in this line consist of Japanese and Foreign agency mortgage-backed securities, of which the fair values were ¥520,746 million and ¥33 million, respectively, at March 31, 2021, and ¥450,507 million and ¥33 million, respectively, at March 31, 2022. 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.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 ¥275,661 million at March 31, 2021, and ¥247,762 million at March 31, 2022.All Agency mortgage-backed securities presented in this line are Ginnie Mae securities.Agency mortgage-backed securities presented in this line consist of Japanese agency mortgage-backed securities, of which the fair values were ¥107,077 million at March 31, 2021, and ¥261,867 million at March 31, 2022. All Japanese agency mortgage-backed securities are issued by Japan Housing Finance Agency, a Japanese government-sponsored enterprise.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 24 “Variable interest entities and securitizations” for further discussion of the guaranteed principal money trusts.The MHFG Group adopted ASU No.2017-12, “Derivatives and Hedging (Topic 815)—Targeted Improvements to Accounting for Hedging Activities” (“ASU No.2017-12”) on April 1, 2019 and the ASU No.2017-12 eliminated the separate measurement and reporting of hedge ineffectiveness. Cumulative-effect adjustment to the consolidated balance sheets was recognized upon adoption.The financial statement line item in which the amounts in the before tax column are reported in the consolidated statements of income is listed to the right of the table.The financial statement line items in which the amounts in the tax effect and the net of tax attributable to noncontrolling interest columns are reported in the consolidated statements of income are Income tax expense and Net income, respectively.The required ratios disclosed above, at March 31, 2021 and 2022, include the capital conservation buffer of 2.5%, the countercyclical capital buffer of 0.01% and the additional loss absorbency requirements for G-SIBs and 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.For the fiscal years ended March 31, 2020, 2021 and 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 fiscal year ended March 31, 2022, the computation of diluted earnings per common share did not assume exercise of stock options, as the effect of such exercise would be anti-dilutive due to net loss.Notional amount includes the sum of gross long and gross short third-party contracts.Derivative receivables and payables are recorded in Trading account assets and Trading account liabilities, respectively.The net gains (losses) excluded from the assessment of the effectiveness of fair value hedges is not included in the above table.Amounts include the net gains (losses) of ¥2,838 million, ¥(2,956) million and ¥(605) million on the credit derivatives economically managing the credit risk of loans during the fiscal years ended March 31, 2020, 2021 and 2022, respectively.Investment grade in the internal rating scale generally corresponds to BBB- or above in the external rating scale.Commitments to extend credit include commitments to invest in securities.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 are revenues from contracts within the scope of ASC 606, “Revenue from contracts with customers” (“ASC 606”).These amounts are revenues from contracts that do not meet the scope of 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.These amounts include the net unrealized gains resulting from changes in fair values of structured notes that contain embedded derivatives. See Note 27 “Fair value” for further details.Trading securities include foreign currency denominated securities for which the MHFG Group elected the fair value option.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, 2021 and 2022 were ¥55 billion and ¥68 billion, respectively.Amounts represent items for which the Group elected the fair value option or for which it applied the practicability exception.Total Level 3 derivative exposures have been netted on the table for presentation purposes only.Gains (losses) in Earnings are reported in Trading account gains (losses)—net, Foreign exchange gains (losses)—net or Other noninterest income (expenses).Gains (losses) in Earnings are reported in Investment gains (losses)—net.Gains (losses) in OCI are reported in Other comprehensive income (loss).Amounts represent total gains or losses recognized in earnings and OCI 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 March 31, 2021 and 2022. The amounts of unrealized gains (losses) in OCI related to Available-for-sale securities and Long-term debt, which were ¥6 billion and ¥(17) billion, respectively, at March 31, 2021, and ¥0 billion and ¥0 billion, respectively, at March 31, 2022.Gains (losses) in Earnings are reported in Other noninterest income (expenses).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.These inputs are mainly used for determining the fair values of securitization products such as CDO, CLO and ABS, other than RMBS and CMBS.This input is mainly used for determining the fair values of Japanese corporate bonds and foreign corporate bonds.Internal valuation model includes discounted cash flow models and the Black-Scholes option pricing model.Loans, net of allowance include items measured at fair value on a nonrecurring basis. 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.Derivative assets and liabilities are recorded in Trading account assets and Trading account liabilities, respectively.The amounts of derivative assets and liabilities subject to enforceable master netting arrangements or similar agreements were ¥8,168 billion and ¥7,652 billion, respectively, at March 31, 2021, and ¥9,326 billion and ¥9,235 billion, respectively, at March 31, 2022.Amounts do not exceed the net amounts presented on the balance sheet and do not include the effect of overcollateralization, where it exists.For derivatives, amounts include derivative assets or liabilities and securities collateral that are eligible for offsetting under enforceable master netting arrangements or similar agreements.The amounts of Receivables under resale agreements and Payables under repurchase agreements subject to enforceable industry standard master repurchase agreements with netting terms were ¥10,551 billion and ¥18,321 billion, respectively, at March 31, 2021, and ¥11,537 billion and ¥19,505 billion respectively, at March 31, 2022.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 ¥2,694 billion and ¥958 billion, respectively, at March 31, 2021, and ¥2,339 billion and ¥1,172 billion respectively, at March 31, 2022.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.The required and actual amounts disclosed above at March 31, 2021 and March 31, 2022 exclude amounts of deposits to the Bank of Japan.Right-of-use assets and lease liabilities are included in Other assets and Other liabilities, respectively, on the consolidated balance sheets.Lease cost for operating leases are included in Occupancy expenses on the consolidated statements of income. The Group’s variable lease costs and costs for leases with terms of twelve months or less are not significant.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.“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 fiscal years ended March 31, 2020, 2021 and 2022,net gains (losses) related to ETFs and others amounted to ¥10.6 billion, ¥2.0 billion and ¥1.9 billion, respectively, of which ¥7.3 billion, ¥(1.3) billion and ¥2.3 billion are included in “Global Markets Company,” respectively.“General and administrative expenses” excludes non-allocated gains (losses), net.“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 and others. Measurement of net business profits (losses) is required for regulatory reporting to the Financial Services Agency of Japan.“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.The MHFG Group adopted ASU No.2016-13, 2019-04, 2019-05, and 2019-11 on April 1, 2020. Allowances for credit losses for the fiscal year ended March 31, 2021 substitute allowances for loan losses and off-balance-sheet instruments for the fiscal years ended March 31, 2020. 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.Customer relationships were acquired in connection with the merger of MHSC and Shinko on May 7, 2009 and the integration among asset management companies on October 1, 2016. See Note 1 “Basis of presentation and summary of significant accounting policies” for further information.These amounts for the fiscal year ended March 31, 2022 represent mainly the reversal of an outside basis difference related to the share buyback conducted by MHSC in response to improving the capital position and aligning to the MHFG Group’s capital policy and the related increase in the valuation allowance.This figure includes 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 amount includes ¥85,001 million and ¥0 million related to MHSC’s net operating loss carryforwards resulting mainly from the organizational restructuring of certain foreign subsidiaries as of March 31, 2021 and 2022, respectively. The tax effect of the net operating loss carryforwards is substantially offset by ¥56,928 million and ¥0 million, respectively, of valuation allowance as a result of considering all available evidence regarding sources of future taxable income including historical trends in taxable income in the preceding periods and forecasted taxable income.The amount includes ¥0 million related to MHFG’s net operating loss carryforwards resulting mainly from intercompany capital transactions in relation to the share buyback conducted by MHSC as of March 31, 2022. The tax effect of the net operating loss carryforwards is substantially offset by ¥0 million of valuation allowance as a result of considering all available evidence regarding sources of future taxable income including historical trends in taxable income in the preceding periods and forecasted taxable income.The amounts of commercial paper and short-term notes issued by MHFG’s subsidiaries were ¥2,105,068million and ¥423,500 million, respectively, at March 31, 2021, and ¥1,775,860 million and ¥490,500 million, respectively, at March 31, 2022.Short-term notes are issued under the laws of Japan in the form of commercial paper.The United Kingdom net operating loss carryforwards may be carried forward indefinitely for tax purposes.Including the net operating loss carryforwards which may be carried forward indefinitely in the United Kingdom.The plans with projected benefit obligations in excess of plan assets include those with accumulated benefit obligations in excess of plan assets.The amount of ¥74,160 million for March 31, 2021 includes ¥73,998 million of prior service benefits recognized during the six months ended September 30, 2020 related to an amendment to the defined benefit pension plans at MHFG and certain domestic subsidiaries. In September 2020, based on various approvals, MHFG and certain domestic subsidiaries communicated to their employees the amendment to the defined benefit pension plans that was effective as of October 1, 2020. In accordance with ASC 715, “Compensation—Retirement Benefits” (“ASC 715”), any change in projected benefit obligations due to a plan amendment is required to be recognized as prior service benefits (cost) as of the amendment date.During the fiscal year ended March 31, 2021 and 2022, certain subsidiaries of MHFG partially withdrew assets from employee retirement benefit trusts, which were established for the payment of employees’ severance pay and retirement pensions. Overall, the trusts remain in overfunded status as of March 31, 2022. No gains or losses have been recognized as a result of this transaction.General account of life insurance companies is a contract with life insurance companies which guarantees payments of principal and predetermined interest payments.This class represents equity securities held in the employee retirement benefit trusts of ¥1,291 billion and ¥0 billion carried at fair value at March 31, 2021 and 2022, respectively, which are well-diversified across industries.These classes primarily include pension investment fund trusts. Investments in these classes are generally measured at fair value and can be redeemed within a short-term period upon request.¥85 billion of the Japan deferred tax assets of ¥94 billion is related to MHSC, which is substantially offset by a valuation allowance, and will expire during the fiscal year ending March 31, 2026.¥74 billion of the Japan deferred tax assets of ¥106 billion is related to MHSC, which is substantially offset by a valuation allowance, and will expire during the fiscal year ending March 31, 2026. ¥27 billion of the Japan deferred tax assets of ¥106 billion is related to MHFG, which is substantially offset by a valuation allowance, and will mostly expire during the fiscal year ending March 31, 2032. Investments in this class are measured at conversion value, which is equivalent to fair value.Amounts primarily include cash and short-term assets carried at fair value.In accordance with ASC 820, certain plan assets 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.Amounts include gains and losses on currency swaps.Amounts do not include the net gains (losses) of ¥2,838 million, ¥(2,956) million and ¥(605) million on the credit derivatives economically managing the credit risk of loans during the fiscal years ended March 31, 2020, 2021 and 2022, respectively. The net gains (losses) is recorded in Other noninterest income (expenses).Amounts include realized and unrealized gains and losses on both derivative instruments and nonderivative instruments. Amounts on derivative instruments include gains and losses on forward foreign exchange contracts and currency options. Amounts on nonderivative instruments include translation gains and losses related to foreign currency-denominated debt securities reported as Trading securities.Total expenses are comprised of Interest expense, Provision (credit) for credit losses and Noninterest expenses. Total revenue is comprised of Interest and dividend income and Noninterest income.The interest rates disclosed reflect the range of contractual rates in effect at March 31, 2022.Maturity information disclosed is the range of maturities at March 31, 2022.Figures assume that the countercyclical capital buffer will continue to be 0.01% after March 2023.Figures assume that the additional loss absorbency requirements applied to the Group as a G-SIB and D-SIB continue to be 1.0% on a fully effective basis in future years.The amount of ¥21,632 million and ¥23,845 million of settlement for March 31, 2021 resulted from partial transition from the defined benefit pension plans to the defined contribution pension plans, which occurred during the second half of the fiscal year ended March 31, 2021 at MHFG and certain domestic subsidiaries. This partial transition constitutes a settlement under ASC 715 and any gain or loss is required to be recognized in the consolidated results of operations once settlement criteria are met. The settlement criteria were met during the second half of the fiscal year ended March 31, 2021. 0001335730 2021-03-31 0001335730 2022-03-31 0001335730 2019-04-01 2020-03-31 0001335730 2020-04-01 2021-03-31 0001335730 2021-04-01 2022-03-31 0001335730 2020-03-31 0001335730 2019-03-31 0001335730 2018-04-01 2019-03-31 0001335730 2020-09-30 0001335730 mfg:ClassSixteenPreferredStockMember 2021-03-31 0001335730 mfg:ClassFifteenPreferredStockMember 2021-03-31 0001335730 mfg:ClassFourteenPreferredStockMember 2021-03-31 0001335730 us-gaap:MortgageBackedSecuritiesOtherMember mfg:DomesticGovernmentSponsoredEnterprisesDebtSecuritiesMember us-gaap:DebtSecuritiesMember 2021-03-31 0001335730 us-gaap:MortgageBackedSecuritiesOtherMember us-gaap:DebtSecuritiesMember 2021-03-31 0001335730 mfg:ForeignGovernmentBondsMember us-gaap:DebtSecuritiesMember 2021-03-31 0001335730 us-gaap:DebtSecuritiesMember us-gaap:USTreasuryAndGovernmentShorttermDebtSecuritiesMember 2021-03-31 0001335730 us-gaap:MunicipalBondsMember us-gaap:DebtSecuritiesMember 2021-03-31 0001335730 mfg:GovernmentBondsMember us-gaap:DebtSecuritiesMember 2021-03-31 0001335730 us-gaap:ForeignCorporateDebtSecuritiesMember us-gaap:DebtSecuritiesMember 2021-03-31 0001335730 mfg:DomesticDebtSecuritiesMember us-gaap:DebtSecuritiesMember 2021-03-31 0001335730 us-gaap:CommercialMortgageBackedSecuritiesMember us-gaap:DebtSecuritiesMember 2021-03-31 0001335730 us-gaap:ResidentialMortgageBackedSecuritiesMember us-gaap:DebtSecuritiesMember 2021-03-31 0001335730 mfg:GovernmentBondsMember us-gaap:DebtSecuritiesMember us-gaap:AvailableforsaleSecuritiesMember 2021-03-31 0001335730 us-gaap:MunicipalBondsMember us-gaap:DebtSecuritiesMember us-gaap:AvailableforsaleSecuritiesMember 2021-03-31 0001335730 mfg:ForeignGovernmentBondsMember us-gaap:DebtSecuritiesMember us-gaap:AvailableforsaleSecuritiesMember 2021-03-31 0001335730 us-gaap:MortgageBackedSecuritiesOtherMember us-gaap:DebtSecuritiesMember us-gaap:AvailableforsaleSecuritiesMember 2021-03-31 0001335730 us-gaap:ResidentialMortgageBackedSecuritiesMember us-gaap:DebtSecuritiesMember us-gaap:AvailableforsaleSecuritiesMember 2021-03-31 0001335730 us-gaap:CommercialMortgageBackedSecuritiesMember us-gaap:DebtSecuritiesMember us-gaap:AvailableforsaleSecuritiesMember 2021-03-31 0001335730 mfg:DomesticDebtSecuritiesMember us-gaap:DebtSecuritiesMember us-gaap:AvailableforsaleSecuritiesMember 2021-03-31 0001335730 us-gaap:DebtSecuritiesMember us-gaap:ForeignCorporateDebtSecuritiesMember us-gaap:AvailableforsaleSecuritiesMember 2021-03-31 0001335730 us-gaap:AvailableforsaleSecuritiesMember us-gaap:DebtSecuritiesMember 2021-03-31 0001335730 us-gaap:USTreasuryAndGovernmentShorttermDebtSecuritiesMember us-gaap:DebtSecuritiesMember us-gaap:AvailableforsaleSecuritiesMember 2021-03-31 0001335730 us-gaap:DebtSecuritiesMember mfg:ForeignAgencyMortgageBackedSecuritiesMember us-gaap:MortgageBackedSecuritiesOtherMember 2021-03-31 0001335730 us-gaap:DebtSecuritiesMember mfg:NegotiableCertificatesOfDepositsAssetBackedSecuritiesAndCollateralLoanObligationsMember 2021-03-31 0001335730 mfg:MizuhoFinancialGroupInc.Member 2021-03-31 0001335730 us-gaap:PerformanceGuaranteeMember 2021-03-31 0001335730 us-gaap:PerformanceGuaranteeMember mfg:ExpirationPeriodOneYearOrLessMember 2021-03-31 0001335730 us-gaap:PerformanceGuaranteeMember mfg:ExpirationPeriodAfterOneYearThroughFiveYearsMember 2021-03-31 0001335730 us-gaap:PerformanceGuaranteeMember mfg:ExpirationPeriodAfterFiveYearsMember 2021-03-31 0001335730 us-gaap:FinancialGuaranteeMember 2021-03-31 0001335730 us-gaap:FinancialGuaranteeMember mfg:ExpirationPeriodOneYearOrLessMember 2021-03-31 0001335730 us-gaap:FinancialGuaranteeMember mfg:ExpirationPeriodAfterOneYearThroughFiveYearsMember 2021-03-31 0001335730 us-gaap:FinancialGuaranteeMember mfg:ExpirationPeriodAfterFiveYearsMember 2021-03-31 0001335730 us-gaap:MarketValueGuaranteeMember 2021-03-31 0001335730 us-gaap:MarketValueGuaranteeMember mfg:ExpirationPeriodOneYearOrLessMember 2021-03-31 0001335730 us-gaap:MarketValueGuaranteeMember mfg:ExpirationPeriodAfterOneYearThroughFiveYearsMember 2021-03-31 0001335730 us-gaap:GuaranteeTypeOtherMember 2021-03-31 0001335730 us-gaap:GuaranteeTypeOtherMember mfg:ExpirationPeriodOneYearOrLessMember 2021-03-31 0001335730 us-gaap:GuaranteeTypeOtherMember mfg:ExpirationPeriodAfterOneYearThroughFiveYearsMember 2021-03-31 0001335730 us-gaap:GuaranteeTypeOtherMember mfg:ExpirationPeriodAfterFiveYearsMember 2021-03-31 0001335730 mfg:GuaranteesForRepaymentOfTrustPrincipalMember 2021-03-31 0001335730 mfg:ExpirationPeriodOneYearOrLessMember mfg:GuaranteesForRepaymentOfTrustPrincipalMember 2021-03-31 0001335730 mfg:GuaranteesForRepaymentOfTrustPrincipalMember mfg:ExpirationPeriodAfterOneYearThroughFiveYearsMember 2021-03-31 0001335730 mfg:GuaranteesForRepaymentOfTrustPrincipalMember mfg:ExpirationPeriodAfterFiveYearsMember 2021-03-31 0001335730 mfg:GuaranteesOnTrustAccountsMember 2021-03-31 0001335730 mfg:GuaranteesOnTrustAccountsMember mfg:ExpirationPeriodOneYearOrLessMember 2021-03-31 0001335730 mfg:GuaranteesOnTrustAccountsMember mfg:ExpirationPeriodAfterOneYearThroughFiveYearsMember 2021-03-31 0001335730 mfg:GuaranteesOnTrustAccountsMember mfg:ExpirationPeriodAfterFiveYearsMember 2021-03-31 0001335730 us-gaap:PaymentGuaranteeMember 2021-03-31 0001335730 us-gaap:PaymentGuaranteeMember mfg:ExpirationPeriodOneYearOrLessMember 2021-03-31 0001335730 us-gaap:PaymentGuaranteeMember mfg:ExpirationPeriodAfterOneYearThroughFiveYearsMember 2021-03-31 0001335730 us-gaap:PaymentGuaranteeMember mfg:ExpirationPeriodAfterFiveYearsMember 2021-03-31 0001335730 mfg:ExpirationPeriodAfterFiveYearsMember us-gaap:MarketValueGuaranteeMember 2021-03-31 0001335730 mfg:ExpirationPeriodOneYearOrLessMember 2021-03-31 0001335730 mfg:ExpirationPeriodAfterOneYearThroughFiveYearsMember 2021-03-31 0001335730 mfg:ExpirationPeriodAfterFiveYearsMember 2021-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember 2021-03-31 0001335730 mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2021-03-31 0001335730 mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:CommercialMortgageBackedSecuritiesMember 2021-03-31 0001335730 mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:AllOtherCorporateBondsMember 2021-03-31 0001335730 mfg:DebtInstrumentMember 2021-03-31 0001335730 mfg:MaturityOvernightAndOpenMember 2021-03-31 0001335730 us-gaap:MaturityUpTo30DaysMember 2021-03-31 0001335730 mfg:Maturity31To90DaysMember 2021-03-31 0001335730 us-gaap:MaturityOver90DaysMember 2021-03-31 0001335730 mfg:ImpairedFinancingReceivablesWithNoRelatedAllowanceMember 2021-03-31 0001335730 mfg:MarketableEquitySecuritiesMember 2021-03-31 0001335730 mfg:SecuritizationsMember 2021-03-31 0001335730 mfg:LoanParticipationsMember 2021-03-31 0001335730 us-gaap:DerivativeMember us-gaap:InterestRateContractMember 2021-03-31 0001335730 us-gaap:DerivativeMember us-gaap:ForeignExchangeContractMember 2021-03-31 0001335730 us-gaap:DerivativeMember us-gaap:EquityContractMember 2021-03-31 0001335730 us-gaap:DerivativeMember us-gaap:CreditRiskContractMember 2021-03-31 0001335730 mfg:MizuhoFinancialGroupIncMember mfg:JapanGaapConsolidatedMember 2021-03-31 0001335730 mfg:MizuhoBankLimitedMember mfg:JapanGaapConsolidatedMember 2021-03-31 0001335730 mfg:JapanGaapUnconsolidatedAffiliatesMember mfg:MizuhoBankLimitedMember 2021-03-31 0001335730 mfg:MizuhoTrustBankingCompanyLimitedMember mfg:JapanGaapUnconsolidatedAffiliatesMember 2021-03-31 0001335730 mfg:JapanGaapConsolidatedMember mfg:MizuhoTrustBankingCompanyLimitedMember 2021-03-31 0001335730 mfg:CreditRiskContractWrittenMember us-gaap:ExternalCreditRatingInvestmentGradeMember 2021-03-31 0001335730 mfg:CreditRiskContractWrittenMember us-gaap:ExternalCreditRatingNonInvestmentGradeMember 2021-03-31 0001335730 mfg:CreditRiskContractWrittenMember 2021-03-31 0001335730 mfg:CreditRiskContractPurchasedMember 2021-03-31 0001335730 us-gaap:RiskLevelLowMember mfg:PerformanceFinancialMarketValueAndOtherTypeGuaranteeMember 2021-03-31 0001335730 us-gaap:RiskLevelHighMember mfg:PerformanceFinancialMarketValueAndOtherTypeGuaranteeMember 2021-03-31 0001335730 mfg:PerformanceFinancialMarketValueAndOtherTypeGuaranteeMember 2021-03-31 0001335730 us-gaap:CommitmentsToExtendCreditMember 2021-03-31 0001335730 us-gaap:UnusedLinesOfCreditMember 2021-03-31 0001335730 us-gaap:LongTermDebtMember 2021-03-31 0001335730 us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMember mfg:MizuhoFinancialGroupIncMember 2021-03-31 0001335730 us-gaap:FairValueMeasurementsNonrecurringMember 2021-03-31 0001335730 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsNonrecurringMember 2021-03-31 0001335730 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsNonrecurringMember 2021-03-31 0001335730 us-gaap:PortionAtOtherThanFairValueFairValueDisclosureMember us-gaap:FairValueMeasurementsNonrecurringMember 2021-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:HousingLoanMember 2021-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:OtherMember 2021-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember 2021-03-31 0001335730 us-gaap:GeographicDistributionForeignMember 2021-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:LargeCompaniesMember 2021-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:SmallAndMediumSizedCompaniesMember mfg:CorporateRatingMember 2021-03-31 0001335730 mfg:AvailableForSaleAndTradingSecuritiesMember mfg:DiscountedCashFlowsValuationTechniqueMember us-gaap:MeasurementInputPrepaymentRateMember srt:MinimumMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2021-03-31 0001335730 mfg:AvailableForSaleAndTradingSecuritiesMember mfg:DiscountedCashFlowsValuationTechniqueMember us-gaap:MeasurementInputPrepaymentRateMember srt:MaximumMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2021-03-31 0001335730 mfg:AvailableForSaleAndTradingSecuritiesMember mfg:DiscountedCashFlowsValuationTechniqueMember us-gaap:MeasurementInputDefaultRateMember srt:MinimumMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2021-03-31 0001335730 mfg:AvailableForSaleAndTradingSecuritiesMember mfg:DiscountedCashFlowsValuationTechniqueMember us-gaap:MeasurementInputDefaultRateMember srt:MaximumMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2021-03-31 0001335730 mfg:AvailableForSaleAndTradingSecuritiesMember mfg:DiscountedCashFlowsValuationTechniqueMember mfg:MeasurementInputRecoveryRateMember srt:MinimumMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2021-03-31 0001335730 mfg:AvailableForSaleAndTradingSecuritiesMember mfg:DiscountedCashFlowsValuationTechniqueMember mfg:MeasurementInputRecoveryRateMember srt:MaximumMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2021-03-31 0001335730 mfg:AvailableForSaleAndTradingSecuritiesMember mfg:DiscountedCashFlowsValuationTechniqueMember us-gaap:MeasurementInputDiscountRateMember srt:MinimumMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2021-03-31 0001335730 mfg:AvailableForSaleAndTradingSecuritiesMember mfg:DiscountedCashFlowsValuationTechniqueMember us-gaap:MeasurementInputDiscountRateMember srt:MaximumMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2021-03-31 0001335730 mfg:AvailableForSaleAndTradingSecuritiesMember mfg:DiscountedCashFlowsValuationTechniqueMember mfg:MeasurementInputDiscountRate1Member srt:MinimumMember us-gaap:CommercialMortgageBackedSecuritiesMember 2021-03-31 0001335730 mfg:AvailableForSaleAndTradingSecuritiesMember mfg:DiscountedCashFlowsValuationTechniqueMember mfg:MeasurementInputDiscountRate1Member srt:MaximumMember us-gaap:CommercialMortgageBackedSecuritiesMember 2021-03-31 0001335730 mfg:AvailableForSaleAndTradingSecuritiesMember mfg:DiscountedCashFlowsValuationTechniqueMember srt:WeightedAverageMember us-gaap:MeasurementInputPrepaymentRateMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2021-03-31 0001335730 mfg:AvailableForSaleAndTradingSecuritiesMember mfg:DiscountedCashFlowsValuationTechniqueMember us-gaap:ResidentialMortgageBackedSecuritiesMember srt:WeightedAverageMember us-gaap:MeasurementInputDefaultRateMember 2021-03-31 0001335730 mfg:AvailableForSaleAndTradingSecuritiesMember mfg:DiscountedCashFlowsValuationTechniqueMember us-gaap:ResidentialMortgageBackedSecuritiesMember mfg:MeasurementInputRecoveryRateMember srt:WeightedAverageMember 2021-03-31 0001335730 mfg:AvailableForSaleAndTradingSecuritiesMember mfg:DiscountedCashFlowsValuationTechniqueMember us-gaap:ResidentialMortgageBackedSecuritiesMember us-gaap:MeasurementInputDiscountRateMember srt:WeightedAverageMember 2021-03-31 0001335730 mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:CommercialMortgageBackedSecuritiesMember mfg:DiscountedCashFlowsValuationTechniqueMember mfg:MeasurementInputDiscountRate1Member srt:WeightedAverageMember 2021-03-31 0001335730 us-gaap:AllOtherCorporateBondsMember mfg:AvailableForSaleAndTradingSecuritiesMember srt:MinimumMember mfg:DiscountedCashFlowsValuationTechniqueMember us-gaap:MeasurementInputPrepaymentRateMember 2021-03-31 0001335730 us-gaap:AllOtherCorporateBondsMember mfg:AvailableForSaleAndTradingSecuritiesMember srt:MaximumMember mfg:DiscountedCashFlowsValuationTechniqueMember us-gaap:MeasurementInputPrepaymentRateMember 2021-03-31 0001335730 us-gaap:AllOtherCorporateBondsMember mfg:AvailableForSaleAndTradingSecuritiesMember srt:MinimumMember us-gaap:MeasurementInputDefaultRateMember mfg:DiscountedCashFlowsValuationTechniqueMember 2021-03-31 0001335730 us-gaap:AllOtherCorporateBondsMember mfg:AvailableForSaleAndTradingSecuritiesMember srt:MaximumMember us-gaap:MeasurementInputDefaultRateMember mfg:DiscountedCashFlowsValuationTechniqueMember 2021-03-31 0001335730 us-gaap:AllOtherCorporateBondsMember mfg:AvailableForSaleAndTradingSecuritiesMember srt:MinimumMember mfg:DiscountedCashFlowsValuationTechniqueMember mfg:MeasurementInputRecoveryRateMember 2021-03-31 0001335730 us-gaap:AllOtherCorporateBondsMember mfg:AvailableForSaleAndTradingSecuritiesMember srt:MaximumMember mfg:DiscountedCashFlowsValuationTechniqueMember mfg:MeasurementInputRecoveryRateMember 2021-03-31 0001335730 us-gaap:AllOtherCorporateBondsMember mfg:AvailableForSaleAndTradingSecuritiesMember srt:MinimumMember us-gaap:MeasurementInputDiscountRateMember mfg:DiscountedCashFlowsValuationTechniqueMember 2021-03-31 0001335730 us-gaap:AllOtherCorporateBondsMember mfg:AvailableForSaleAndTradingSecuritiesMember srt:MaximumMember us-gaap:MeasurementInputDiscountRateMember mfg:DiscountedCashFlowsValuationTechniqueMember 2021-03-31 0001335730 us-gaap:AllOtherCorporateBondsMember mfg:AvailableForSaleAndTradingSecuritiesMember srt:MinimumMember mfg:DiscountedCashFlowsValuationTechniqueMember mfg:MeasurementInputDiscountRate1Member 2021-03-31 0001335730 us-gaap:AllOtherCorporateBondsMember mfg:AvailableForSaleAndTradingSecuritiesMember srt:MaximumMember mfg:DiscountedCashFlowsValuationTechniqueMember mfg:MeasurementInputDiscountRate1Member 2021-03-31 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember us-gaap:AllOtherCorporateBondsMember srt:WeightedAverageMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:MeasurementInputPrepaymentRateMember 2021-03-31 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember us-gaap:AllOtherCorporateBondsMember srt:WeightedAverageMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:MeasurementInputDefaultRateMember 2021-03-31 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember us-gaap:AllOtherCorporateBondsMember srt:WeightedAverageMember mfg:AvailableForSaleAndTradingSecuritiesMember mfg:MeasurementInputRecoveryRateMember 2021-03-31 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember us-gaap:AllOtherCorporateBondsMember srt:WeightedAverageMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:MeasurementInputDiscountRateMember 2021-03-31 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember us-gaap:AllOtherCorporateBondsMember srt:WeightedAverageMember mfg:AvailableForSaleAndTradingSecuritiesMember mfg:MeasurementInputDiscountRate1Member 2021-03-31 0001335730 us-gaap:HeldtomaturitySecuritiesMember us-gaap:DebtSecuritiesMember 2021-03-31 0001335730 us-gaap:MortgageBackedSecuritiesOtherMember us-gaap:DebtSecuritiesMember us-gaap:HeldtomaturitySecuritiesMember 2021-03-31 0001335730 mfg:GovernmentBondsMember us-gaap:DebtSecuritiesMember us-gaap:HeldtomaturitySecuritiesMember 2021-03-31 0001335730 us-gaap:ForeignExchangeContractMember us-gaap:DerivativeMember mfg:InternalValuationModelMember srt:MaximumMember mfg:MeasurementInputFXIRCorrelationMember 2021-03-31 0001335730 us-gaap:ForeignExchangeContractMember us-gaap:DerivativeMember mfg:InternalValuationModelMember srt:MinimumMember mfg:MeasurementInputFXFXCorrelationMember 2021-03-31 0001335730 us-gaap:ForeignExchangeContractMember us-gaap:DerivativeMember mfg:InternalValuationModelMember srt:MaximumMember mfg:MeasurementInputFXFXCorrelationMember 2021-03-31 0001335730 us-gaap:DerivativeMember us-gaap:EquityContractMember srt:MinimumMember mfg:MeasurementInputEquityIRCorrelationMember mfg:InternalValuationModelMember 2021-03-31 0001335730 us-gaap:DerivativeMember us-gaap:EquityContractMember srt:MaximumMember mfg:MeasurementInputEquityIRCorrelationMember mfg:InternalValuationModelMember 2021-03-31 0001335730 us-gaap:DerivativeMember us-gaap:EquityContractMember srt:MinimumMember mfg:MeasurementInputEquityCorrelationMember mfg:InternalValuationModelMember 2021-03-31 0001335730 us-gaap:DerivativeMember us-gaap:EquityContractMember srt:MaximumMember mfg:MeasurementInputEquityCorrelationMember mfg:InternalValuationModelMember 2021-03-31 0001335730 us-gaap:DerivativeMember us-gaap:EquityContractMember srt:MinimumMember mfg:MeasurementInputEquityVolatilityMember mfg:InternalValuationModelMember 2021-03-31 0001335730 us-gaap:DerivativeMember us-gaap:EquityContractMember srt:MaximumMember mfg:MeasurementInputEquityVolatilityMember mfg:InternalValuationModelMember 2021-03-31 0001335730 srt:WeightedAverageMember mfg:MeasurementInputFXIRCorrelationMember us-gaap:ForeignExchangeContractMember us-gaap:DerivativeMember mfg:InternalValuationModelMember 2021-03-31 0001335730 srt:WeightedAverageMember mfg:MeasurementInputFXFXCorrelationMember us-gaap:ForeignExchangeContractMember us-gaap:DerivativeMember mfg:InternalValuationModelMember 2021-03-31 0001335730 mfg:InternalValuationModelMember srt:WeightedAverageMember us-gaap:DerivativeMember us-gaap:EquityContractMember mfg:MeasurementInputEquityIRCorrelationMember 2021-03-31 0001335730 mfg:InternalValuationModelMember srt:WeightedAverageMember us-gaap:DerivativeMember us-gaap:EquityContractMember mfg:MeasurementInputEquityCorrelationMember 2021-03-31 0001335730 mfg:InternalValuationModelMember srt:WeightedAverageMember us-gaap:DerivativeMember us-gaap:EquityContractMember mfg:MeasurementInputEquityVolatilityMember 2021-03-31 0001335730 us-gaap:CreditRiskContractMember mfg:InternalValuationModelMember us-gaap:DerivativeMember srt:MinimumMember us-gaap:MeasurementInputDefaultRateMember 2021-03-31 0001335730 us-gaap:CreditRiskContractMember mfg:InternalValuationModelMember us-gaap:DerivativeMember srt:MaximumMember us-gaap:MeasurementInputDefaultRateMember 2021-03-31 0001335730 us-gaap:CreditRiskContractMember mfg:InternalValuationModelMember us-gaap:DerivativeMember srt:MinimumMember mfg:MeasurementInputCreditCorrelationMember 2021-03-31 0001335730 us-gaap:CreditRiskContractMember mfg:InternalValuationModelMember us-gaap:DerivativeMember srt:MaximumMember mfg:MeasurementInputCreditCorrelationMember 2021-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:CreditRiskContractMember srt:WeightedAverageMember us-gaap:DerivativeMember us-gaap:MeasurementInputDefaultRateMember 2021-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:CreditRiskContractMember srt:WeightedAverageMember us-gaap:DerivativeMember mfg:MeasurementInputCreditCorrelationMember 2021-03-31 0001335730 srt:MinimumMember us-gaap:DerivativeMember mfg:MeasurementInputCommodityVolatilityMember mfg:InternalValuationModelMember mfg:OtherContractsMember 2021-03-31 0001335730 srt:MaximumMember us-gaap:DerivativeMember mfg:MeasurementInputCommodityVolatilityMember mfg:InternalValuationModelMember mfg:OtherContractsMember 2021-03-31 0001335730 srt:WeightedAverageMember us-gaap:DerivativeMember mfg:MeasurementInputCommodityVolatilityMember mfg:InternalValuationModelMember mfg:OtherContractsMember 2021-03-31 0001335730 us-gaap:DerivativeMember us-gaap:InterestRateContractMember mfg:InternalValuationModelMember srt:MinimumMember mfg:MeasurementInputIRIRCorrelationMember 2021-03-31 0001335730 us-gaap:DerivativeMember us-gaap:InterestRateContractMember mfg:InternalValuationModelMember srt:MaximumMember mfg:MeasurementInputIRIRCorrelationMember 2021-03-31 0001335730 srt:WeightedAverageMember mfg:MeasurementInputIRIRCorrelationMember us-gaap:DerivativeMember us-gaap:InterestRateContractMember mfg:InternalValuationModelMember 2021-03-31 0001335730 us-gaap:ForeignExchangeContractMember us-gaap:DerivativeMember mfg:InternalValuationModelMember srt:MinimumMember mfg:MeasurementInputFXIRCorrelationMember 2021-03-31 0001335730 us-gaap:LongTermDebtMember mfg:InternalValuationModelMember srt:MinimumMember mfg:MeasurementInputIRIRCorrelationMember 2021-03-31 0001335730 us-gaap:LongTermDebtMember mfg:InternalValuationModelMember srt:MaximumMember mfg:MeasurementInputIRIRCorrelationMember 2021-03-31 0001335730 us-gaap:LongTermDebtMember mfg:InternalValuationModelMember srt:MinimumMember mfg:MeasurementInputFXIRCorrelationMember 2021-03-31 0001335730 us-gaap:LongTermDebtMember mfg:InternalValuationModelMember srt:MaximumMember mfg:MeasurementInputFXIRCorrelationMember 2021-03-31 0001335730 us-gaap:LongTermDebtMember mfg:InternalValuationModelMember srt:MinimumMember mfg:MeasurementInputFXFXCorrelationMember 2021-03-31 0001335730 us-gaap:LongTermDebtMember mfg:InternalValuationModelMember srt:MaximumMember mfg:MeasurementInputFXFXCorrelationMember 2021-03-31 0001335730 us-gaap:LongTermDebtMember mfg:InternalValuationModelMember srt:MinimumMember mfg:MeasurementInputEquityIRCorrelationMember 2021-03-31 0001335730 us-gaap:LongTermDebtMember mfg:InternalValuationModelMember srt:MaximumMember mfg:MeasurementInputEquityIRCorrelationMember 2021-03-31 0001335730 us-gaap:LongTermDebtMember mfg:InternalValuationModelMember srt:MinimumMember mfg:MeasurementInputEquityFXCorrelationMember 2021-03-31 0001335730 us-gaap:LongTermDebtMember mfg:InternalValuationModelMember srt:MaximumMember mfg:MeasurementInputEquityFXCorrelationMember 2021-03-31 0001335730 us-gaap:LongTermDebtMember mfg:InternalValuationModelMember srt:MinimumMember mfg:MeasurementInputEquityCorrelationMember 2021-03-31 0001335730 us-gaap:LongTermDebtMember mfg:InternalValuationModelMember srt:MaximumMember mfg:MeasurementInputEquityCorrelationMember 2021-03-31 0001335730 us-gaap:LongTermDebtMember mfg:InternalValuationModelMember srt:MinimumMember mfg:MeasurementInputEquityVolatilityMember 2021-03-31 0001335730 us-gaap:LongTermDebtMember mfg:InternalValuationModelMember srt:MaximumMember mfg:MeasurementInputEquityVolatilityMember 2021-03-31 0001335730 us-gaap:LongTermDebtMember mfg:InternalValuationModelMember srt:MinimumMember us-gaap:MeasurementInputDefaultRateMember 2021-03-31 0001335730 us-gaap:LongTermDebtMember mfg:InternalValuationModelMember srt:MaximumMember us-gaap:MeasurementInputDefaultRateMember 2021-03-31 0001335730 mfg:MeasurementInputCreditCorrelationMember srt:MinimumMember mfg:InternalValuationModelMember us-gaap:LongTermDebtMember 2021-03-31 0001335730 us-gaap:LongTermDebtMember mfg:InternalValuationModelMember srt:MaximumMember mfg:MeasurementInputCreditCorrelationMember 2021-03-31 0001335730 us-gaap:LongTermDebtMember srt:WeightedAverageMember mfg:InternalValuationModelMember mfg:MeasurementInputIRIRCorrelationMember 2021-03-31 0001335730 us-gaap:LongTermDebtMember srt:WeightedAverageMember mfg:InternalValuationModelMember mfg:MeasurementInputFXIRCorrelationMember 2021-03-31 0001335730 us-gaap:LongTermDebtMember srt:WeightedAverageMember mfg:InternalValuationModelMember mfg:MeasurementInputFXFXCorrelationMember 2021-03-31 0001335730 us-gaap:LongTermDebtMember srt:WeightedAverageMember mfg:InternalValuationModelMember mfg:MeasurementInputEquityIRCorrelationMember 2021-03-31 0001335730 us-gaap:LongTermDebtMember srt:WeightedAverageMember mfg:InternalValuationModelMember mfg:MeasurementInputEquityFXCorrelationMember 2021-03-31 0001335730 us-gaap:LongTermDebtMember srt:WeightedAverageMember mfg:InternalValuationModelMember mfg:MeasurementInputEquityCorrelationMember 2021-03-31 0001335730 us-gaap:LongTermDebtMember srt:WeightedAverageMember mfg:InternalValuationModelMember mfg:MeasurementInputEquityVolatilityMember 2021-03-31 0001335730 us-gaap:LongTermDebtMember srt:WeightedAverageMember mfg:InternalValuationModelMember us-gaap:MeasurementInputDefaultRateMember 2021-03-31 0001335730 us-gaap:LongTermDebtMember srt:WeightedAverageMember mfg:InternalValuationModelMember mfg:MeasurementInputCreditCorrelationMember 2021-03-31 0001335730 mfg:JapaneseGovernmentBondsLocalGovernmentBondsMember 2021-03-31 0001335730 mfg:ForeignGovernmentBondsAndForeignAgencyMortgageBackedSecuritiesMember 2021-03-31 0001335730 mfg:CommercialPaperAndCorporateBondsMember 2021-03-31 0001335730 mfg:EquitySecuritiesInSecuredBorrowingsMember 2021-03-31 0001335730 mfg:OtherSecuritiesMember 2021-03-31 0001335730 us-gaap:CarryingReportedAmountFairValueDisclosureMember 2021-03-31 0001335730 us-gaap:EstimateOfFairValueFairValueDisclosureMember 2021-03-31 0001335730 us-gaap:EstimateOfFairValueFairValueDisclosureMember us-gaap:FairValueInputsLevel1Member 2021-03-31 0001335730 us-gaap:EstimateOfFairValueFairValueDisclosureMember us-gaap:FairValueInputsLevel2Member 2021-03-31 0001335730 us-gaap:AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember us-gaap:VariableInterestEntityPrimaryBeneficiaryMember 2021-03-31 0001335730 mfg:AssetBackedSecuritizationsMember us-gaap:VariableInterestEntityPrimaryBeneficiaryMember 2021-03-31 0001335730 mfg:AssetBackedSecuritizationsMember us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMember 2021-03-31 0001335730 mfg:InvestmentsInSecuritizationProductsMember us-gaap:VariableInterestEntityPrimaryBeneficiaryMember 2021-03-31 0001335730 us-gaap:SecuritiesInvestmentMember us-gaap:VariableInterestEntityPrimaryBeneficiaryMember 2021-03-31 0001335730 us-gaap:SecuritiesInvestmentMember us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMember 2021-03-31 0001335730 mfg:TrustAccountsMember us-gaap:VariableInterestEntityPrimaryBeneficiaryMember 2021-03-31 0001335730 us-gaap:VariableInterestEntityPrimaryBeneficiaryMember 2021-03-31 0001335730 us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMember 2021-03-31 0001335730 us-gaap:SeniorDebtObligationsMember 2021-03-31 0001335730 us-gaap:EstimateOfFairValueFairValueDisclosureMember us-gaap:FairValueInputsLevel3Member 2021-03-31 0001335730 us-gaap:InterestRateContractMember 2021-03-31 0001335730 us-gaap:ForeignExchangeContractMember 2021-03-31 0001335730 us-gaap:EquityContractMember 2021-03-31 0001335730 us-gaap:CreditRiskContractMember 2021-03-31 0001335730 us-gaap:OtherContractMember 2021-03-31 0001335730 mfg:AssetBackedSecuritizationsMember 2021-03-31 0001335730 us-gaap:SecuritiesInvestmentMember 2021-03-31 0001335730 us-gaap:InterestRateContractMember us-gaap:NondesignatedMember 2021-03-31 0001335730 us-gaap:ForeignExchangeContractMember us-gaap:NondesignatedMember 2021-03-31 0001335730 us-gaap:EquityContractMember us-gaap:NondesignatedMember 2021-03-31 0001335730 us-gaap:CreditRiskContractMember us-gaap:NondesignatedMember 2021-03-31 0001335730 us-gaap:OtherContractMember us-gaap:NondesignatedMember 2021-03-31 0001335730 us-gaap:NondesignatedMember 2021-03-31 0001335730 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember 2021-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:FairValueInputsLevel2Member 2021-03-31 0001335730 us-gaap:FairValueInputsLevel1Member mfg:GovernmentBondsMember us-gaap:FairValueMeasurementsRecurringMember 2021-03-31 0001335730 us-gaap:FairValueInputsLevel2Member mfg:GovernmentBondsMember us-gaap:FairValueMeasurementsRecurringMember 2021-03-31 0001335730 mfg:GovernmentBondsMember us-gaap:FairValueMeasurementsRecurringMember 2021-03-31 0001335730 us-gaap:FairValueInputsLevel2Member us-gaap:MunicipalBondsMember us-gaap:FairValueMeasurementsRecurringMember 2021-03-31 0001335730 us-gaap:MunicipalBondsMember us-gaap:FairValueMeasurementsRecurringMember 2021-03-31 0001335730 us-gaap:FairValueInputsLevel1Member us-gaap:USTreasuryAndGovernmentShorttermDebtSecuritiesMember us-gaap:FairValueMeasurementsRecurringMember 2021-03-31 0001335730 us-gaap:FairValueInputsLevel2Member us-gaap:USTreasuryAndGovernmentShorttermDebtSecuritiesMember us-gaap:FairValueMeasurementsRecurringMember 2021-03-31 0001335730 us-gaap:USTreasuryAndGovernmentShorttermDebtSecuritiesMember us-gaap:FairValueMeasurementsRecurringMember 2021-03-31 0001335730 us-gaap:FairValueInputsLevel1Member mfg:ForeignGovernmentBondsMember us-gaap:FairValueMeasurementsRecurringMember 2021-03-31 0001335730 us-gaap:FairValueInputsLevel2Member mfg:ForeignGovernmentBondsMember us-gaap:FairValueMeasurementsRecurringMember 2021-03-31 0001335730 mfg:ForeignGovernmentBondsMember us-gaap:FairValueMeasurementsRecurringMember 2021-03-31 0001335730 us-gaap:FairValueInputsLevel2Member us-gaap:MortgageBackedSecuritiesOtherMember us-gaap:FairValueMeasurementsRecurringMember 2021-03-31 0001335730 us-gaap:MortgageBackedSecuritiesOtherMember us-gaap:FairValueMeasurementsRecurringMember 2021-03-31 0001335730 us-gaap:FairValueInputsLevel3Member us-gaap:ResidentialMortgageBackedSecuritiesMember us-gaap:FairValueMeasurementsRecurringMember 2021-03-31 0001335730 us-gaap:ResidentialMortgageBackedSecuritiesMember us-gaap:FairValueMeasurementsRecurringMember 2021-03-31 0001335730 us-gaap:FairValueInputsLevel2Member mfg:CertificatesOfDepositAndCommercialPaperMember us-gaap:FairValueMeasurementsRecurringMember 2021-03-31 0001335730 mfg:CertificatesOfDepositAndCommercialPaperMember us-gaap:FairValueMeasurementsRecurringMember 2021-03-31 0001335730 us-gaap:FairValueInputsLevel1Member us-gaap:AllOtherCorporateBondsMember us-gaap:FairValueMeasurementsRecurringMember 2021-03-31 0001335730 us-gaap:FairValueInputsLevel2Member us-gaap:AllOtherCorporateBondsMember us-gaap:FairValueMeasurementsRecurringMember 2021-03-31 0001335730 us-gaap:FairValueInputsLevel3Member us-gaap:AllOtherCorporateBondsMember us-gaap:FairValueMeasurementsRecurringMember 2021-03-31 0001335730 us-gaap:AllOtherCorporateBondsMember us-gaap:FairValueMeasurementsRecurringMember 2021-03-31 0001335730 us-gaap:FairValueInputsLevel1Member us-gaap:EquitySecuritiesMember us-gaap:FairValueMeasurementsRecurringMember 2021-03-31 0001335730 us-gaap:FairValueInputsLevel2Member us-gaap:EquitySecuritiesMember us-gaap:FairValueMeasurementsRecurringMember 2021-03-31 0001335730 us-gaap:FairValueInputsLevel3Member us-gaap:EquitySecuritiesMember us-gaap:FairValueMeasurementsRecurringMember 2021-03-31 0001335730 us-gaap:EquitySecuritiesMember us-gaap:FairValueMeasurementsRecurringMember 2021-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:InterestRateContractMember us-gaap:FairValueInputsLevel1Member 2021-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:FairValueInputsLevel2Member us-gaap:InterestRateContractMember 2021-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:InterestRateContractMember us-gaap:FairValueInputsLevel3Member 2021-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:InterestRateContractMember 2021-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:ForeignExchangeContractMember us-gaap:FairValueInputsLevel2Member 2021-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:ForeignExchangeContractMember us-gaap:FairValueInputsLevel3Member 2021-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:ForeignExchangeContractMember 2021-03-31 0001335730 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:EquityContractMember 2021-03-31 0001335730 us-gaap:EquityContractMember us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember 2021-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:FairValueInputsLevel3Member us-gaap:EquityContractMember 2021-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:EquityContractMember 2021-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:FairValueInputsLevel2Member us-gaap:CreditRiskContractMember 2021-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:FairValueInputsLevel3Member us-gaap:CreditRiskContractMember 2021-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:CreditRiskContractMember 2021-03-31 0001335730 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:OtherContractMember 2021-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:FairValueInputsLevel2Member us-gaap:OtherContractMember 2021-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:FairValueInputsLevel3Member us-gaap:OtherContractMember 2021-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:OtherContractMember 2021-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:FairValueInputsLevel2Member us-gaap:ResidentialMortgageBackedSecuritiesMember 2021-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:FairValueInputsLevel3Member us-gaap:CommercialMortgageBackedSecuritiesMember 2021-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:CommercialMortgageBackedSecuritiesMember 2021-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:FairValueInputsLevel2Member mfg:JapaneseCorporateBondsMember 2021-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:FairValueInputsLevel3Member mfg:JapaneseCorporateBondsMember 2021-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember mfg:JapaneseCorporateBondsMember 2021-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:FairValueInputsLevel2Member mfg:NonJapaneseCorporateBondsMember 2021-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:FairValueInputsLevel3Member mfg:NonJapaneseCorporateBondsMember 2021-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember mfg:NonJapaneseCorporateBondsMember 2021-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:FairValueInputsLevel3Member 2021-03-31 0001335730 us-gaap:LandMember 2021-03-31 0001335730 us-gaap:BuildingMember 2021-03-31 0001335730 us-gaap:FurnitureAndFixturesMember 2021-03-31 0001335730 us-gaap:LeaseholdImprovementsMember 2021-03-31 0001335730 us-gaap:ConstructionInProgressMember 2021-03-31 0001335730 us-gaap:SoftwareAndSoftwareDevelopmentCostsMember 2021-03-31 0001335730 us-gaap:CustomerRelationshipsMember 2021-03-31 0001335730 us-gaap:OtherIntangibleAssetsMember 2021-03-31 0001335730 mfg:BankTimeDepositsLiabilitiesMember us-gaap:GeographicDistributionDomesticMember 2021-03-31 0001335730 mfg:CertificatesOfDepositLiabilitiesMember us-gaap:GeographicDistributionDomesticMember 2021-03-31 0001335730 mfg:BankTimeDepositsLiabilitiesMember us-gaap:GeographicDistributionForeignMember 2021-03-31 0001335730 mfg:CertificatesOfDepositLiabilitiesMember us-gaap:GeographicDistributionForeignMember 2021-03-31 0001335730 mfg:MizuhoSecuritiesCompanyLimitedMember 2021-03-31 0001335730 us-gaap:FairValueInputsLevel1Member mfg:CommonStockInvestmentMember country:JP us-gaap:EquitySecuritiesMember 2021-03-31 0001335730 mfg:CommonStockInvestmentMember country:JP us-gaap:EquitySecuritiesMember 2021-03-31 0001335730 us-gaap:EquitySecuritiesMember country:JP mfg:InvestmentTrustsMember us-gaap:FairValueInputsLevel1Member 2021-03-31 0001335730 us-gaap:EquitySecuritiesMember country:JP mfg:InvestmentTrustsMember us-gaap:FairValueInputsLevel2Member 2021-03-31 0001335730 us-gaap:EquitySecuritiesMember country:JP mfg:InvestmentTrustsMember 2021-03-31 0001335730 us-gaap:DebtSecuritiesMember mfg:ForeignMember mfg:InvestmentTrustsMember us-gaap:FairValueInputsLevel2Member 2021-03-31 0001335730 us-gaap:DebtSecuritiesMember mfg:ForeignMember mfg:InvestmentTrustsMember 2021-03-31 0001335730 us-gaap:DebtSecuritiesMember mfg:ForeignMember mfg:OtherFundsMember us-gaap:FairValueInputsLevel2Member 2021-03-31 0001335730 us-gaap:DebtSecuritiesMember mfg:ForeignMember mfg:OtherFundsMember 2021-03-31 0001335730 mfg:LifeInsuranceCompaniesGeneralAccountMember mfg:AllOtherMember us-gaap:FairValueInputsLevel2Member 2021-03-31 0001335730 mfg:LifeInsuranceCompaniesGeneralAccountMember mfg:AllOtherMember 2021-03-31 0001335730 mfg:OtherInvestedAssetsMember mfg:AllOtherMember us-gaap:FairValueInputsLevel1Member 2021-03-31 0001335730 mfg:OtherInvestedAssetsMember mfg:AllOtherMember us-gaap:FairValueInputsLevel2Member 2021-03-31 0001335730 mfg:OtherInvestedAssetsMember mfg:AllOtherMember 2021-03-31 0001335730 mfg:NetAssetValueMember mfg:AllOtherMember 2021-03-31 0001335730 us-gaap:FairValueInputsLevel1Member 2021-03-31 0001335730 us-gaap:FairValueInputsLevel2Member 2021-03-31 0001335730 us-gaap:DebtSecuritiesMember country:JP mfg:GovernmentBondSecuritiesMember us-gaap:FairValueInputsLevel1Member 2021-03-31 0001335730 us-gaap:DebtSecuritiesMember country:JP mfg:GovernmentBondSecuritiesMember 2021-03-31 0001335730 us-gaap:DebtSecuritiesMember country:JP mfg:InvestmentTrustsMember us-gaap:FairValueInputsLevel2Member 2021-03-31 0001335730 us-gaap:DebtSecuritiesMember country:JP mfg:InvestmentTrustsMember 2021-03-31 0001335730 us-gaap:DebtSecuritiesMember country:JP mfg:OtherFundsMember 2021-03-31 0001335730 us-gaap:EquitySecuritiesMember mfg:ForeignMember mfg:CommonStockInvestmentMember us-gaap:FairValueInputsLevel1Member 2021-03-31 0001335730 us-gaap:EquitySecuritiesMember mfg:ForeignMember mfg:CommonStockInvestmentMember 2021-03-31 0001335730 us-gaap:EquitySecuritiesMember mfg:ForeignMember mfg:InvestmentTrustsMember us-gaap:FairValueInputsLevel2Member 2021-03-31 0001335730 us-gaap:EquitySecuritiesMember mfg:ForeignMember mfg:InvestmentTrustsMember 2021-03-31 0001335730 us-gaap:DebtSecuritiesMember mfg:ForeignMember mfg:GovernmentBondSecuritiesMember us-gaap:FairValueInputsLevel1Member 2021-03-31 0001335730 us-gaap:DebtSecuritiesMember mfg:ForeignMember mfg:GovernmentBondSecuritiesMember us-gaap:FairValueInputsLevel2Member 2021-03-31 0001335730 us-gaap:DebtSecuritiesMember mfg:ForeignMember mfg:GovernmentBondSecuritiesMember 2021-03-31 0001335730 us-gaap:DebtSecuritiesMember country:JP mfg:OtherFundsMember us-gaap:FairValueInputsLevel2Member 2021-03-31 0001335730 mfg:CommonStockInvestmentMember us-gaap:EquitySecuritiesMember 2021-03-31 0001335730 mfg:OtherCountriesMember 2021-03-31 0001335730 country:JP 2021-03-31 0001335730 country:US 2021-03-31 0001335730 country:GB 2021-03-31 0001335730 mfg:MizuhoSecuritiesCompanyLimitedMember country:JP 2021-03-31 0001335730 mfg:MizuhoFinancialGroupIncMember 2021-03-31 0001335730 mfg:SeniorBorrowingsAndDebtObligationsMember mfg:FixedRateDebtMember mfg:UnitedStatesDollarDenominatedDebtMember 2021-03-31 0001335730 mfg:SeniorBorrowingsAndDebtObligationsMember mfg:FixedRateDebtMember mfg:YenDenominatedNotesMember 2021-03-31 0001335730 mfg:SeniorBorrowingsAndDebtObligationsMember mfg:FloatingRateDebtMember mfg:OtherForeignCurrencyDenominatedDebtMember 2021-03-31 0001335730 mfg:SeniorBorrowingsAndDebtObligationsMember mfg:FloatingRateDebtMember mfg:UnitedStatesDollarDenominatedDebtMember 2021-03-31 0001335730 mfg:SeniorBorrowingsAndDebtObligationsMember mfg:FloatingRateDebtMember mfg:YenDenominatedNotesMember 2021-03-31 0001335730 mfg:SeniorBorrowingsAndDebtObligationsMember mfg:FixedRateDebtMember mfg:OtherForeignCurrencyDenominatedDebtMember 2021-03-31 0001335730 mfg:SubordinatedBorrowingsAndDebtObligationsMember 2021-03-31 0001335730 mfg:SubordinatedBorrowingsAndDebtObligationsMember mfg:FixedRateDebtMember mfg:UnitedStatesDollarDenominatedDebtMember 2021-03-31 0001335730 mfg:SubordinatedBorrowingsAndDebtObligationsMember mfg:FixedRateDebtMember mfg:YenDenominatedNotesMember 2021-03-31 0001335730 mfg:SeniorBorrowingsAndDebtObligationsMember 2021-03-31 0001335730 mfg:OthersCountriesMember 2021-03-31 0001335730 srt:EuropeMember 2021-03-31 0001335730 srt:AsiaMember 2021-03-31 0001335730 srt:ParentCompanyMember 2021-03-31 0001335730 srt:ParentCompanyMember mfg:BankingSubsidiariesMember 2021-03-31 0001335730 srt:ParentCompanyMember mfg:NonBankingSubsidiariesAndAffiliatedCompaniesMember 2021-03-31 0001335730 us-gaap:EquityMethodInvesteeMember 2021-03-31 0001335730 mfg:DomesticDebtSecuritiesMember 2021-03-31 0001335730 us-gaap:AccruedIncomeReceivableMember 2021-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:HousingLoanMember us-gaap:SpecialMentionMember 2021-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionForeignMember mfg:CorporateRatingMember mfg:NonAccrualLoansMember 2021-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionForeignMember mfg:CorporateRatingMember us-gaap:SpecialMentionMember 2021-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionForeignMember mfg:CorporateRatingMember us-gaap:PassMember 2021-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionDomesticMember 2021-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionDomesticMember mfg:BanksAndFinancialInstitutionsMember mfg:NonAccrualLoansMember 2021-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionDomesticMember mfg:BanksAndFinancialInstitutionsMember us-gaap:SpecialMentionMember 2021-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionDomesticMember mfg:BanksAndFinancialInstitutionsMember us-gaap:PassMember 2021-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionDomesticMember mfg:SoverignMember mfg:NonAccrualLoansMember 2021-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionDomesticMember mfg:SoverignMember us-gaap:SpecialMentionMember 2021-03-31 0001335730 us-gaap:PassMember mfg:SoverignMember us-gaap:GeographicDistributionDomesticMember mfg:FinancingReceivablesNotImpairedMember 2021-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionForeignMember mfg:RetailRatingMember us-gaap:PassMember 2021-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionForeignMember mfg:RetailRatingMember us-gaap:SpecialMentionMember 2021-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionForeignMember mfg:RetailRatingMember mfg:NonAccrualLoansMember 2021-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionForeignMember mfg:SoverignMember us-gaap:PassMember 2021-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionForeignMember mfg:SoverignMember us-gaap:SpecialMentionMember 2021-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionForeignMember mfg:SoverignMember mfg:NonAccrualLoansMember 2021-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionForeignMember mfg:BanksAndFinancialInstitutionsMember us-gaap:PassMember 2021-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionForeignMember mfg:BanksAndFinancialInstitutionsMember us-gaap:SpecialMentionMember 2021-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionForeignMember mfg:BanksAndFinancialInstitutionsMember mfg:NonAccrualLoansMember 2021-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionForeignMember 2021-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember 2021-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:SmallAndMediumSizedCompaniesMember us-gaap:SpecialMentionMember 2021-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:OtherMember us-gaap:PassMember 2021-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:HousingLoanMember mfg:NonAccrualLoansMember 2021-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:OtherMember mfg:NonAccrualLoansMember 2021-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:OtherMember us-gaap:SpecialMentionMember 2021-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:SmallAndMediumSizedCompaniesMember us-gaap:PassMember 2021-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember mfg:NonAccrualLoansMember us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:LargeCompaniesMember 2021-03-31 0001335730 us-gaap:PassMember us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:FinancingReceivablesNotImpairedMember mfg:LargeCompaniesMember 2021-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:SpecialMentionMember us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:LargeCompaniesMember 2021-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:SmallAndMediumSizedCompaniesMember mfg:NonAccrualLoansMember 2021-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:HousingLoanMember us-gaap:PassMember 2021-03-31 0001335730 mfg:SubjectToEnforceableMasterNettingArragementMember 2021-03-31 0001335730 mfg:GovernmentBondsMember 2021-03-31 0001335730 mfg:NetOfAllowanceForCreditLossMember 2021-03-31 0001335730 us-gaap:AccruedIncomeReceivableMember mfg:AvailableForSaleAndHeldToMaturitySecuritiesMember 2021-03-31 0001335730 mfg:FinancingReceivablesImpairedMember 2021-03-31 0001335730 mfg:OtherMember us-gaap:GeographicDistributionDomesticMember mfg:CurrentMember mfg:RetailRatingMember 2021-03-31 0001335730 mfg:SoverignMember us-gaap:FinancingReceivables30To59DaysPastDueMember us-gaap:GeographicDistributionDomesticMember 2021-03-31 0001335730 mfg:SoverignMember us-gaap:FinancingReceivables60To89DaysPastDueMember us-gaap:GeographicDistributionDomesticMember 2021-03-31 0001335730 mfg:SoverignMember us-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember us-gaap:GeographicDistributionDomesticMember 2021-03-31 0001335730 mfg:SoverignMember mfg:TotalPastDueMember us-gaap:GeographicDistributionDomesticMember 2021-03-31 0001335730 mfg:BanksAndFinancialInstitutionsMember us-gaap:FinancingReceivables30To59DaysPastDueMember us-gaap:GeographicDistributionDomesticMember 2021-03-31 0001335730 mfg:BanksAndFinancialInstitutionsMember us-gaap:FinancingReceivables60To89DaysPastDueMember us-gaap:GeographicDistributionDomesticMember 2021-03-31 0001335730 mfg:BanksAndFinancialInstitutionsMember us-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember us-gaap:GeographicDistributionDomesticMember 2021-03-31 0001335730 mfg:BanksAndFinancialInstitutionsMember mfg:TotalPastDueMember us-gaap:GeographicDistributionDomesticMember 2021-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember us-gaap:FinancingReceivables30To59DaysPastDueMember mfg:LargeCompaniesMember 2021-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember us-gaap:FinancingReceivables60To89DaysPastDueMember mfg:LargeCompaniesMember 2021-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember us-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember mfg:LargeCompaniesMember 2021-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:TotalPastDueMember mfg:LargeCompaniesMember 2021-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:CurrentMember mfg:LargeCompaniesMember 2021-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:TotalMember mfg:LargeCompaniesMember 2021-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember us-gaap:FinancingReceivables30To59DaysPastDueMember mfg:SmallAndMediumSizedCompaniesMember 2021-03-31 0001335730 mfg:SoverignMember mfg:TotalMember us-gaap:GeographicDistributionDomesticMember 2021-03-31 0001335730 mfg:SoverignMember mfg:CurrentMember us-gaap:GeographicDistributionDomesticMember 2021-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:TotalMember mfg:OtherMember 2021-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:TotalPastDueMember mfg:OtherMember 2021-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember us-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember mfg:OtherMember 2021-03-31 0001335730 us-gaap:FinancingReceivables60To89DaysPastDueMember mfg:OtherMember mfg:RetailRatingMember us-gaap:GeographicDistributionDomesticMember 2021-03-31 0001335730 us-gaap:FinancingReceivables30To59DaysPastDueMember mfg:OtherMember mfg:RetailRatingMember us-gaap:GeographicDistributionDomesticMember 2021-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:TotalMember mfg:HousingLoanMember 2021-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:CurrentMember mfg:HousingLoanMember 2021-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:TotalPastDueMember mfg:HousingLoanMember 2021-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember us-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember mfg:HousingLoanMember 2021-03-31 0001335730 mfg:HousingLoanMember mfg:RetailRatingMember us-gaap:GeographicDistributionDomesticMember us-gaap:FinancingReceivables60To89DaysPastDueMember 2021-03-31 0001335730 mfg:HousingLoanMember mfg:RetailRatingMember us-gaap:GeographicDistributionDomesticMember us-gaap:FinancingReceivables30To59DaysPastDueMember 2021-03-31 0001335730 mfg:CorporateRatingMember us-gaap:GeographicDistributionDomesticMember mfg:TotalMember mfg:SmallAndMediumSizedCompaniesMember 2021-03-31 0001335730 mfg:CorporateRatingMember us-gaap:GeographicDistributionDomesticMember mfg:CurrentMember mfg:SmallAndMediumSizedCompaniesMember 2021-03-31 0001335730 mfg:CorporateRatingMember us-gaap:GeographicDistributionDomesticMember mfg:TotalPastDueMember mfg:SmallAndMediumSizedCompaniesMember 2021-03-31 0001335730 us-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:SmallAndMediumSizedCompaniesMember 2021-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember us-gaap:FinancingReceivables60To89DaysPastDueMember mfg:SmallAndMediumSizedCompaniesMember 2021-03-31 0001335730 mfg:TotalMember 2021-03-31 0001335730 mfg:CurrentMember 2021-03-31 0001335730 mfg:TotalPastDueMember 2021-03-31 0001335730 us-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember 2021-03-31 0001335730 us-gaap:FinancingReceivables60To89DaysPastDueMember 2021-03-31 0001335730 us-gaap:FinancingReceivables30To59DaysPastDueMember 2021-03-31 0001335730 us-gaap:GeographicDistributionForeignMember mfg:TotalMember 2021-03-31 0001335730 us-gaap:GeographicDistributionForeignMember mfg:CurrentMember 2021-03-31 0001335730 us-gaap:GeographicDistributionForeignMember mfg:TotalPastDueMember 2021-03-31 0001335730 us-gaap:GeographicDistributionForeignMember us-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember 2021-03-31 0001335730 us-gaap:GeographicDistributionForeignMember us-gaap:FinancingReceivables60To89DaysPastDueMember 2021-03-31 0001335730 us-gaap:GeographicDistributionForeignMember us-gaap:FinancingReceivables30To59DaysPastDueMember 2021-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:TotalMember 2021-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CurrentMember 2021-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:TotalPastDueMember 2021-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember us-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember 2021-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember us-gaap:FinancingReceivables60To89DaysPastDueMember 2021-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember us-gaap:FinancingReceivables30To59DaysPastDueMember 2021-03-31 0001335730 mfg:BanksAndFinancialInstitutionsMember mfg:TotalMember us-gaap:GeographicDistributionDomesticMember 2021-03-31 0001335730 mfg:BanksAndFinancialInstitutionsMember mfg:CurrentMember us-gaap:GeographicDistributionDomesticMember 2021-03-31 0001335730 mfg:SecuritiesRelatedBusinessMember 2020-04-01 2021-03-31 0001335730 us-gaap:CorrespondentClearingMember 2020-04-01 2021-03-31 0001335730 us-gaap:InvestmentAdvisoryManagementAndAdministrativeServiceMember 2020-04-01 2021-03-31 0001335730 us-gaap:FiduciaryAndTrustMember 2020-04-01 2021-03-31 0001335730 mfg:AgencyBusinessMember 2020-04-01 2021-03-31 0001335730 mfg:GuaranteeRelatedBusinessMember 2020-04-01 2021-03-31 0001335730 us-gaap:FinancialServiceOtherMember 2020-04-01 2021-03-31 0001335730 us-gaap:FinancialServiceMember 2020-04-01 2021-03-31 0001335730 mfg:DepositsRelatedBusinessMember 2020-04-01 2021-03-31 0001335730 mfg:LendingRelatedBusinessMember 2020-04-01 2021-03-31 0001335730 us-gaap:AvailableforsaleSecuritiesMember 2020-04-01 2021-03-31 0001335730 us-gaap:ForeignExchangeMember 2020-04-01 2021-03-31 0001335730 us-gaap:LoansMember us-gaap:CreditRiskContractMember 2020-04-01 2021-03-31 0001335730 mfg:PeriodFiveMember 2020-04-01 2021-03-31 0001335730 mfg:FinancialInstrumentsHedgingForeignExchangeRiskMember 2020-04-01 2021-03-31 0001335730 mfg:LargeCompaniesMember mfg:CorporateRatingMember us-gaap:GeographicDistributionDomesticMember 2020-04-01 2021-03-31 0001335730 mfg:SmallAndMediumSizedCompaniesMember mfg:CorporateRatingMember us-gaap:GeographicDistributionDomesticMember 2020-04-01 2021-03-31 0001335730 mfg:HousingLoanMember mfg:RetailRatingMember us-gaap:GeographicDistributionDomesticMember 2020-04-01 2021-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:OtherMember 2020-04-01 2021-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember 2020-04-01 2021-03-31 0001335730 us-gaap:GeographicDistributionForeignMember 2020-04-01 2021-03-31 0001335730 mfg:BanksAndFinancialInstitutionsMember us-gaap:GeographicDistributionDomesticMember 2020-04-01 2021-03-31 0001335730 mfg:PeriodFourMember 2020-04-01 2021-03-31 0001335730 mfg:TradingAccountGainsMember 2020-04-01 2021-03-31 0001335730 us-gaap:LongTermDebtMember 2020-04-01 2021-03-31 0001335730 mfg:GlobalMarketsCompanyMember us-gaap:ExchangeTradedFundsMember 2020-04-01 2021-03-31 0001335730 us-gaap:ExchangeTradedFundsMember 2020-04-01 2021-03-31 0001335730 mfg:TradingSecuritiesMember 2020-04-01 2021-03-31 0001335730 us-gaap:ResidentialPortfolioSegmentMember 2020-04-01 2021-03-31 0001335730 us-gaap:CommercialPortfolioSegmentMember 2020-04-01 2021-03-31 0001335730 us-gaap:DebtSecuritiesMember 2020-04-01 2021-03-31 0001335730 mfg:DerivedMember 2020-04-01 2021-03-31 0001335730 us-gaap:EquitySecuritiesMember 2020-04-01 2021-03-31 0001335730 us-gaap:InterestRateContractMember 2020-04-01 2021-03-31 0001335730 us-gaap:ForeignExchangeContractMember 2020-04-01 2021-03-31 0001335730 us-gaap:EquityContractMember 2020-04-01 2021-03-31 0001335730 us-gaap:CreditRiskContractMember 2020-04-01 2021-03-31 0001335730 us-gaap:OtherContractMember 2020-04-01 2021-03-31 0001335730 us-gaap:SeniorDebtObligationsMember 2020-04-01 2021-03-31 0001335730 us-gaap:AccumulatedForeignCurrencyAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember 2020-04-01 2021-03-31 0001335730 us-gaap:TreasuryStockMember 2020-04-01 2021-03-31 0001335730 us-gaap:PropertyPlantAndEquipmentMember 2020-04-01 2021-03-31 0001335730 mfg:RetailAndBusinessBankingCompanyMember us-gaap:OperatingSegmentsMember 2020-04-01 2021-03-31 0001335730 mfg:CorporateAndInstitutionalCompanyMember us-gaap:OperatingSegmentsMember 2020-04-01 2021-03-31 0001335730 mfg:GlobalCorporateCompanyMember us-gaap:OperatingSegmentsMember 2020-04-01 2021-03-31 0001335730 mfg:GlobalMarketsCompanyMember us-gaap:OperatingSegmentsMember 2020-04-01 2021-03-31 0001335730 mfg:AssetManagementCompanyMember us-gaap:OperatingSegmentsMember 2020-04-01 2021-03-31 0001335730 us-gaap:IntersegmentEliminationMember 2020-04-01 2021-03-31 0001335730 mfg:AccumulatedOwnCreditRiskAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember 2020-04-01 2021-03-31 0001335730 us-gaap:AccumulatedDefinedBenefitPlansAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember 2020-04-01 2021-03-31 0001335730 us-gaap:AccumulatedNetInvestmentGainLossIncludingPortionAttributableToNoncontrollingInterestMember 2020-04-01 2021-03-31 0001335730 us-gaap:CommonStockMember 2020-04-01 2021-03-31 0001335730 us-gaap:AccumulatedOtherComprehensiveIncomeMember 2020-04-01 2021-03-31 0001335730 us-gaap:RetainedEarningsMember 2020-04-01 2021-03-31 0001335730 mfg:TradingSecuritiesMember us-gaap:AllOtherCorporateBondsMember 2020-04-01 2021-03-31 0001335730 mfg:TradingSecuritiesMember us-gaap:EquitySecuritiesMember 2020-04-01 2021-03-31 0001335730 us-gaap:DerivativeFinancialInstrumentsAssetsMember us-gaap:InterestRateContractMember 2020-04-01 2021-03-31 0001335730 us-gaap:DerivativeFinancialInstrumentsAssetsMember us-gaap:ForeignExchangeContractMember 2020-04-01 2021-03-31 0001335730 us-gaap:DerivativeFinancialInstrumentsAssetsMember us-gaap:EquityContractMember 2020-04-01 2021-03-31 0001335730 us-gaap:DerivativeFinancialInstrumentsAssetsMember mfg:CreditRelatedContractsMember 2020-04-01 2021-03-31 0001335730 us-gaap:AvailableforsaleSecuritiesMember mfg:JapaneseCorporateBondsMember 2020-04-01 2021-03-31 0001335730 us-gaap:AvailableforsaleSecuritiesMember us-gaap:OtherThanSecuritiesInvestmentMember 2020-04-01 2021-03-31 0001335730 us-gaap:AvailableforsaleSecuritiesMember mfg:NonJapaneseCorporateBondsMember 2020-04-01 2021-03-31 0001335730 us-gaap:NoncontrollingInterestMember 2020-04-01 2021-03-31 0001335730 us-gaap:AvailableforsaleSecuritiesMember us-gaap:CommercialMortgageBackedSecuritiesMember 2020-04-01 2021-03-31 0001335730 mfg:TradingSecuritiesMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2020-04-01 2021-03-31 0001335730 us-gaap:DerivativeFinancialInstrumentsAssetsMember us-gaap:OtherContractMember 2020-04-01 2021-03-31 0001335730 us-gaap:AvailableforsaleSecuritiesMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2020-04-01 2021-03-31 0001335730 us-gaap:SecuritiesSoldNotYetPurchasedMember 2020-04-01 2021-03-31 0001335730 us-gaap:AccountingStandardsUpdate201409Member 2020-04-01 2021-03-31 0001335730 srt:MaximumMember 2020-04-01 2021-03-31 0001335730 srt:MinimumMember 2020-04-01 2021-03-31 0001335730 mfg:TradingSecuritiesMember 2020-04-01 2021-03-31 0001335730 us-gaap:GeneralAndAdministrativeExpenseMember 2020-04-01 2021-03-31 0001335730 us-gaap:OccupancyMember 2020-04-01 2021-03-31 0001335730 mfg:EntityWideSoftwareMember 2020-04-01 2021-03-31 0001335730 mfg:MizuhoSecuritiesCompanyLimitedMember country:JP 2020-04-01 2021-03-31 0001335730 mfg:StockCompensationPlan1Member 2020-04-01 2021-03-31 0001335730 mfg:StockCompensationPlan2Member 2020-04-01 2021-03-31 0001335730 mfg:StockCompensationPlan1Member us-gaap:PerformanceSharesMember 2020-04-01 2021-03-31 0001335730 mfg:StockCompensationPlan2Member us-gaap:PerformanceSharesMember 2020-04-01 2021-03-31 0001335730 srt:AsiaMember 2020-04-01 2021-03-31 0001335730 srt:EuropeMember 2020-04-01 2021-03-31 0001335730 mfg:OthersCountriesMember 2020-04-01 2021-03-31 0001335730 country:US 2020-04-01 2021-03-31 0001335730 country:JP 2020-04-01 2021-03-31 0001335730 mfg:NonBankingSubsidiariesAndAffiliatedCompaniesMember srt:ParentCompanyMember 2020-04-01 2021-03-31 0001335730 mfg:BankingSubsidiaryMember srt:ParentCompanyMember 2020-04-01 2021-03-31 0001335730 srt:ParentCompanyMember 2020-04-01 2021-03-31 0001335730 us-gaap:EquityMethodInvesteeMember 2020-04-01 2021-03-31 0001335730 mfg:GlobalCorporateCompanyOrRetailAndBusinessBankingCompanyMember 2020-04-01 2021-03-31 0001335730 us-gaap:OtherLiabilitiesMember 2020-04-01 2021-03-31 0001335730 us-gaap:NetInvestmentHedgingMember 2020-04-01 2021-03-31 0001335730 mfg:ClassSixteenPreferredStockMember 2022-03-31 0001335730 mfg:ClassFifteenPreferredStockMember 2022-03-31 0001335730 mfg:ClassFourteenPreferredStockMember 2022-03-31 0001335730 us-gaap:MortgageBackedSecuritiesOtherMember mfg:DomesticGovernmentSponsoredEnterprisesDebtSecuritiesMember us-gaap:DebtSecuritiesMember 2022-03-31 0001335730 us-gaap:ForeignCorporateDebtSecuritiesMember us-gaap:DebtSecuritiesMember 2022-03-31 0001335730 us-gaap:DebtSecuritiesMember mfg:DomesticDebtSecuritiesMember 2022-03-31 0001335730 us-gaap:CommercialMortgageBackedSecuritiesMember us-gaap:DebtSecuritiesMember 2022-03-31 0001335730 us-gaap:ResidentialMortgageBackedSecuritiesMember us-gaap:DebtSecuritiesMember 2022-03-31 0001335730 us-gaap:MortgageBackedSecuritiesOtherMember us-gaap:DebtSecuritiesMember 2022-03-31 0001335730 mfg:ForeignGovernmentBondsMember us-gaap:DebtSecuritiesMember 2022-03-31 0001335730 us-gaap:USTreasuryAndGovernmentShorttermDebtSecuritiesMember us-gaap:DebtSecuritiesMember 2022-03-31 0001335730 us-gaap:MunicipalBondsMember us-gaap:DebtSecuritiesMember 2022-03-31 0001335730 mfg:GovernmentBondsMember us-gaap:DebtSecuritiesMember 2022-03-31 0001335730 mfg:GovernmentBondsMember us-gaap:DebtSecuritiesMember us-gaap:AvailableforsaleSecuritiesMember 2022-03-31 0001335730 us-gaap:MunicipalBondsMember us-gaap:DebtSecuritiesMember us-gaap:AvailableforsaleSecuritiesMember 2022-03-31 0001335730 us-gaap:USTreasuryAndGovernmentShorttermDebtSecuritiesMember us-gaap:DebtSecuritiesMember us-gaap:AvailableforsaleSecuritiesMember 2022-03-31 0001335730 mfg:ForeignGovernmentBondsMember us-gaap:DebtSecuritiesMember us-gaap:AvailableforsaleSecuritiesMember 2022-03-31 0001335730 us-gaap:MortgageBackedSecuritiesOtherMember us-gaap:DebtSecuritiesMember us-gaap:AvailableforsaleSecuritiesMember 2022-03-31 0001335730 us-gaap:ResidentialMortgageBackedSecuritiesMember us-gaap:DebtSecuritiesMember us-gaap:AvailableforsaleSecuritiesMember 2022-03-31 0001335730 us-gaap:CommercialMortgageBackedSecuritiesMember us-gaap:DebtSecuritiesMember us-gaap:AvailableforsaleSecuritiesMember 2022-03-31 0001335730 mfg:DomesticDebtSecuritiesMember us-gaap:DebtSecuritiesMember us-gaap:AvailableforsaleSecuritiesMember 2022-03-31 0001335730 us-gaap:DebtSecuritiesMember us-gaap:ForeignCorporateDebtSecuritiesMember us-gaap:AvailableforsaleSecuritiesMember 2022-03-31 0001335730 us-gaap:DebtSecuritiesMember us-gaap:AvailableforsaleSecuritiesMember 2022-03-31 0001335730 us-gaap:DebtSecuritiesMember mfg:ForeignAgencyMortgageBackedSecuritiesMember us-gaap:MortgageBackedSecuritiesOtherMember 2022-03-31 0001335730 us-gaap:DebtSecuritiesMember mfg:NegotiableCertificatesOfDepositsAssetBackedSecuritiesAndCollateralLoanObligationsMember 2022-03-31 0001335730 mfg:MizuhoFinancialGroupInc.Member 2022-03-31 0001335730 us-gaap:PerformanceGuaranteeMember 2022-03-31 0001335730 us-gaap:PerformanceGuaranteeMember mfg:ExpirationPeriodOneYearOrLessMember 2022-03-31 0001335730 us-gaap:PerformanceGuaranteeMember mfg:ExpirationPeriodAfterOneYearThroughFiveYearsMember 2022-03-31 0001335730 us-gaap:PerformanceGuaranteeMember mfg:ExpirationPeriodAfterFiveYearsMember 2022-03-31 0001335730 us-gaap:FinancialGuaranteeMember 2022-03-31 0001335730 us-gaap:FinancialGuaranteeMember mfg:ExpirationPeriodOneYearOrLessMember 2022-03-31 0001335730 us-gaap:FinancialGuaranteeMember mfg:ExpirationPeriodAfterOneYearThroughFiveYearsMember 2022-03-31 0001335730 us-gaap:FinancialGuaranteeMember mfg:ExpirationPeriodAfterFiveYearsMember 2022-03-31 0001335730 us-gaap:MarketValueGuaranteeMember 2022-03-31 0001335730 us-gaap:MarketValueGuaranteeMember mfg:ExpirationPeriodOneYearOrLessMember 2022-03-31 0001335730 us-gaap:MarketValueGuaranteeMember mfg:ExpirationPeriodAfterOneYearThroughFiveYearsMember 2022-03-31 0001335730 us-gaap:GuaranteeTypeOtherMember 2022-03-31 0001335730 us-gaap:GuaranteeTypeOtherMember mfg:ExpirationPeriodOneYearOrLessMember 2022-03-31 0001335730 us-gaap:GuaranteeTypeOtherMember mfg:ExpirationPeriodAfterOneYearThroughFiveYearsMember 2022-03-31 0001335730 us-gaap:GuaranteeTypeOtherMember mfg:ExpirationPeriodAfterFiveYearsMember 2022-03-31 0001335730 mfg:GuaranteesForRepaymentOfTrustPrincipalMember 2022-03-31 0001335730 mfg:ExpirationPeriodOneYearOrLessMember mfg:GuaranteesForRepaymentOfTrustPrincipalMember 2022-03-31 0001335730 mfg:GuaranteesForRepaymentOfTrustPrincipalMember mfg:ExpirationPeriodAfterOneYearThroughFiveYearsMember 2022-03-31 0001335730 mfg:GuaranteesForRepaymentOfTrustPrincipalMember mfg:ExpirationPeriodAfterFiveYearsMember 2022-03-31 0001335730 mfg:GuaranteesOnTrustAccountsMember 2022-03-31 0001335730 mfg:GuaranteesOnTrustAccountsMember mfg:ExpirationPeriodOneYearOrLessMember 2022-03-31 0001335730 mfg:GuaranteesOnTrustAccountsMember mfg:ExpirationPeriodAfterOneYearThroughFiveYearsMember 2022-03-31 0001335730 mfg:GuaranteesOnTrustAccountsMember mfg:ExpirationPeriodAfterFiveYearsMember 2022-03-31 0001335730 us-gaap:PaymentGuaranteeMember 2022-03-31 0001335730 us-gaap:PaymentGuaranteeMember mfg:ExpirationPeriodOneYearOrLessMember 2022-03-31 0001335730 us-gaap:PaymentGuaranteeMember mfg:ExpirationPeriodAfterOneYearThroughFiveYearsMember 2022-03-31 0001335730 us-gaap:PaymentGuaranteeMember mfg:ExpirationPeriodAfterFiveYearsMember 2022-03-31 0001335730 mfg:ExpirationPeriodAfterFiveYearsMember us-gaap:MarketValueGuaranteeMember 2022-03-31 0001335730 mfg:ExpirationPeriodOneYearOrLessMember 2022-03-31 0001335730 mfg:ExpirationPeriodAfterOneYearThroughFiveYearsMember 2022-03-31 0001335730 mfg:ExpirationPeriodAfterFiveYearsMember 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember 2022-03-31 0001335730 us-gaap:ResidentialMortgageBackedSecuritiesMember mfg:AvailableForSaleAndTradingSecuritiesMember 2022-03-31 0001335730 us-gaap:AllOtherCorporateBondsMember mfg:AvailableForSaleAndTradingSecuritiesMember 2022-03-31 0001335730 mfg:DebtInstrumentMember 2022-03-31 0001335730 us-gaap:MaturityUpTo30DaysMember 2022-03-31 0001335730 mfg:Maturity31To90DaysMember 2022-03-31 0001335730 us-gaap:MaturityOver90DaysMember 2022-03-31 0001335730 mfg:MaturityOvernightAndOpenMember 2022-03-31 0001335730 mfg:ImpairedFinancingReceivablesWithNoRelatedAllowanceMember 2022-03-31 0001335730 mfg:MarketableEquitySecuritiesMember 2022-03-31 0001335730 mfg:SecuritizationsMember 2022-03-31 0001335730 mfg:LoanParticipationsMember 2022-03-31 0001335730 us-gaap:DerivativeMember us-gaap:InterestRateContractMember 2022-03-31 0001335730 us-gaap:ForeignExchangeContractMember us-gaap:DerivativeMember 2022-03-31 0001335730 us-gaap:EquityContractMember us-gaap:DerivativeMember 2022-03-31 0001335730 us-gaap:CreditRiskContractMember us-gaap:DerivativeMember 2022-03-31 0001335730 mfg:OtherContractsMember us-gaap:DerivativeMember 2022-03-31 0001335730 mfg:MizuhoFinancialGroupIncMember mfg:JapanGaapConsolidatedMember 2022-03-31 0001335730 mfg:MizuhoBankLimitedMember mfg:JapanGaapConsolidatedMember 2022-03-31 0001335730 mfg:JapanGaapConsolidatedMember mfg:MizuhoTrustBankingCompanyLimitedMember 2022-03-31 0001335730 mfg:JapanGaapUnconsolidatedAffiliatesMember mfg:MizuhoBankLimitedMember 2022-03-31 0001335730 mfg:MizuhoTrustBankingCompanyLimitedMember mfg:JapanGaapUnconsolidatedAffiliatesMember 2022-03-31 0001335730 mfg:CreditRiskContractPurchasedMember 2022-03-31 0001335730 mfg:CreditRiskContractWrittenMember us-gaap:ExternalCreditRatingInvestmentGradeMember 2022-03-31 0001335730 mfg:CreditRiskContractWrittenMember us-gaap:ExternalCreditRatingNonInvestmentGradeMember 2022-03-31 0001335730 mfg:CreditRiskContractWrittenMember 2022-03-31 0001335730 us-gaap:RiskLevelLowMember mfg:PerformanceFinancialMarketValueAndOtherTypeGuaranteeMember 2022-03-31 0001335730 us-gaap:RiskLevelHighMember mfg:PerformanceFinancialMarketValueAndOtherTypeGuaranteeMember 2022-03-31 0001335730 mfg:PerformanceFinancialMarketValueAndOtherTypeGuaranteeMember 2022-03-31 0001335730 us-gaap:CommitmentsToExtendCreditMember 2022-03-31 0001335730 us-gaap:UnusedLinesOfCreditMember 2022-03-31 0001335730 us-gaap:LongTermDebtMember 2022-03-31 0001335730 us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMember mfg:MizuhoFinancialGroupIncMember 2022-03-31 0001335730 us-gaap:FairValueMeasurementsNonrecurringMember 2022-03-31 0001335730 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsNonrecurringMember 2022-03-31 0001335730 us-gaap:PortionAtOtherThanFairValueFairValueDisclosureMember us-gaap:FairValueMeasurementsNonrecurringMember 2022-03-31 0001335730 country:JP mfg:MizuhoSecuritiesCompanyLimitedMember 2022-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember 2022-03-31 0001335730 us-gaap:GeographicDistributionForeignMember 2022-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:LargeCompaniesMember 2022-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:SmallAndMediumSizedCompaniesMember 2022-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:HousingLoanMember 2022-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:OtherMember 2022-03-31 0001335730 mfg:OricoMember 2022-03-31 0001335730 mfg:ChibaKogyaBankLtdMember 2022-03-31 0001335730 mfg:JointStockCommercialBankForeignTradeOfVietnamMember 2022-03-31 0001335730 mfg:MizuhoLeasingCompanyLtdMember 2022-03-31 0001335730 mfg:MatthewInternationalCapitalManagementLlcMember 2022-03-31 0001335730 mfg:CustodyBankOfJapanLtdMember 2022-03-31 0001335730 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsNonrecurringMember 2022-03-31 0001335730 srt:MinimumMember us-gaap:MeasurementInputPrepaymentRateMember mfg:AvailableForSaleAndTradingSecuritiesMember mfg:DiscountedCashFlowsValuationTechniqueMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2022-03-31 0001335730 srt:MaximumMember us-gaap:MeasurementInputPrepaymentRateMember mfg:AvailableForSaleAndTradingSecuritiesMember mfg:DiscountedCashFlowsValuationTechniqueMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2022-03-31 0001335730 srt:MinimumMember us-gaap:MeasurementInputDefaultRateMember mfg:AvailableForSaleAndTradingSecuritiesMember mfg:DiscountedCashFlowsValuationTechniqueMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2022-03-31 0001335730 srt:MaximumMember us-gaap:MeasurementInputDefaultRateMember mfg:AvailableForSaleAndTradingSecuritiesMember mfg:DiscountedCashFlowsValuationTechniqueMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2022-03-31 0001335730 srt:MinimumMember mfg:MeasurementInputRecoveryRateMember mfg:AvailableForSaleAndTradingSecuritiesMember mfg:DiscountedCashFlowsValuationTechniqueMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2022-03-31 0001335730 srt:MaximumMember mfg:MeasurementInputRecoveryRateMember mfg:AvailableForSaleAndTradingSecuritiesMember mfg:DiscountedCashFlowsValuationTechniqueMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2022-03-31 0001335730 srt:MinimumMember us-gaap:MeasurementInputDiscountRateMember mfg:AvailableForSaleAndTradingSecuritiesMember mfg:DiscountedCashFlowsValuationTechniqueMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2022-03-31 0001335730 srt:MaximumMember us-gaap:MeasurementInputDiscountRateMember mfg:AvailableForSaleAndTradingSecuritiesMember mfg:DiscountedCashFlowsValuationTechniqueMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2022-03-31 0001335730 mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:ResidentialMortgageBackedSecuritiesMember srt:WeightedAverageMember us-gaap:MeasurementInputPrepaymentRateMember mfg:DiscountedCashFlowsValuationTechniqueMember 2022-03-31 0001335730 mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:ResidentialMortgageBackedSecuritiesMember srt:WeightedAverageMember us-gaap:MeasurementInputDefaultRateMember mfg:DiscountedCashFlowsValuationTechniqueMember 2022-03-31 0001335730 mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:ResidentialMortgageBackedSecuritiesMember srt:WeightedAverageMember mfg:MeasurementInputRecoveryRateMember mfg:DiscountedCashFlowsValuationTechniqueMember 2022-03-31 0001335730 mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:ResidentialMortgageBackedSecuritiesMember srt:WeightedAverageMember us-gaap:MeasurementInputDiscountRateMember mfg:DiscountedCashFlowsValuationTechniqueMember 2022-03-31 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember us-gaap:AllOtherCorporateBondsMember srt:MinimumMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:MeasurementInputPrepaymentRateMember 2022-03-31 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember us-gaap:AllOtherCorporateBondsMember srt:MaximumMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:MeasurementInputPrepaymentRateMember 2022-03-31 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember us-gaap:AllOtherCorporateBondsMember srt:MinimumMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:MeasurementInputDefaultRateMember 2022-03-31 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember us-gaap:AllOtherCorporateBondsMember srt:MaximumMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:MeasurementInputDefaultRateMember 2022-03-31 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember us-gaap:AllOtherCorporateBondsMember srt:MinimumMember mfg:AvailableForSaleAndTradingSecuritiesMember mfg:MeasurementInputRecoveryRateMember 2022-03-31 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember us-gaap:AllOtherCorporateBondsMember srt:MaximumMember mfg:AvailableForSaleAndTradingSecuritiesMember mfg:MeasurementInputRecoveryRateMember 2022-03-31 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember us-gaap:AllOtherCorporateBondsMember srt:MinimumMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:MeasurementInputDiscountRateMember 2022-03-31 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember us-gaap:AllOtherCorporateBondsMember srt:MaximumMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:MeasurementInputDiscountRateMember 2022-03-31 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember us-gaap:AllOtherCorporateBondsMember srt:MinimumMember mfg:AvailableForSaleAndTradingSecuritiesMember mfg:MeasurementInputDiscountRate1Member 2022-03-31 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember us-gaap:AllOtherCorporateBondsMember srt:MaximumMember mfg:AvailableForSaleAndTradingSecuritiesMember mfg:MeasurementInputDiscountRate1Member 2022-03-31 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember us-gaap:AllOtherCorporateBondsMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:MeasurementInputPrepaymentRateMember srt:WeightedAverageMember 2022-03-31 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember us-gaap:AllOtherCorporateBondsMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:MeasurementInputDefaultRateMember srt:WeightedAverageMember 2022-03-31 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember us-gaap:AllOtherCorporateBondsMember mfg:AvailableForSaleAndTradingSecuritiesMember mfg:MeasurementInputRecoveryRateMember srt:WeightedAverageMember 2022-03-31 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember us-gaap:AllOtherCorporateBondsMember mfg:AvailableForSaleAndTradingSecuritiesMember us-gaap:MeasurementInputDiscountRateMember srt:WeightedAverageMember 2022-03-31 0001335730 mfg:DiscountedCashFlowsValuationTechniqueMember us-gaap:AllOtherCorporateBondsMember mfg:AvailableForSaleAndTradingSecuritiesMember mfg:MeasurementInputDiscountRate1Member srt:WeightedAverageMember 2022-03-31 0001335730 us-gaap:HeldtomaturitySecuritiesMember us-gaap:DebtSecuritiesMember 2022-03-31 0001335730 us-gaap:MortgageBackedSecuritiesOtherMember us-gaap:DebtSecuritiesMember us-gaap:HeldtomaturitySecuritiesMember 2022-03-31 0001335730 mfg:GovernmentBondsMember us-gaap:DebtSecuritiesMember us-gaap:HeldtomaturitySecuritiesMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:InterestRateContractMember us-gaap:DerivativeMember mfg:MeasurementInputIRIRCorrelationMember srt:MinimumMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:InterestRateContractMember us-gaap:DerivativeMember mfg:MeasurementInputIRIRCorrelationMember srt:MaximumMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:InterestRateContractMember us-gaap:DerivativeMember mfg:MeasurementInputIRIRCorrelationMember srt:WeightedAverageMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:ForeignExchangeContractMember srt:MinimumMember mfg:MeasurementInputFXIRCorrelationMember us-gaap:DerivativeMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:ForeignExchangeContractMember srt:MaximumMember mfg:MeasurementInputFXIRCorrelationMember us-gaap:DerivativeMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:ForeignExchangeContractMember srt:WeightedAverageMember mfg:MeasurementInputFXIRCorrelationMember us-gaap:DerivativeMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:ForeignExchangeContractMember srt:MinimumMember mfg:MeasurementInputFXFXCorrelationMember us-gaap:DerivativeMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:ForeignExchangeContractMember srt:MaximumMember mfg:MeasurementInputFXFXCorrelationMember us-gaap:DerivativeMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:ForeignExchangeContractMember srt:WeightedAverageMember mfg:MeasurementInputFXFXCorrelationMember us-gaap:DerivativeMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:EquityContractMember srt:MinimumMember mfg:MeasurementInputEquityIRCorrelationMember us-gaap:DerivativeMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:EquityContractMember srt:MaximumMember mfg:MeasurementInputEquityIRCorrelationMember us-gaap:DerivativeMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:EquityContractMember srt:MinimumMember mfg:MeasurementInputEquityCorrelationMember us-gaap:DerivativeMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:EquityContractMember srt:MaximumMember mfg:MeasurementInputEquityCorrelationMember us-gaap:DerivativeMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:EquityContractMember srt:MinimumMember mfg:MeasurementInputEquityVolatilityMember us-gaap:DerivativeMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:EquityContractMember srt:MaximumMember mfg:MeasurementInputEquityVolatilityMember us-gaap:DerivativeMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:EquityContractMember srt:WeightedAverageMember mfg:MeasurementInputEquityIRCorrelationMember us-gaap:DerivativeMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:EquityContractMember srt:WeightedAverageMember mfg:MeasurementInputEquityCorrelationMember us-gaap:DerivativeMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:EquityContractMember srt:WeightedAverageMember mfg:MeasurementInputEquityVolatilityMember us-gaap:DerivativeMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:CreditRiskContractMember us-gaap:MeasurementInputDefaultRateMember srt:MinimumMember us-gaap:DerivativeMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:CreditRiskContractMember us-gaap:MeasurementInputDefaultRateMember srt:MaximumMember us-gaap:DerivativeMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:CreditRiskContractMember mfg:MeasurementInputCreditCorrelationMember srt:MinimumMember us-gaap:DerivativeMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:CreditRiskContractMember mfg:MeasurementInputCreditCorrelationMember srt:MaximumMember us-gaap:DerivativeMember 2022-03-31 0001335730 us-gaap:CreditRiskContractMember mfg:InternalValuationModelMember us-gaap:DerivativeMember us-gaap:MeasurementInputDefaultRateMember srt:WeightedAverageMember 2022-03-31 0001335730 us-gaap:CreditRiskContractMember mfg:InternalValuationModelMember us-gaap:DerivativeMember mfg:MeasurementInputCreditCorrelationMember srt:WeightedAverageMember 2022-03-31 0001335730 mfg:InternalValuationModelMember mfg:OtherContractsMember us-gaap:DerivativeMember mfg:MeasurementInputCommodityVolatilityMember srt:MinimumMember 2022-03-31 0001335730 mfg:InternalValuationModelMember mfg:OtherContractsMember us-gaap:DerivativeMember mfg:MeasurementInputCommodityVolatilityMember srt:WeightedAverageMember 2022-03-31 0001335730 mfg:OtherContractsMember mfg:InternalValuationModelMember us-gaap:DerivativeMember mfg:MeasurementInputCommodityVolatilityMember srt:MaximumMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputIRIRCorrelationMember srt:MinimumMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputIRIRCorrelationMember srt:MaximumMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputFXIRCorrelationMember srt:MinimumMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputFXIRCorrelationMember srt:MaximumMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputFXFXCorrelationMember srt:MinimumMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputFXFXCorrelationMember srt:MaximumMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputEquityIRCorrelationMember srt:MinimumMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputEquityIRCorrelationMember srt:MaximumMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputEquityFXCorrelationMember srt:MinimumMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputEquityFXCorrelationMember srt:MaximumMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputEquityCorrelationMember srt:MinimumMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputEquityCorrelationMember srt:MaximumMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputEquityVolatilityMember srt:MinimumMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputEquityVolatilityMember srt:MaximumMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember us-gaap:MeasurementInputDefaultRateMember srt:MinimumMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember us-gaap:MeasurementInputDefaultRateMember srt:MaximumMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputCreditCorrelationMember srt:MinimumMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputCreditCorrelationMember srt:MaximumMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputIRIRCorrelationMember srt:WeightedAverageMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputFXIRCorrelationMember srt:WeightedAverageMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputFXFXCorrelationMember srt:WeightedAverageMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputEquityIRCorrelationMember srt:WeightedAverageMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputEquityFXCorrelationMember srt:WeightedAverageMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputEquityCorrelationMember srt:WeightedAverageMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputEquityVolatilityMember srt:WeightedAverageMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember us-gaap:MeasurementInputDefaultRateMember srt:WeightedAverageMember 2022-03-31 0001335730 mfg:InternalValuationModelMember us-gaap:LongTermDebtMember mfg:MeasurementInputCreditCorrelationMember srt:WeightedAverageMember 2022-03-31 0001335730 mfg:OtherSecuritiesMember 2022-03-31 0001335730 mfg:JapaneseGovernmentBondsLocalGovernmentBondsMember 2022-03-31 0001335730 mfg:ForeignGovernmentBondsAndForeignAgencyMortgageBackedSecuritiesMember 2022-03-31 0001335730 mfg:CommercialPaperAndCorporateBondsMember 2022-03-31 0001335730 mfg:EquitySecuritiesInSecuredBorrowingsMember 2022-03-31 0001335730 us-gaap:CarryingReportedAmountFairValueDisclosureMember 2022-03-31 0001335730 us-gaap:EstimateOfFairValueFairValueDisclosureMember 2022-03-31 0001335730 us-gaap:EstimateOfFairValueFairValueDisclosureMember us-gaap:FairValueInputsLevel1Member 2022-03-31 0001335730 us-gaap:EstimateOfFairValueFairValueDisclosureMember us-gaap:FairValueInputsLevel2Member 2022-03-31 0001335730 us-gaap:AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember us-gaap:VariableInterestEntityPrimaryBeneficiaryMember 2022-03-31 0001335730 mfg:AssetBackedSecuritizationsMember us-gaap:VariableInterestEntityPrimaryBeneficiaryMember 2022-03-31 0001335730 mfg:AssetBackedSecuritizationsMember us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMember 2022-03-31 0001335730 mfg:InvestmentsInSecuritizationProductsMember us-gaap:VariableInterestEntityPrimaryBeneficiaryMember 2022-03-31 0001335730 us-gaap:SecuritiesInvestmentMember us-gaap:VariableInterestEntityPrimaryBeneficiaryMember 2022-03-31 0001335730 us-gaap:SecuritiesInvestmentMember us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMember 2022-03-31 0001335730 mfg:TrustAccountsMember us-gaap:VariableInterestEntityPrimaryBeneficiaryMember 2022-03-31 0001335730 us-gaap:VariableInterestEntityPrimaryBeneficiaryMember 2022-03-31 0001335730 us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMember 2022-03-31 0001335730 us-gaap:SeniorDebtObligationsMember 2022-03-31 0001335730 us-gaap:EstimateOfFairValueFairValueDisclosureMember us-gaap:FairValueInputsLevel3Member 2022-03-31 0001335730 us-gaap:InterestRateContractMember 2022-03-31 0001335730 us-gaap:ForeignExchangeContractMember 2022-03-31 0001335730 us-gaap:EquityContractMember 2022-03-31 0001335730 us-gaap:CreditRiskContractMember 2022-03-31 0001335730 us-gaap:OtherContractMember 2022-03-31 0001335730 mfg:AssetBackedSecuritizationsMember 2022-03-31 0001335730 us-gaap:SecuritiesInvestmentMember 2022-03-31 0001335730 us-gaap:NondesignatedMember 2022-03-31 0001335730 us-gaap:NondesignatedMember us-gaap:InterestRateContractMember 2022-03-31 0001335730 us-gaap:ForeignExchangeContractMember us-gaap:NondesignatedMember 2022-03-31 0001335730 us-gaap:EquityContractMember us-gaap:NondesignatedMember 2022-03-31 0001335730 us-gaap:CreditRiskContractMember us-gaap:NondesignatedMember 2022-03-31 0001335730 us-gaap:OtherContractMember us-gaap:NondesignatedMember 2022-03-31 0001335730 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:FairValueInputsLevel2Member 2022-03-31 0001335730 us-gaap:EquitySecuritiesMember us-gaap:FairValueMeasurementsRecurringMember 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember mfg:GovernmentBondsMember us-gaap:FairValueInputsLevel1Member 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember mfg:GovernmentBondsMember us-gaap:FairValueInputsLevel2Member 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember mfg:GovernmentBondsMember 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:MunicipalBondsMember us-gaap:FairValueInputsLevel2Member 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:MunicipalBondsMember 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:USTreasuryAndGovernmentShorttermDebtSecuritiesMember us-gaap:FairValueInputsLevel1Member 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:USTreasuryAndGovernmentShorttermDebtSecuritiesMember us-gaap:FairValueInputsLevel2Member 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:USTreasuryAndGovernmentShorttermDebtSecuritiesMember 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember mfg:ForeignGovernmentBondsMember us-gaap:FairValueInputsLevel1Member 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember mfg:ForeignGovernmentBondsMember us-gaap:FairValueInputsLevel2Member 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember mfg:ForeignGovernmentBondsMember 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:MortgageBackedSecuritiesOtherMember us-gaap:FairValueInputsLevel2Member 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:MortgageBackedSecuritiesOtherMember 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:ResidentialMortgageBackedSecuritiesMember us-gaap:FairValueInputsLevel3Member 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember mfg:CertificatesOfDepositAndCommercialPaperMember us-gaap:FairValueInputsLevel2Member 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember mfg:CertificatesOfDepositAndCommercialPaperMember 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:AllOtherCorporateBondsMember us-gaap:FairValueInputsLevel1Member 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:AllOtherCorporateBondsMember us-gaap:FairValueInputsLevel2Member 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:AllOtherCorporateBondsMember us-gaap:FairValueInputsLevel3Member 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:AllOtherCorporateBondsMember 2022-03-31 0001335730 us-gaap:FairValueInputsLevel1Member us-gaap:EquitySecuritiesMember us-gaap:FairValueMeasurementsRecurringMember 2022-03-31 0001335730 us-gaap:FairValueInputsLevel2Member us-gaap:EquitySecuritiesMember us-gaap:FairValueMeasurementsRecurringMember 2022-03-31 0001335730 us-gaap:FairValueInputsLevel3Member us-gaap:EquitySecuritiesMember us-gaap:FairValueMeasurementsRecurringMember 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:InterestRateContractMember us-gaap:FairValueInputsLevel1Member 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:FairValueInputsLevel2Member us-gaap:InterestRateContractMember 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:InterestRateContractMember us-gaap:FairValueInputsLevel3Member 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:InterestRateContractMember 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:ForeignExchangeContractMember us-gaap:FairValueInputsLevel2Member 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:ForeignExchangeContractMember us-gaap:FairValueInputsLevel3Member 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:ForeignExchangeContractMember 2022-03-31 0001335730 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:EquityContractMember 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:FairValueInputsLevel2Member us-gaap:EquityContractMember 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:FairValueInputsLevel3Member us-gaap:EquityContractMember 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:EquityContractMember 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:FairValueInputsLevel2Member us-gaap:CreditRiskContractMember 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:FairValueInputsLevel3Member us-gaap:CreditRiskContractMember 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:CreditRiskContractMember 2022-03-31 0001335730 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:OtherContractMember 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:FairValueInputsLevel2Member us-gaap:OtherContractMember 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:FairValueInputsLevel3Member us-gaap:OtherContractMember 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:OtherContractMember 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:FairValueInputsLevel2Member us-gaap:ResidentialMortgageBackedSecuritiesMember 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:CommercialMortgageBackedSecuritiesMember 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:FairValueInputsLevel2Member mfg:JapaneseCorporateBondsMember 2022-03-31 0001335730 mfg:JapaneseCorporateBondsMember us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember mfg:JapaneseCorporateBondsMember 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:FairValueInputsLevel2Member mfg:NonJapaneseCorporateBondsMember 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:FairValueInputsLevel3Member mfg:NonJapaneseCorporateBondsMember 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember mfg:NonJapaneseCorporateBondsMember 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:FairValueInputsLevel2Member us-gaap:CommercialMortgageBackedSecuritiesMember 2022-03-31 0001335730 us-gaap:FairValueMeasurementsRecurringMember us-gaap:FairValueInputsLevel3Member 2022-03-31 0001335730 us-gaap:LandMember 2022-03-31 0001335730 us-gaap:BuildingMember 2022-03-31 0001335730 us-gaap:FurnitureAndFixturesMember 2022-03-31 0001335730 us-gaap:LeaseholdImprovementsMember 2022-03-31 0001335730 us-gaap:ConstructionInProgressMember 2022-03-31 0001335730 us-gaap:SoftwareAndSoftwareDevelopmentCostsMember 2022-03-31 0001335730 us-gaap:CustomerRelationshipsMember 2022-03-31 0001335730 us-gaap:OtherIntangibleAssetsMember 2022-03-31 0001335730 mfg:JapanGaapRetainedEarningsMember 2022-03-31 0001335730 mfg:JapanGaapAdditionalPaidinCapitalMember 2022-03-31 0001335730 mfg:BankTimeDepositsLiabilitiesMember us-gaap:GeographicDistributionDomesticMember 2022-03-31 0001335730 mfg:CertificatesOfDepositLiabilitiesMember us-gaap:GeographicDistributionDomesticMember 2022-03-31 0001335730 mfg:BankTimeDepositsLiabilitiesMember us-gaap:GeographicDistributionForeignMember 2022-03-31 0001335730 us-gaap:GeographicDistributionForeignMember mfg:CertificatesOfDepositLiabilitiesMember 2022-03-31 0001335730 mfg:BanktimeDepositsLiabilitiesDomesticMember 2022-03-31 0001335730 mfg:CertificatesOfDepositLiabilitiesDomesticMember 2022-03-31 0001335730 mfg:CertificatesOfDepositLiabilitiesForeignMember 2022-03-31 0001335730 mfg:BanktimeDepositsLiabilitiesForeignMember 2022-03-31 0001335730 mfg:CertificatesOfDepositLiabilitiesMember 2022-03-31 0001335730 mfg:BankTimeDepositsLiabilitiesMember 2022-03-31 0001335730 mfg:PeriodEightMember 2022-03-31 0001335730 mfg:PeriodSevenMember 2022-03-31 0001335730 mfg:PeriodSixMember 2022-03-31 0001335730 mfg:PeriodFiveMember 2022-03-31 0001335730 mfg:PeriodEightMember mfg:TierIMember 2022-03-31 0001335730 mfg:PeriodSevenMember mfg:TierIMember 2022-03-31 0001335730 mfg:PeriodSixMember mfg:TierIMember 2022-03-31 0001335730 mfg:PeriodFiveMember mfg:TierIMember 2022-03-31 0001335730 mfg:PeriodEightMember mfg:CommonEquityTierOneCapitalMember 2022-03-31 0001335730 mfg:PeriodSevenMember mfg:CommonEquityTierOneCapitalMember 2022-03-31 0001335730 mfg:PeriodSixMember mfg:CommonEquityTierOneCapitalMember 2022-03-31 0001335730 mfg:PeriodFiveMember mfg:CommonEquityTierOneCapitalMember 2022-03-31 0001335730 mfg:BaselIiiMember srt:MinimumMember 2022-03-31 0001335730 srt:MinimumMember mfg:RegulatoryReportingMember 2022-03-31 0001335730 srt:MinimumMember mfg:TemporarySuspensionMember 2022-03-31 0001335730 mfg:BaselIiiMember 2022-03-31 0001335730 mfg:MizuhoSecuritiesCompanyLimitedMember 2022-03-31 0001335730 us-gaap:EquitySecuritiesMember country:JP 2022-03-31 0001335730 us-gaap:DebtSecuritiesMember country:JP 2022-03-31 0001335730 us-gaap:EquitySecuritiesMember mfg:ForeignMember 2022-03-31 0001335730 us-gaap:DebtSecuritiesMember mfg:ForeignMember 2022-03-31 0001335730 mfg:GeneralAccountAssetsMember 2022-03-31 0001335730 mfg:DefinedBenefitPlanOtherAssetMember 2022-03-31 0001335730 country:JP us-gaap:EquitySecuritiesMember mfg:CommonStockInvestmentMember us-gaap:FairValueInputsLevel1Member 2022-03-31 0001335730 country:JP mfg:CommonStockInvestmentMember us-gaap:EquitySecuritiesMember 2022-03-31 0001335730 us-gaap:DebtSecuritiesMember mfg:ForeignMember mfg:GovernmentBondSecuritiesMember us-gaap:FairValueInputsLevel2Member 2022-03-31 0001335730 us-gaap:DebtSecuritiesMember mfg:ForeignMember mfg:GovernmentBondSecuritiesMember 2022-03-31 0001335730 us-gaap:DebtSecuritiesMember mfg:ForeignMember mfg:InvestmentTrustsMember us-gaap:FairValueInputsLevel2Member 2022-03-31 0001335730 us-gaap:DebtSecuritiesMember mfg:ForeignMember mfg:InvestmentTrustsMember 2022-03-31 0001335730 us-gaap:DebtSecuritiesMember mfg:ForeignMember mfg:OtherFundsMember us-gaap:FairValueInputsLevel2Member 2022-03-31 0001335730 us-gaap:DebtSecuritiesMember mfg:ForeignMember mfg:OtherFundsMember 2022-03-31 0001335730 mfg:LifeInsuranceCompaniesGeneralAccountMember mfg:AllOtherMember us-gaap:FairValueInputsLevel2Member 2022-03-31 0001335730 mfg:LifeInsuranceCompaniesGeneralAccountMember mfg:AllOtherMember 2022-03-31 0001335730 mfg:OtherInvestedAssetsMember mfg:AllOtherMember us-gaap:FairValueInputsLevel1Member 2022-03-31 0001335730 mfg:OtherInvestedAssetsMember mfg:AllOtherMember us-gaap:FairValueInputsLevel2Member 2022-03-31 0001335730 mfg:OtherInvestedAssetsMember mfg:AllOtherMember 2022-03-31 0001335730 mfg:NetAssetValueMember mfg:AllOtherMember 2022-03-31 0001335730 us-gaap:FairValueInputsLevel1Member 2022-03-31 0001335730 us-gaap:FairValueInputsLevel2Member 2022-03-31 0001335730 us-gaap:EquitySecuritiesMember country:JP mfg:InvestmentTrustsMember us-gaap:FairValueInputsLevel1Member 2022-03-31 0001335730 us-gaap:EquitySecuritiesMember country:JP mfg:InvestmentTrustsMember us-gaap:FairValueInputsLevel2Member 2022-03-31 0001335730 us-gaap:EquitySecuritiesMember country:JP mfg:InvestmentTrustsMember 2022-03-31 0001335730 us-gaap:DebtSecuritiesMember country:JP mfg:GovernmentBondSecuritiesMember us-gaap:FairValueInputsLevel1Member 2022-03-31 0001335730 us-gaap:DebtSecuritiesMember country:JP mfg:GovernmentBondSecuritiesMember 2022-03-31 0001335730 us-gaap:DebtSecuritiesMember country:JP mfg:InvestmentTrustsMember us-gaap:FairValueInputsLevel2Member 2022-03-31 0001335730 us-gaap:DebtSecuritiesMember country:JP mfg:InvestmentTrustsMember 2022-03-31 0001335730 us-gaap:DebtSecuritiesMember country:JP mfg:OtherFundsMember us-gaap:FairValueInputsLevel2Member 2022-03-31 0001335730 us-gaap:DebtSecuritiesMember country:JP mfg:OtherFundsMember 2022-03-31 0001335730 us-gaap:EquitySecuritiesMember mfg:ForeignMember mfg:CommonStockInvestmentMember us-gaap:FairValueInputsLevel1Member 2022-03-31 0001335730 us-gaap:EquitySecuritiesMember mfg:ForeignMember mfg:CommonStockInvestmentMember 2022-03-31 0001335730 us-gaap:EquitySecuritiesMember mfg:ForeignMember mfg:InvestmentTrustsMember us-gaap:FairValueInputsLevel2Member 2022-03-31 0001335730 us-gaap:EquitySecuritiesMember mfg:ForeignMember mfg:InvestmentTrustsMember 2022-03-31 0001335730 us-gaap:DebtSecuritiesMember mfg:ForeignMember mfg:GovernmentBondSecuritiesMember us-gaap:FairValueInputsLevel1Member 2022-03-31 0001335730 mfg:CommonStockInvestmentMember us-gaap:EquitySecuritiesMember 2022-03-31 0001335730 country:JP 2022-03-31 0001335730 country:US 2022-03-31 0001335730 mfg:OtherCountriesMember 2022-03-31 0001335730 country:GB 2022-03-31 0001335730 mfg:MizuhoFinancialGroupInc.Member country:JP 2022-03-31 0001335730 mfg:MhfgStockPlanMember 2022-03-31 0001335730 mfg:MizuhoFinancialGroupIncMember 2022-03-31 0001335730 mfg:ExpireInTwentyTwentyThreeMember 2022-03-31 0001335730 mfg:ExpireInTwentyTwentyFourMember 2022-03-31 0001335730 mfg:ExpireInTwentyTwentyFiveMember 2022-03-31 0001335730 mfg:ExpireInTwentyTwentySixMember 2022-03-31 0001335730 mfg:YearOfExpiryTwoThousandAndTwentySevenMember 2022-03-31 0001335730 mfg:YearOfExpiryTwoThousandAndTwentyEightAndThereafterMember 2022-03-31 0001335730 mfg:FixedRateDebtMember mfg:YenDenominatedNotesMember mfg:SeniorBorrowingsAndDebtObligationsMember srt:MinimumMember 2022-03-31 0001335730 mfg:FixedRateDebtMember mfg:YenDenominatedNotesMember mfg:SeniorBorrowingsAndDebtObligationsMember srt:MaximumMember 2022-03-31 0001335730 mfg:FixedRateDebtMember mfg:UnitedStatesDollarDenominatedDebtMember mfg:SeniorBorrowingsAndDebtObligationsMember srt:MinimumMember 2022-03-31 0001335730 mfg:FixedRateDebtMember mfg:UnitedStatesDollarDenominatedDebtMember mfg:SeniorBorrowingsAndDebtObligationsMember srt:MaximumMember 2022-03-31 0001335730 mfg:OtherForeignCurrencyDenominatedDebtMember mfg:FixedRateDebtMember mfg:SeniorBorrowingsAndDebtObligationsMember srt:MinimumMember 2022-03-31 0001335730 mfg:OtherForeignCurrencyDenominatedDebtMember mfg:FixedRateDebtMember mfg:SeniorBorrowingsAndDebtObligationsMember srt:MaximumMember 2022-03-31 0001335730 mfg:FloatingRateDebtMember mfg:SeniorBorrowingsAndDebtObligationsMember mfg:YenDenominatedNotesMember srt:MinimumMember 2022-03-31 0001335730 mfg:FloatingRateDebtMember mfg:SeniorBorrowingsAndDebtObligationsMember mfg:YenDenominatedNotesMember srt:MaximumMember 2022-03-31 0001335730 mfg:FloatingRateDebtMember mfg:SeniorBorrowingsAndDebtObligationsMember mfg:UnitedStatesDollarDenominatedDebtMember srt:MinimumMember 2022-03-31 0001335730 mfg:FloatingRateDebtMember mfg:SeniorBorrowingsAndDebtObligationsMember mfg:UnitedStatesDollarDenominatedDebtMember srt:MaximumMember 2022-03-31 0001335730 mfg:FloatingRateDebtMember mfg:OtherForeignCurrencyDenominatedDebtMember mfg:SeniorBorrowingsAndDebtObligationsMember srt:MinimumMember 2022-03-31 0001335730 mfg:FloatingRateDebtMember mfg:OtherForeignCurrencyDenominatedDebtMember mfg:SeniorBorrowingsAndDebtObligationsMember srt:MaximumMember 2022-03-31 0001335730 mfg:FixedRateDebtMember mfg:YenDenominatedNotesMember mfg:SubordinatedBorrowingsAndDebtObligationsMember srt:MinimumMember 2022-03-31 0001335730 mfg:FixedRateDebtMember mfg:YenDenominatedNotesMember mfg:SubordinatedBorrowingsAndDebtObligationsMember srt:MaximumMember 2022-03-31 0001335730 mfg:FixedRateDebtMember mfg:SubordinatedBorrowingsAndDebtObligationsMember mfg:UnitedStatesDollarDenominatedDebtMember srt:MinimumMember 2022-03-31 0001335730 mfg:FixedRateDebtMember mfg:SubordinatedBorrowingsAndDebtObligationsMember mfg:UnitedStatesDollarDenominatedDebtMember srt:MaximumMember 2022-03-31 0001335730 mfg:SeniorBorrowingsAndDebtObligationsMember mfg:FixedRateDebtMember mfg:UnitedStatesDollarDenominatedDebtMember 2022-03-31 0001335730 mfg:SeniorBorrowingsAndDebtObligationsMember mfg:FixedRateDebtMember mfg:YenDenominatedNotesMember 2022-03-31 0001335730 mfg:SeniorBorrowingsAndDebtObligationsMember mfg:FloatingRateDebtMember mfg:OtherForeignCurrencyDenominatedDebtMember 2022-03-31 0001335730 mfg:SeniorBorrowingsAndDebtObligationsMember mfg:FloatingRateDebtMember mfg:UnitedStatesDollarDenominatedDebtMember 2022-03-31 0001335730 mfg:SeniorBorrowingsAndDebtObligationsMember mfg:FloatingRateDebtMember mfg:YenDenominatedNotesMember 2022-03-31 0001335730 mfg:SeniorBorrowingsAndDebtObligationsMember mfg:FixedRateDebtMember mfg:OtherForeignCurrencyDenominatedDebtMember 2022-03-31 0001335730 mfg:SubordinatedBorrowingsAndDebtObligationsMember 2022-03-31 0001335730 mfg:SubordinatedBorrowingsAndDebtObligationsMember mfg:FixedRateDebtMember mfg:UnitedStatesDollarDenominatedDebtMember 2022-03-31 0001335730 mfg:SubordinatedBorrowingsAndDebtObligationsMember mfg:FixedRateDebtMember mfg:YenDenominatedNotesMember 2022-03-31 0001335730 mfg:SeniorBorrowingsAndDebtObligationsMember 2022-03-31 0001335730 srt:AsiaMember 2022-03-31 0001335730 mfg:OthersCountriesMember 2022-03-31 0001335730 srt:EuropeMember 2022-03-31 0001335730 srt:ParentCompanyMember 2022-03-31 0001335730 srt:ParentCompanyMember mfg:BankingSubsidiariesMember 2022-03-31 0001335730 srt:ParentCompanyMember mfg:NonBankingSubsidiariesAndAffiliatedCompaniesMember 2022-03-31 0001335730 us-gaap:EquityMethodInvesteeMember 2022-03-31 0001335730 mfg:DomesticDebtSecuritiesMember 2022-03-31 0001335730 us-gaap:AccruedIncomeReceivableMember 2022-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionForeignMember mfg:BanksAndFinancialInstitutionsMember us-gaap:SpecialMentionMember 2022-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionForeignMember mfg:SoverignMember mfg:NonAccrualLoansMember 2022-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember 2022-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionForeignMember mfg:BanksAndFinancialInstitutionsMember mfg:NonAccrualLoansMember 2022-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionForeignMember 2022-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionForeignMember mfg:BanksAndFinancialInstitutionsMember us-gaap:PassMember 2022-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionDomesticMember mfg:SoverignMember mfg:NonAccrualLoansMember 2022-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionDomesticMember mfg:SoverignMember us-gaap:SpecialMentionMember 2022-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:OtherMember us-gaap:PassMember 2022-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionDomesticMember mfg:SoverignMember us-gaap:PassMember 2022-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:HousingLoanMember mfg:NonAccrualLoansMember 2022-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:OtherMember mfg:NonAccrualLoansMember 2022-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:OtherMember us-gaap:SpecialMentionMember 2022-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:SpecialMentionMember us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:LargeCompaniesMember 2022-03-31 0001335730 mfg:LargeCompaniesMember mfg:FinancingReceivablesNotImpairedMember mfg:CorporateRatingMember us-gaap:GeographicDistributionDomesticMember us-gaap:PassMember 2022-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:HousingLoanMember us-gaap:PassMember 2022-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionDomesticMember mfg:BanksAndFinancialInstitutionsMember us-gaap:SpecialMentionMember 2022-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionForeignMember mfg:SoverignMember us-gaap:SpecialMentionMember 2022-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionDomesticMember mfg:BanksAndFinancialInstitutionsMember mfg:NonAccrualLoansMember 2022-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:SmallAndMediumSizedCompaniesMember us-gaap:SpecialMentionMember 2022-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:SmallAndMediumSizedCompaniesMember us-gaap:PassMember 2022-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember mfg:NonAccrualLoansMember us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:LargeCompaniesMember 2022-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:SmallAndMediumSizedCompaniesMember mfg:NonAccrualLoansMember 2022-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionForeignMember mfg:RetailRatingMember mfg:NonAccrualLoansMember 2022-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionForeignMember mfg:SoverignMember us-gaap:PassMember 2022-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionForeignMember mfg:RetailRatingMember us-gaap:SpecialMentionMember 2022-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionForeignMember mfg:RetailRatingMember us-gaap:PassMember 2022-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionForeignMember mfg:CorporateRatingMember mfg:NonAccrualLoansMember 2022-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionForeignMember mfg:CorporateRatingMember us-gaap:SpecialMentionMember 2022-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionForeignMember mfg:CorporateRatingMember us-gaap:PassMember 2022-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionDomesticMember 2022-03-31 0001335730 mfg:FinancingReceivablesNotImpairedMember us-gaap:GeographicDistributionDomesticMember mfg:BanksAndFinancialInstitutionsMember us-gaap:PassMember 2022-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:HousingLoanMember us-gaap:SpecialMentionMember 2022-03-31 0001335730 mfg:SubjectToEnforceableMasterNettingArragementMember 2022-03-31 0001335730 mfg:GovernmentBondsMember 2022-03-31 0001335730 mfg:NetOfAllowanceForCreditLossMember 2022-03-31 0001335730 mfg:AvailableForSaleAndHeldToMaturitySecuritiesMember us-gaap:AccruedIncomeReceivableMember 2022-03-31 0001335730 mfg:FinancingReceivablesImpairedMember 2022-03-31 0001335730 us-gaap:NationalTaxAgencyJapanMember mfg:MizuhoFinancialGroupInc.Member 2022-03-31 0001335730 us-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember mfg:BanksAndFinancialInstitutionsMember us-gaap:GeographicDistributionDomesticMember 2022-03-31 0001335730 mfg:BanksAndFinancialInstitutionsMember us-gaap:FinancingReceivables60To89DaysPastDueMember us-gaap:GeographicDistributionDomesticMember 2022-03-31 0001335730 mfg:BanksAndFinancialInstitutionsMember us-gaap:FinancingReceivables30To59DaysPastDueMember us-gaap:GeographicDistributionDomesticMember 2022-03-31 0001335730 mfg:SoverignMember mfg:TotalMember us-gaap:GeographicDistributionDomesticMember 2022-03-31 0001335730 mfg:SoverignMember mfg:CurrentMember us-gaap:GeographicDistributionDomesticMember 2022-03-31 0001335730 mfg:SoverignMember mfg:TotalPastDueMember us-gaap:GeographicDistributionDomesticMember 2022-03-31 0001335730 us-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember mfg:SoverignMember us-gaap:GeographicDistributionDomesticMember 2022-03-31 0001335730 mfg:SoverignMember us-gaap:FinancingReceivables60To89DaysPastDueMember us-gaap:GeographicDistributionDomesticMember 2022-03-31 0001335730 mfg:SoverignMember us-gaap:FinancingReceivables30To59DaysPastDueMember us-gaap:GeographicDistributionDomesticMember 2022-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:OtherMember mfg:TotalMember 2022-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:OtherMember mfg:CurrentMember 2022-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:OtherMember mfg:TotalPastDueMember 2022-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember us-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember mfg:RetailRatingMember mfg:OtherMember 2022-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:OtherMember us-gaap:FinancingReceivables60To89DaysPastDueMember 2022-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:OtherMember us-gaap:FinancingReceivables30To59DaysPastDueMember 2022-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:HousingLoanMember mfg:TotalMember 2022-03-31 0001335730 us-gaap:FinancingReceivables60To89DaysPastDueMember 2022-03-31 0001335730 us-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember 2022-03-31 0001335730 mfg:TotalPastDueMember 2022-03-31 0001335730 mfg:CurrentMember 2022-03-31 0001335730 mfg:TotalMember 2022-03-31 0001335730 us-gaap:FinancingReceivables30To59DaysPastDueMember 2022-03-31 0001335730 us-gaap:GeographicDistributionForeignMember mfg:TotalMember 2022-03-31 0001335730 us-gaap:GeographicDistributionForeignMember mfg:CurrentMember 2022-03-31 0001335730 us-gaap:GeographicDistributionForeignMember mfg:TotalPastDueMember 2022-03-31 0001335730 us-gaap:GeographicDistributionForeignMember us-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember 2022-03-31 0001335730 us-gaap:GeographicDistributionForeignMember us-gaap:FinancingReceivables60To89DaysPastDueMember 2022-03-31 0001335730 us-gaap:GeographicDistributionForeignMember us-gaap:FinancingReceivables30To59DaysPastDueMember 2022-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:TotalMember 2022-03-31 0001335730 mfg:CurrentMember us-gaap:GeographicDistributionDomesticMember 2022-03-31 0001335730 mfg:TotalPastDueMember us-gaap:GeographicDistributionDomesticMember 2022-03-31 0001335730 us-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember us-gaap:GeographicDistributionDomesticMember 2022-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember us-gaap:FinancingReceivables60To89DaysPastDueMember 2022-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember us-gaap:FinancingReceivables30To59DaysPastDueMember 2022-03-31 0001335730 mfg:BanksAndFinancialInstitutionsMember mfg:TotalMember us-gaap:GeographicDistributionDomesticMember 2022-03-31 0001335730 mfg:BanksAndFinancialInstitutionsMember mfg:CurrentMember us-gaap:GeographicDistributionDomesticMember 2022-03-31 0001335730 mfg:TotalPastDueMember mfg:BanksAndFinancialInstitutionsMember us-gaap:GeographicDistributionDomesticMember 2022-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:LargeCompaniesMember us-gaap:FinancingReceivables30To59DaysPastDueMember 2022-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:HousingLoanMember mfg:CurrentMember 2022-03-31 0001335730 mfg:HousingLoanMember mfg:RetailRatingMember us-gaap:GeographicDistributionDomesticMember mfg:TotalPastDueMember 2022-03-31 0001335730 mfg:HousingLoanMember mfg:RetailRatingMember us-gaap:GeographicDistributionDomesticMember us-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember 2022-03-31 0001335730 mfg:RetailRatingMember us-gaap:GeographicDistributionDomesticMember mfg:HousingLoanMember us-gaap:FinancingReceivables60To89DaysPastDueMember 2022-03-31 0001335730 mfg:RetailRatingMember us-gaap:GeographicDistributionDomesticMember mfg:HousingLoanMember us-gaap:FinancingReceivables30To59DaysPastDueMember 2022-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:SmallAndMediumSizedCompaniesMember mfg:TotalMember 2022-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:SmallAndMediumSizedCompaniesMember mfg:CurrentMember 2022-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:SmallAndMediumSizedCompaniesMember mfg:TotalPastDueMember 2022-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:SmallAndMediumSizedCompaniesMember us-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember 2022-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:SmallAndMediumSizedCompaniesMember us-gaap:FinancingReceivables60To89DaysPastDueMember 2022-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:SmallAndMediumSizedCompaniesMember us-gaap:FinancingReceivables30To59DaysPastDueMember 2022-03-31 0001335730 mfg:LargeCompaniesMember mfg:CorporateRatingMember us-gaap:GeographicDistributionDomesticMember mfg:TotalMember 2022-03-31 0001335730 mfg:LargeCompaniesMember mfg:CorporateRatingMember us-gaap:GeographicDistributionDomesticMember mfg:CurrentMember 2022-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:LargeCompaniesMember mfg:TotalPastDueMember 2022-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:LargeCompaniesMember us-gaap:FinancingReceivablesEqualToGreaterThan90DaysPastDueMember 2022-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:LargeCompaniesMember us-gaap:FinancingReceivables60To89DaysPastDueMember 2022-03-31 0001335730 mfg:SecuritiesRelatedBusinessMember 2019-04-01 2020-03-31 0001335730 us-gaap:CorrespondentClearingMember 2019-04-01 2020-03-31 0001335730 us-gaap:InvestmentAdvisoryManagementAndAdministrativeServiceMember 2019-04-01 2020-03-31 0001335730 us-gaap:FiduciaryAndTrustMember 2019-04-01 2020-03-31 0001335730 mfg:AgencyBusinessMember 2019-04-01 2020-03-31 0001335730 mfg:GuaranteeRelatedBusinessMember 2019-04-01 2020-03-31 0001335730 us-gaap:FinancialServiceOtherMember 2019-04-01 2020-03-31 0001335730 us-gaap:FinancialServiceMember 2019-04-01 2020-03-31 0001335730 mfg:DepositsRelatedBusinessMember 2019-04-01 2020-03-31 0001335730 mfg:LendingRelatedBusinessMember 2019-04-01 2020-03-31 0001335730 us-gaap:ForeignExchangeMember 2019-04-01 2020-03-31 0001335730 us-gaap:LoansMember us-gaap:CreditRiskContractMember 2019-04-01 2020-03-31 0001335730 mfg:FinancialInstrumentsHedgingForeignExchangeRiskMember 2019-04-01 2020-03-31 0001335730 mfg:TradingAccountGainsMember 2019-04-01 2020-03-31 0001335730 mfg:GlobalMarketsCompanyMember us-gaap:ExchangeTradedFundsMember 2019-04-01 2020-03-31 0001335730 us-gaap:ExchangeTradedFundsMember 2019-04-01 2020-03-31 0001335730 us-gaap:ResidentialPortfolioSegmentMember 2019-04-01 2020-03-31 0001335730 us-gaap:CommercialPortfolioSegmentMember 2019-04-01 2020-03-31 0001335730 us-gaap:DebtSecuritiesMember 2019-04-01 2020-03-31 0001335730 us-gaap:EquitySecuritiesMember 2019-04-01 2020-03-31 0001335730 us-gaap:InterestRateContractMember 2019-04-01 2020-03-31 0001335730 us-gaap:ForeignExchangeContractMember 2019-04-01 2020-03-31 0001335730 us-gaap:EquityContractMember 2019-04-01 2020-03-31 0001335730 us-gaap:CreditRiskContractMember 2019-04-01 2020-03-31 0001335730 us-gaap:OtherContractMember 2019-04-01 2020-03-31 0001335730 us-gaap:AccumulatedForeignCurrencyAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember 2019-04-01 2020-03-31 0001335730 us-gaap:TreasuryStockMember 2019-04-01 2020-03-31 0001335730 us-gaap:PropertyPlantAndEquipmentMember 2019-04-01 2020-03-31 0001335730 mfg:RetailAndBusinessBankingCompanyMember us-gaap:OperatingSegmentsMember 2019-04-01 2020-03-31 0001335730 mfg:CorporateAndInstitutionalCompanyMember us-gaap:OperatingSegmentsMember 2019-04-01 2020-03-31 0001335730 mfg:GlobalCorporateCompanyMember us-gaap:OperatingSegmentsMember 2019-04-01 2020-03-31 0001335730 mfg:GlobalMarketsCompanyMember us-gaap:OperatingSegmentsMember 2019-04-01 2020-03-31 0001335730 mfg:AssetManagementCompanyMember us-gaap:OperatingSegmentsMember 2019-04-01 2020-03-31 0001335730 us-gaap:IntersegmentEliminationMember 2019-04-01 2020-03-31 0001335730 mfg:AccumulatedOwnCreditRiskAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember 2019-04-01 2020-03-31 0001335730 us-gaap:AccumulatedDefinedBenefitPlansAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember 2019-04-01 2020-03-31 0001335730 us-gaap:AccumulatedNetInvestmentGainLossIncludingPortionAttributableToNoncontrollingInterestMember 2019-04-01 2020-03-31 0001335730 us-gaap:CommonStockMember 2019-04-01 2020-03-31 0001335730 us-gaap:AccumulatedOtherComprehensiveIncomeMember 2019-04-01 2020-03-31 0001335730 us-gaap:RetainedEarningsMember 2019-04-01 2020-03-31 0001335730 us-gaap:NoncontrollingInterestMember 2019-04-01 2020-03-31 0001335730 us-gaap:AccountingStandardsUpdate201409Member 2019-04-01 2020-03-31 0001335730 srt:MaximumMember 2019-04-01 2020-03-31 0001335730 srt:MinimumMember 2019-04-01 2020-03-31 0001335730 mfg:TradingSecuritiesMember 2019-04-01 2020-03-31 0001335730 us-gaap:GeneralAndAdministrativeExpenseMember 2019-04-01 2020-03-31 0001335730 us-gaap:OccupancyMember 2019-04-01 2020-03-31 0001335730 mfg:EntityWideSoftwareMember 2019-04-01 2020-03-31 0001335730 mfg:StockCompensationPlan1Member 2019-04-01 2020-03-31 0001335730 mfg:StockCompensationPlan2Member 2019-04-01 2020-03-31 0001335730 srt:AsiaMember 2019-04-01 2020-03-31 0001335730 srt:EuropeMember 2019-04-01 2020-03-31 0001335730 mfg:OthersCountriesMember 2019-04-01 2020-03-31 0001335730 country:US 2019-04-01 2020-03-31 0001335730 country:JP 2019-04-01 2020-03-31 0001335730 mfg:NonBankingSubsidiariesAndAffiliatedCompaniesMember srt:ParentCompanyMember 2019-04-01 2020-03-31 0001335730 mfg:BankingSubsidiaryMember srt:ParentCompanyMember 2019-04-01 2020-03-31 0001335730 srt:ParentCompanyMember 2019-04-01 2020-03-31 0001335730 us-gaap:EquityMethodInvesteeMember 2019-04-01 2020-03-31 0001335730 mfg:RetailAndBusinessBankingCompanyMember 2019-04-01 2020-03-31 0001335730 us-gaap:NetInvestmentHedgingMember 2019-04-01 2020-03-31 0001335730 us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMember 2021-04-01 2022-03-31 0001335730 mfg:PerformanceFinancialMarketValueAndOtherTypeGuaranteeMember 2021-04-01 2022-03-31 0001335730 mfg:SecuritiesRelatedBusinessMember 2021-04-01 2022-03-31 0001335730 mfg:DepositsRelatedBusinessMember 2021-04-01 2022-03-31 0001335730 mfg:LendingRelatedBusinessMember 2021-04-01 2022-03-31 0001335730 us-gaap:CorrespondentClearingMember 2021-04-01 2022-03-31 0001335730 us-gaap:InvestmentAdvisoryManagementAndAdministrativeServiceMember 2021-04-01 2022-03-31 0001335730 us-gaap:FiduciaryAndTrustMember 2021-04-01 2022-03-31 0001335730 mfg:AgencyBusinessMember 2021-04-01 2022-03-31 0001335730 mfg:GuaranteeRelatedBusinessMember 2021-04-01 2022-03-31 0001335730 us-gaap:FinancialServiceOtherMember 2021-04-01 2022-03-31 0001335730 us-gaap:FinancialServiceMember 2021-04-01 2022-03-31 0001335730 us-gaap:SecuritiesInvestmentMember 2021-04-01 2022-03-31 0001335730 us-gaap:NondesignatedMember 2021-04-01 2022-03-31 0001335730 us-gaap:DesignatedAsHedgingInstrumentMember us-gaap:NetInvestmentHedgingMember 2021-04-01 2022-03-31 0001335730 us-gaap:LongTermDebtMember 2021-04-01 2022-03-31 0001335730 us-gaap:ForeignExchangeMember 2021-04-01 2022-03-31 0001335730 us-gaap:LoansMember us-gaap:CreditRiskContractMember 2021-04-01 2022-03-31 0001335730 mfg:PeriodFiveMember 2021-04-01 2022-03-31 0001335730 us-gaap:PreferredStockMember 2021-04-01 2022-03-31 0001335730 mfg:FinancialInstrumentsHedgingForeignExchangeRiskMember 2021-04-01 2022-03-31 0001335730 mfg:AccumulatedOwnCreditRiskAdjustmentMember mfg:OtherNoninterestIncomeExpensesMember 2021-04-01 2022-03-31 0001335730 us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMember mfg:SalaryAndBenefitMember 2021-04-01 2022-03-31 0001335730 us-gaap:AccumulatedTranslationAdjustmentMember us-gaap:GainLossOnInvestmentsMember1 2021-04-01 2022-03-31 0001335730 us-gaap:AccumulatedNetUnrealizedInvestmentGainLossMember us-gaap:GainLossOnInvestmentsMember1 2021-04-01 2022-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:LargeCompaniesMember 2021-04-01 2022-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:CorporateRatingMember mfg:SmallAndMediumSizedCompaniesMember 2021-04-01 2022-03-31 0001335730 mfg:RetailRatingMember mfg:HousingLoanMember us-gaap:GeographicDistributionDomesticMember 2021-04-01 2022-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember mfg:RetailRatingMember mfg:OtherMember 2021-04-01 2022-03-31 0001335730 us-gaap:GeographicDistributionDomesticMember 2021-04-01 2022-03-31 0001335730 us-gaap:GeographicDistributionForeignMember 2021-04-01 2022-03-31 0001335730 mfg:PeriodFourMember 2021-04-01 2022-03-31 0001335730 mfg:TradingAccountGainsMember 2021-04-01 2022-03-31 0001335730 mfg:GlobalMarketsCompanyMember us-gaap:ExchangeTradedFundsMember 2021-04-01 2022-03-31 0001335730 us-gaap:ExchangeTradedFundsMember 2021-04-01 2022-03-31 0001335730 mfg:TradingSecuritiesMember 2021-04-01 2022-03-31 0001335730 us-gaap:AvailableforsaleSecuritiesMember 2021-04-01 2022-03-31 0001335730 us-gaap:AvailableforsaleSecuritiesMember mfg:NonJapaneseCorporateBondsMember 2021-04-01 2022-03-31 0001335730 us-gaap:ResidentialPortfolioSegmentMember 2021-04-01 2022-03-31 0001335730 us-gaap:CommercialPortfolioSegmentMember 2021-04-01 2022-03-31 0001335730 us-gaap:DebtSecuritiesMember 2021-04-01 2022-03-31 0001335730 us-gaap:EquitySecuritiesMember 2021-04-01 2022-03-31 0001335730 us-gaap:InterestRateContractMember 2021-04-01 2022-03-31 0001335730 us-gaap:ForeignExchangeContractMember 2021-04-01 2022-03-31 0001335730 us-gaap:EquityContractMember 2021-04-01 2022-03-31 0001335730 us-gaap:CreditRiskContractMember 2021-04-01 2022-03-31 0001335730 us-gaap:OtherContractMember 2021-04-01 2022-03-31 0001335730 us-gaap:SeniorDebtObligationsMember 2021-04-01 2022-03-31 0001335730 us-gaap:AccumulatedForeignCurrencyAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember 2021-04-01 2022-03-31 0001335730 us-gaap:TreasuryStockMember 2021-04-01 2022-03-31 0001335730 us-gaap:PropertyPlantAndEquipmentMember 2021-04-01 2022-03-31 0001335730 mfg:RetailAndBusinessBankingCompanyMember us-gaap:OperatingSegmentsMember 2021-04-01 2022-03-31 0001335730 mfg:CorporateAndInstitutionalCompanyMember us-gaap:OperatingSegmentsMember 2021-04-01 2022-03-31 0001335730 mfg:GlobalCorporateCompanyMember us-gaap:OperatingSegmentsMember 2021-04-01 2022-03-31 0001335730 mfg:GlobalMarketsCompanyMember us-gaap:OperatingSegmentsMember 2021-04-01 2022-03-31 0001335730 mfg:AssetManagementCompanyMember us-gaap:OperatingSegmentsMember 2021-04-01 2022-03-31 0001335730 us-gaap:IntersegmentEliminationMember 2021-04-01 2022-03-31 0001335730 mfg:AccumulatedOwnCreditRiskAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember 2021-04-01 2022-03-31 0001335730 us-gaap:AccumulatedDefinedBenefitPlansAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember 2021-04-01 2022-03-31 0001335730 us-gaap:AccumulatedNetInvestmentGainLossIncludingPortionAttributableToNoncontrollingInterestMember 2021-04-01 2022-03-31 0001335730 us-gaap:CommonStockMember 2021-04-01 2022-03-31 0001335730 us-gaap:AccumulatedOtherComprehensiveIncomeMember 2021-04-01 2022-03-31 0001335730 us-gaap:RetainedEarningsMember 2021-04-01 2022-03-31 0001335730 us-gaap:AvailableforsaleSecuritiesMember us-gaap:OtherThanSecuritiesInvestmentMember 2021-04-01 2022-03-31 0001335730 us-gaap:AvailableforsaleSecuritiesMember mfg:JapaneseCorporateBondsMember 2021-04-01 2022-03-31 0001335730 us-gaap:AvailableforsaleSecuritiesMember us-gaap:CommercialMortgageBackedSecuritiesMember 2021-04-01 2022-03-31 0001335730 us-gaap:DerivativeFinancialInstrumentsAssetsMember us-gaap:OtherContractMember 2021-04-01 2022-03-31 0001335730 us-gaap:DerivativeFinancialInstrumentsAssetsMember mfg:CreditRelatedContractsMember 2021-04-01 2022-03-31 0001335730 us-gaap:DerivativeFinancialInstrumentsAssetsMember us-gaap:EquityContractMember 2021-04-01 2022-03-31 0001335730 us-gaap:DerivativeFinancialInstrumentsAssetsMember us-gaap:ForeignExchangeContractMember 2021-04-01 2022-03-31 0001335730 us-gaap:DerivativeFinancialInstrumentsAssetsMember us-gaap:InterestRateContractMember 2021-04-01 2022-03-31 0001335730 mfg:TradingSecuritiesMember us-gaap:AllOtherCorporateBondsMember 2021-04-01 2022-03-31 0001335730 us-gaap:NoncontrollingInterestMember 2021-04-01 2022-03-31 0001335730 us-gaap:AvailableforsaleSecuritiesMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2021-04-01 2022-03-31 0001335730 mfg:TradingSecuritiesMember us-gaap:EquitySecuritiesMember 2021-04-01 2022-03-31 0001335730 mfg:TradingSecuritiesMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2021-04-01 2022-03-31 0001335730 us-gaap:AccountingStandardsUpdate201409Member 2021-04-01 2022-03-31 0001335730 dei:AdrMember 2021-04-01 2022-03-31 0001335730 us-gaap:CommonStockMember 2021-04-01 2022-03-31 0001335730 dei:BusinessContactMember 2021-04-01 2022-03-31 0001335730 mfg:PeriodEightMember 2021-04-01 2022-03-31 0001335730 mfg:PeriodSevenMember 2021-04-01 2022-03-31 0001335730 mfg:PeriodSixMember 2021-04-01 2022-03-31 0001335730 mfg:PeriodNineMember 2021-04-01 2022-03-31 0001335730 mfg:BaselIiiMember mfg:PeriodEightMember 2021-04-01 2022-03-31 0001335730 srt:MinimumMember 2021-04-01 2022-03-31 0001335730 srt:MaximumMember 2021-04-01 2022-03-31 0001335730 srt:MinimumMember us-gaap:BuildingMember 2021-04-01 2022-03-31 0001335730 srt:MaximumMember us-gaap:BuildingMember 2021-04-01 2022-03-31 0001335730 srt:MinimumMember us-gaap:FurnitureAndFixturesMember 2021-04-01 2022-03-31 0001335730 srt:MaximumMember us-gaap:FurnitureAndFixturesMember 2021-04-01 2022-03-31 0001335730 mfg:ImpairedLoansMember srt:MinimumMember 2021-04-01 2022-03-31 0001335730 us-gaap:SoftwareAndSoftwareDevelopmentCostsMember srt:MinimumMember 2021-04-01 2022-03-31 0001335730 us-gaap:SoftwareAndSoftwareDevelopmentCostsMember srt:MaximumMember 2021-04-01 2022-03-31 0001335730 us-gaap:CustomerRelationshipsMember mfg:ShinkoSecuritiesCompanyLimitedMember 2021-04-01 2022-03-31 0001335730 us-gaap:CustomerRelationshipsMember mfg:AssetManagementCompanyMember 2021-04-01 2022-03-31 0001335730 mfg:TradingSecuritiesMember 2021-04-01 2022-03-31 0001335730 us-gaap:GeneralAndAdministrativeExpenseMember 2021-04-01 2022-03-31 0001335730 us-gaap:OccupancyMember 2021-04-01 2022-03-31 0001335730 mfg:MizuhoFinancialGroupInc.Member country:JP 2021-04-01 2022-03-31 0001335730 mfg:MizuhoSecuritiesCompanyLimitedMember country:JP 2021-04-01 2022-03-31 0001335730 mfg:MhfgStockPlanMember 2021-04-01 2022-03-31 0001335730 mfg:StockCompensationPlan1Member 2021-04-01 2022-03-31 0001335730 mfg:StockCompensationPlan2Member 2021-04-01 2022-03-31 0001335730 mfg:StockCompensationPlan1Member us-gaap:PerformanceSharesMember 2021-04-01 2022-03-31 0001335730 mfg:StockCompensationPlan2Member us-gaap:PerformanceSharesMember 2021-04-01 2022-03-31 0001335730 mfg:MizuhoFinancialGroupIncMember 2021-04-01 2022-03-31 0001335730 mfg:UnitedStatesDollarDenominatedDebtMember mfg:SeniorBorrowingsAndDebtObligationsMember mfg:FixedRateDebtMember srt:MinimumMember 2021-04-01 2022-03-31 0001335730 mfg:OtherForeignCurrencyDenominatedDebtMember mfg:SeniorBorrowingsAndDebtObligationsMember mfg:FixedRateDebtMember srt:MinimumMember 2021-04-01 2022-03-31 0001335730 mfg:YenDenominatedNotesMember mfg:SeniorBorrowingsAndDebtObligationsMember mfg:FloatingRateDebtMember srt:MinimumMember 2021-04-01 2022-03-31 0001335730 mfg:UnitedStatesDollarDenominatedDebtMember mfg:SeniorBorrowingsAndDebtObligationsMember mfg:FloatingRateDebtMember srt:MinimumMember 2021-04-01 2022-03-31 0001335730 mfg:OtherForeignCurrencyDenominatedDebtMember mfg:SeniorBorrowingsAndDebtObligationsMember mfg:FloatingRateDebtMember srt:MinimumMember 2021-04-01 2022-03-31 0001335730 mfg:YenDenominatedNotesMember mfg:SubordinatedBorrowingsAndDebtObligationsMember mfg:FixedRateDebtMember srt:MinimumMember 2021-04-01 2022-03-31 0001335730 mfg:UnitedStatesDollarDenominatedDebtMember mfg:SubordinatedBorrowingsAndDebtObligationsMember mfg:FixedRateDebtMember srt:MinimumMember 2021-04-01 2022-03-31 0001335730 srt:MinimumMember mfg:SeniorBorrowingsAndDebtObligationsMember mfg:FixedRateDebtMember mfg:YenDenominatedNotesMember 2021-04-01 2022-03-31 0001335730 srt:MaximumMember mfg:SeniorBorrowingsAndDebtObligationsMember mfg:FixedRateDebtMember mfg:YenDenominatedNotesMember 2021-04-01 2022-03-31 0001335730 mfg:UnitedStatesDollarDenominatedDebtMember srt:MaximumMember mfg:SeniorBorrowingsAndDebtObligationsMember mfg:FixedRateDebtMember 2021-04-01 2022-03-31 0001335730 mfg:OtherForeignCurrencyDenominatedDebtMember srt:MaximumMember mfg:SeniorBorrowingsAndDebtObligationsMember mfg:FixedRateDebtMember 2021-04-01 2022-03-31 0001335730 mfg:YenDenominatedNotesMember srt:MaximumMember mfg:FloatingRateDebtMember mfg:SeniorBorrowingsAndDebtObligationsMember 2021-04-01 2022-03-31 0001335730 mfg:UnitedStatesDollarDenominatedDebtMember srt:MaximumMember mfg:FloatingRateDebtMember mfg:SeniorBorrowingsAndDebtObligationsMember 2021-04-01 2022-03-31 0001335730 mfg:OtherForeignCurrencyDenominatedDebtMember srt:MaximumMember mfg:FloatingRateDebtMember mfg:SeniorBorrowingsAndDebtObligationsMember 2021-04-01 2022-03-31 0001335730 mfg:UnitedStatesDollarDenominatedDebtMember mfg:FixedRateDebtMember mfg:SubordinatedBorrowingsAndDebtObligationsMember srt:MaximumMember 2021-04-01 2022-03-31 0001335730 srt:AsiaMember 2021-04-01 2022-03-31 0001335730 srt:EuropeMember 2021-04-01 2022-03-31 0001335730 mfg:OthersCountriesMember 2021-04-01 2022-03-31 0001335730 country:US 2021-04-01 2022-03-31 0001335730 country:JP 2021-04-01 2022-03-31 0001335730 mfg:NonBankingSubsidiariesAndAffiliatedCompaniesMember srt:ParentCompanyMember 2021-04-01 2022-03-31 0001335730 mfg:BankingSubsidiaryMember srt:ParentCompanyMember 2021-04-01 2022-03-31 0001335730 srt:ParentCompanyMember 2021-04-01 2022-03-31 0001335730 us-gaap:EquityMethodInvesteeMember 2021-04-01 2022-03-31 0001335730 mfg:EntityWideSoftwareMember 2021-04-01 2022-03-31 0001335730 mfg:DomesticDebtSecuritiesMember 2021-04-01 2022-03-31 0001335730 us-gaap:OtherLiabilitiesMember 2021-04-01 2022-03-31 0001335730 us-gaap:NetInvestmentHedgingMember 2021-04-01 2022-03-31 0001335730 us-gaap:NationalTaxAgencyJapanMember mfg:MizuhoFinancialGroupInc.Member 2021-04-01 2022-03-31 0001335730 mfg:ClassSixteenPreferredStockMember 2020-03-31 0001335730 mfg:ClassFifteenPreferredStockMember 2020-03-31 0001335730 mfg:ClassFourteenPreferredStockMember 2020-03-31 0001335730 srt:MaximumMember 2020-03-31 0001335730 srt:MinimumMember 2020-03-31 0001335730 country:JP 2020-03-31 0001335730 country:US 2020-03-31 0001335730 mfg:OthersCountriesMember 2020-03-31 0001335730 srt:EuropeMember 2020-03-31 0001335730 srt:AsiaMember 2020-03-31 0001335730 mfg:DomesticDebtSecuritiesMember 2021-04-01 0001335730 mfg:GovernmentBondsMember 2021-04-01 0001335730 mfg:GovernmentBondsMember 2022-04-01 0001335730 srt:CumulativeEffectPeriodOfAdoptionAdjustedBalanceMember 2020-03-31 0001335730 srt:CumulativeEffectPeriodOfAdoptionAdjustedBalanceMember us-gaap:ResidentialPortfolioSegmentMember 2020-03-31 0001335730 srt:CumulativeEffectPeriodOfAdoptionAdjustedBalanceMember us-gaap:CommercialPortfolioSegmentMember 2020-03-31 0001335730 srt:CumulativeEffectPeriodOfAdoptionAdjustmentMember 2020-03-31 0001335730 srt:CumulativeEffectPeriodOfAdoptionAdjustmentMember us-gaap:ResidentialPortfolioSegmentMember 2020-03-31 0001335730 srt:CumulativeEffectPeriodOfAdoptionAdjustmentMember us-gaap:CommercialPortfolioSegmentMember 2020-03-31 0001335730 us-gaap:ResidentialPortfolioSegmentMember 2020-03-31 0001335730 us-gaap:CommercialPortfolioSegmentMember 2020-03-31 0001335730 us-gaap:CommonStockMember 2020-03-31 0001335730 us-gaap:RetainedEarningsMember 2020-03-31 0001335730 srt:CumulativeEffectPeriodOfAdoptionAdjustedBalanceMember us-gaap:RetainedEarningsMember 2020-03-31 0001335730 us-gaap:AccumulatedOtherComprehensiveIncomeMember 2020-03-31 0001335730 us-gaap:TreasuryStockMember 2020-03-31 0001335730 us-gaap:NoncontrollingInterestMember 2020-03-31 0001335730 us-gaap:AccumulatedForeignCurrencyAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember 2020-03-31 0001335730 us-gaap:AccumulatedNetInvestmentGainLossIncludingPortionAttributableToNoncontrollingInterestMember 2020-03-31 0001335730 mfg:AccumulatedOwnCreditRiskAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember 2020-03-31 0001335730 us-gaap:AccumulatedDefinedBenefitPlansAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember 2020-03-31 0001335730 us-gaap:AccumulatedOtherComprehensiveIncomeMember srt:CumulativeEffectPeriodOfAdoptionAdjustedBalanceMember 2020-03-31 0001335730 us-gaap:AccumulatedForeignCurrencyAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember srt:CumulativeEffectPeriodOfAdoptionAdjustedBalanceMember 2020-03-31 0001335730 us-gaap:ResidentialPortfolioSegmentMember 2021-03-31 0001335730 us-gaap:CommercialPortfolioSegmentMember 2021-03-31 0001335730 us-gaap:AccumulatedForeignCurrencyAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember 2021-03-31 0001335730 us-gaap:AccumulatedOtherComprehensiveIncomeMember 2021-03-31 0001335730 mfg:AccumulatedOwnCreditRiskAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember 2021-03-31 0001335730 us-gaap:AccumulatedDefinedBenefitPlansAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember 2021-03-31 0001335730 us-gaap:AccumulatedNetInvestmentGainLossIncludingPortionAttributableToNoncontrollingInterestMember 2021-03-31 0001335730 mfg:TradingSecuritiesMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2020-03-31 0001335730 mfg:TradingSecuritiesMember us-gaap:AllOtherCorporateBondsMember 2020-03-31 0001335730 mfg:TradingSecuritiesMember us-gaap:EquitySecuritiesMember 2020-03-31 0001335730 us-gaap:DerivativeFinancialInstrumentsAssetsMember us-gaap:InterestRateContractMember 2020-03-31 0001335730 us-gaap:DerivativeFinancialInstrumentsAssetsMember us-gaap:ForeignExchangeContractMember 2020-03-31 0001335730 us-gaap:DerivativeFinancialInstrumentsAssetsMember us-gaap:EquityContractMember 2020-03-31 0001335730 us-gaap:DerivativeFinancialInstrumentsAssetsMember mfg:CreditRelatedContractsMember 2020-03-31 0001335730 us-gaap:DerivativeFinancialInstrumentsAssetsMember us-gaap:OtherContractMember 2020-03-31 0001335730 us-gaap:AvailableforsaleSecuritiesMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2020-03-31 0001335730 us-gaap:AvailableforsaleSecuritiesMember us-gaap:CommercialMortgageBackedSecuritiesMember 2020-03-31 0001335730 us-gaap:AvailableforsaleSecuritiesMember mfg:JapaneseCorporateBondsMember 2020-03-31 0001335730 us-gaap:AvailableforsaleSecuritiesMember us-gaap:OtherThanSecuritiesInvestmentMember 2020-03-31 0001335730 us-gaap:AvailableforsaleSecuritiesMember mfg:NonJapaneseCorporateBondsMember 2020-03-31 0001335730 mfg:TradingSecuritiesMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2021-03-31 0001335730 mfg:TradingSecuritiesMember us-gaap:AllOtherCorporateBondsMember 2021-03-31 0001335730 mfg:TradingSecuritiesMember us-gaap:EquitySecuritiesMember 2021-03-31 0001335730 us-gaap:DerivativeFinancialInstrumentsAssetsMember us-gaap:InterestRateContractMember 2021-03-31 0001335730 us-gaap:DerivativeFinancialInstrumentsAssetsMember us-gaap:ForeignExchangeContractMember 2021-03-31 0001335730 us-gaap:DerivativeFinancialInstrumentsAssetsMember us-gaap:EquityContractMember 2021-03-31 0001335730 us-gaap:DerivativeFinancialInstrumentsAssetsMember mfg:CreditRelatedContractsMember 2021-03-31 0001335730 us-gaap:AvailableforsaleSecuritiesMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2021-03-31 0001335730 us-gaap:CommercialMortgageBackedSecuritiesMember us-gaap:AvailableforsaleSecuritiesMember 2021-03-31 0001335730 us-gaap:AvailableforsaleSecuritiesMember us-gaap:OtherThanSecuritiesInvestmentMember 2021-03-31 0001335730 us-gaap:AvailableforsaleSecuritiesMember mfg:NonJapaneseCorporateBondsMember 2021-03-31 0001335730 us-gaap:AvailableforsaleSecuritiesMember mfg:JapaneseCorporateBondsMember 2021-03-31 0001335730 us-gaap:LongTermDebtMember 2020-03-31 0001335730 us-gaap:LongTermDebtMember 2021-03-31 0001335730 us-gaap:PerformanceSharesMember mfg:StockCompensationPlan2Member 2020-03-31 0001335730 mfg:StockCompensationPlan1Member us-gaap:PerformanceSharesMember 2020-03-31 0001335730 mfg:StockCompensationPlan1Member us-gaap:PerformanceSharesMember 2021-03-31 0001335730 us-gaap:PerformanceSharesMember mfg:StockCompensationPlan2Member 2021-03-31 0001335730 srt:ParentCompanyMember 2020-03-31 0001335730 us-gaap:NoncontrollingInterestMember 2021-03-31 0001335730 us-gaap:ParentMember 2021-03-31 0001335730 us-gaap:TreasuryStockMember 2021-03-31 0001335730 us-gaap:RetainedEarningsMember 2021-03-31 0001335730 us-gaap:CommonStockMember 2021-03-31 0001335730 us-gaap:ResidentialPortfolioSegmentMember 2019-03-31 0001335730 us-gaap:CommercialPortfolioSegmentMember 2019-03-31 0001335730 us-gaap:CommonStockMember 2019-03-31 0001335730 us-gaap:RetainedEarningsMember 2019-03-31 0001335730 srt:CumulativeEffectPeriodOfAdoptionAdjustedBalanceMember us-gaap:RetainedEarningsMember 2019-03-31 0001335730 us-gaap:AccumulatedOtherComprehensiveIncomeMember 2019-03-31 0001335730 srt:CumulativeEffectPeriodOfAdoptionAdjustedBalanceMember us-gaap:AccumulatedOtherComprehensiveIncomeMember 2019-03-31 0001335730 us-gaap:TreasuryStockMember 2019-03-31 0001335730 us-gaap:NoncontrollingInterestMember 2019-03-31 0001335730 us-gaap:AccumulatedForeignCurrencyAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember 2019-03-31 0001335730 us-gaap:AccumulatedNetInvestmentGainLossIncludingPortionAttributableToNoncontrollingInterestMember 2019-03-31 0001335730 mfg:AccumulatedOwnCreditRiskAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember 2019-03-31 0001335730 us-gaap:AccumulatedForeignCurrencyAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember srt:CumulativeEffectPeriodOfAdoptionAdjustedBalanceMember 2019-03-31 0001335730 us-gaap:AccumulatedDefinedBenefitPlansAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember 2019-03-31 0001335730 srt:ParentCompanyMember 2019-03-31 0001335730 us-gaap:ParentMember 2020-03-31 0001335730 srt:CumulativeEffectPeriodOfAdoptionAdjustedBalanceMember us-gaap:RetainedEarningsMember 2021-03-31 0001335730 srt:CumulativeEffectPeriodOfAdoptionAdjustedBalanceMember us-gaap:AccumulatedOtherComprehensiveIncomeMember 2021-03-31 0001335730 us-gaap:AccumulatedForeignCurrencyAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember srt:CumulativeEffectPeriodOfAdoptionAdjustedBalanceMember 2021-03-31 0001335730 us-gaap:ResidentialPortfolioSegmentMember 2022-03-31 0001335730 us-gaap:CommercialPortfolioSegmentMember 2022-03-31 0001335730 us-gaap:AccumulatedForeignCurrencyAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember 2022-03-31 0001335730 us-gaap:AccumulatedOtherComprehensiveIncomeMember 2022-03-31 0001335730 mfg:AccumulatedOwnCreditRiskAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember 2022-03-31 0001335730 us-gaap:AccumulatedDefinedBenefitPlansAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember 2022-03-31 0001335730 us-gaap:AccumulatedNetInvestmentGainLossIncludingPortionAttributableToNoncontrollingInterestMember 2022-03-31 0001335730 us-gaap:AvailableforsaleSecuritiesMember us-gaap:OtherThanSecuritiesInvestmentMember 2022-03-31 0001335730 us-gaap:AvailableforsaleSecuritiesMember mfg:NonJapaneseCorporateBondsMember 2022-03-31 0001335730 us-gaap:AvailableforsaleSecuritiesMember mfg:JapaneseCorporateBondsMember 2022-03-31 0001335730 us-gaap:AvailableforsaleSecuritiesMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2022-03-31 0001335730 us-gaap:DerivativeFinancialInstrumentsAssetsMember mfg:CreditRelatedContractsMember 2022-03-31 0001335730 us-gaap:DerivativeFinancialInstrumentsAssetsMember us-gaap:EquityContractMember 2022-03-31 0001335730 us-gaap:DerivativeFinancialInstrumentsAssetsMember us-gaap:ForeignExchangeContractMember 2022-03-31 0001335730 us-gaap:DerivativeFinancialInstrumentsAssetsMember us-gaap:InterestRateContractMember 2022-03-31 0001335730 mfg:TradingSecuritiesMember us-gaap:EquitySecuritiesMember 2022-03-31 0001335730 mfg:TradingSecuritiesMember us-gaap:AllOtherCorporateBondsMember 2022-03-31 0001335730 mfg:TradingSecuritiesMember us-gaap:ResidentialMortgageBackedSecuritiesMember 2022-03-31 0001335730 us-gaap:LongTermDebtMember 2022-03-31 0001335730 mfg:StockCompensationPlan1Member us-gaap:PerformanceSharesMember 2022-03-31 0001335730 us-gaap:PerformanceSharesMember mfg:StockCompensationPlan2Member 2022-03-31 0001335730 us-gaap:NoncontrollingInterestMember 2022-03-31 0001335730 us-gaap:ParentMember 2022-03-31 0001335730 us-gaap:TreasuryStockMember 2022-03-31 0001335730 us-gaap:RetainedEarningsMember 2022-03-31 0001335730 us-gaap:CommonStockMember 2022-03-31 iso4217:JPY xbrli:shares xbrli:pure utr:Year utr:Day utr:Month mfg:Segment iso4217:JPY xbrli:shares mfg:Loans