Mizuho Financial (MFG) 6-K 28 Dec 20 2020 Q2 Current report (foreign) Financial data

Cover Page

Cover Page	6 Months Ended
	Sep. 30, 2020
Document Information [Line Items]
Document Type	6-K
Amendment Flag	false
Document Period End Date	Sep. 30, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Entity Registrant Name	MIZUHO FINANCIAL GROUP INC
Entity Central Index Key	0001335730
Current Fiscal Year End Date	--03-31

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - JPY (¥) ¥ in Millions		Sep. 30, 2020	Mar. 31, 2020
Assets:
Cash and due from banks		¥ 1,648,974	¥ 2,325,139
Interest-bearing deposits in other banks		41,588,074	39,625,975
Call loans and funds sold		534,345	1,006,991
Receivables under resale agreements		12,666,088	18,580,919
Receivables under securities borrowing transactions		2,185,575	2,216,059
Trading account assets		29,467,045	28,092,871
Investments (Note 3):
Available-for-sale securities (including assets pledged that secured parties are permitted to sell or repledge of ¥1,036,534 million at March 31, 2020 and ¥1,542,200 million at September 30, 2020), net of allowance		26,546,800	19,112,952
Held-to-maturity securities (including assets pledged that secured parties are permitted to sell or repledge of ¥297,240 million at March 31, 2020 and ¥308,448 million at September 30, 2020)	[1],[2]	789,978	862,031
Equity securities (including assets pledged that secured parties are permitted to sell or repledge of ¥92,806 million at September 30,2020)		3,501,678	3,256,717
Other investments		467,963	443,951
Loans (Notes 4 and 5)		90,475,747	87,528,088
Allowance for credit losses on loans		(622,526)	(440,855)
Loans, net of allowance		89,853,221	87,087,233
Premises and equipment—net		1,800,234	1,856,248
Due from customers on acceptances		181,435	167,764
Accrued income		284,667	323,632
Goodwill		92,695	92,997
Intangible assets		60,377	64,689
Deferred tax assets		61,233	136,713
Other assets (Note 6)		5,864,238	5,965,879
Total assets		217,594,620	211,218,760
Liabilities and equity:
Noninterest-bearing deposits		28,974,310	28,109,943
Interest-bearing deposits		90,386,518	86,651,036
Noninterest-bearing deposits		1,960,284	2,186,203
Interest-bearing deposits		27,946,322	28,001,485
Due to trust accounts		563,543	249,737
Call money and funds purchased		1,903,686	2,263,076
Payables under repurchase agreements (Note 19)		19,326,143	17,970,662
Payables under securities lending transactions (Note 19)		1,475,850	1,423,638
Other short-term borrowings		7,526,025	4,914,485
Trading account liabilities		10,590,312	12,416,785
Bank acceptances outstanding		181,435	167,764
Income taxes payable		55,659	68,557
Deferred tax liabilities		36,967	25,874
Accrued expenses		178,849	249,344
Long-term debt		11,049,044	10,346,152
Other liabilities (Note 6)		6,299,620	6,998,395
Total		208,454,567	202,043,136
Commitments and contingencies (Note 14)
MHFG shareholders' equity:
Common stock (Note 7)-no par value, authorized 4,800,000,000 shares at March 31, 2020 and September 30, 2020, and issued 2,539,249,894 shares at March 31, 2020 and September 30, 2020		5,826,427	5,827,500
Retained earnings		2,796,736	2,700,774
Accumulated other comprehensive income(loss), net of tax (Note 8)		133,837	(9,494)
Less: Treasury stock, at cost-Common stock 3,210,681 shares at March 31, 2020, and 3,868,308 shares at September 30, 2020		(7,024)	(6,415)
Total MHFG shareholders' equity		8,749,976	8,512,365
Noncontrolling interests		390,077	663,259
Total equity		9,140,053	9,175,624
Total liabilities and equity		217,594,620	211,218,760
Consolidated VIEs
Assets:
Cash and due from banks		1,592	8,749
Interest-bearing deposits in other banks		74,205	61,439
Call loans and funds sold		291,078	422,304
Trading account assets		2,386,317	2,438,607
Investments (Note 3):
Investments		80,226	62,262
Loans, net of allowance		7,682,432	2,285,831
Other assets (Note 6)		519,169	535,954
Total assets		11,035,019	5,815,146
Liabilities and equity:
Payables under securities lending transactions (Note 19)		57,257	138,094
Other short-term borrowings		43,440	60,086
Trading account liabilities		24,317	34,205
Long-term debt		540,123	330,863
Other liabilities (Note 6)		911,992	948,715
Total		¥ 1,577,129	¥ 1,511,963
[1]	Accrued interest receivables are excluded from amortized cost, of which the amount was ¥4,153 million at September 30, 2020 and included in Accrued income.
[2]	Amortized cost, net of the allowance for credit losses, of which the amounts related to available-for-sale securities was ¥7,551 million at September 30, 2020.

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - JPY (¥) ¥ in Millions	Sep. 30, 2020	Mar. 31, 2020
Trading account assets, assets pledged that secured parties are permitted to sell or repledge	¥ 7,696,203	¥ 4,978,497
Available-for-sale securities, assets pledged that secured parties are permitted to sell or repledge	1,542,200	1,036,534
Held-to-maturity securities, assets pledged that secured parties are permitted to sell or repledge	308,448	297,240
Long-term debt, liabilities accounted for at fair value	¥ 2,802,428	¥ 2,537,082
Common stock, par value	¥ 0	¥ 0
Common stock, authorized	4,800,000,000	4,800,000,000
Common stock, issued	2,539,249,894	2,539,249,894
Treasury stock, shares	3,868,308	3,210,681
Equity securities, assets pledged that secured parties are permitted to sell or repledge	¥ 92,806

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME - JPY (¥) ¥ in Millions		6 Months Ended
		Sep. 30, 2020	Sep. 30, 2019
Interest and dividend income:
Loans, including fees		¥ 541,675	¥ 719,443
Investments:
Interest		31,236	52,249
Dividends		24,875	36,109
Trading account assets		127,785	108,881
Call loans and funds sold		1,270	2,963
Receivables under resale agreements and securities borrowing transactions		22,894	150,728
Deposits in other banks		22,111	56,981
Total interest and dividend income		771,846	1,127,354
Interest expense:
Deposits		110,839	335,290
Trading account liabilities		28,208	28,794
Call money and funds purchased		1,282	4,771
Payables under repurchase agreements and securities lending transactions		33,267	197,410
Other short-term borrowings		11,988	15,855
Long-term debt		85,593	98,502
Total interest expense		271,177	680,622
Net interest income		500,669	446,732
Provision (credit) for credit losses (Notes 3 and 5)		60,633	13,773
Net interest income after provision (credit) for credit losses		440,036	432,959
Noninterest income (Note 16):
Fee and commission income		428,317	403,992
Foreign exchange gains (losses)—net	[1]	22,785	27,923
Trading account gains (losses)—net	[2]	257,591	395,405
Investment gains (losses)—net:
Debt securities	[1]	46	31,092
Equity securities	[1]	266,119	(126,648)
Equity in earnings (losses) of equity method investees—net	[1]	5,788	22,066
Gains on disposal of premises and equipment	[1]	6,849	1,693
Other noninterest income	[2],[3]	23,715	34,839
Total noninterest income		1,011,210	790,362
Noninterest expenses:
Salaries and employee benefits		346,150	334,041
General and administrative expenses		299,350	314,840
Occupancy expenses		93,314	103,693
Fee and commission expenses		93,016	101,175
Provision (credit) for credit losses on off-balance-sheet instruments		(7,391)	(8,248)
Other noninterest expenses		78,966	67,364
Total noninterest expenses		903,405	912,865
Income before income tax expense		547,841	310,456
Income tax expense (Note 11)		137,761	83,120
Net income	[4]	410,080	227,336
Less: Net income attributable to noncontrolling interests		94,194	14,352
Net income attributable to MHFG shareholders		¥ 315,886	¥ 212,984
Earnings per common share (Note 10):
Basic net income per common share		¥ 124.50	¥ 83.96
Diluted net income per common share	[5]	124.49	83.95
Dividends per common share		¥ 37.50	¥ 37.50
[1]	These amounts are revenues from contracts that do not meet the scope of ASC 606.
[2]	Part of these amounts are considered to be revenues from contracts that are within the scope of ASC 606.
[3]	These amounts include the net unrealized gains resulting from changes in fair values of structured notes that contain embedded derivatives. See Note 17 “Fair value” for further details.
[4]	The amounts that have been reclassified out of Accumulated other comprehensive income (loss), net of tax into net income are presented in Note 8 “Accumulated other comprehensive income (loss), net of tax”.
[5]	For the six months ended September 30, 2020, 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.

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - JPY (¥) ¥ in Millions		6 Months Ended
		Sep. 30, 2020	Sep. 30, 2019
Net income	[1]	¥ 410,080	¥ 227,336
Other comprehensive income (loss), net of tax		142,550	(56,583)
Total comprehensive income		552,630	170,753
Less: Total comprehensive income attributable to noncontrolling interests		93,413	14,023
Total comprehensive income attributable to MHFG shareholders		¥ 459,217	¥ 156,730
[1]	The amounts that have been reclassified out of Accumulated other comprehensive income (loss), net of tax into net income are presented in Note 8 “Accumulated other comprehensive income (loss), net of tax”.

CONSOLIDATED STATEMENTS OF EQUI

CONSOLIDATED STATEMENTS OF EQUITY - JPY (¥) ¥ in Millions	Total	Common Stock	Retained Earnings	Retained EarningsCumulative effect of change in accounting principles	Retained EarningsCumulative effect, period of adoption, adjusted balance	Accumulated other comprehensive income (loss)	Accumulated other comprehensive income (loss)Cumulative effect of change in accounting principles		Accumulated other comprehensive income (loss)Cumulative effect, period of adoption, adjusted balance	Treasury Stock	Parent	Noncontrolling Interest
Balance at beginning of period at Mar. 31, 2019		¥ 5,829,657	¥ 2,740,545	¥ 1,052	¥ 2,741,597	¥ 164,021	¥ (1,052)	[1]	¥ 162,969	¥ (7,704)		¥ 774,974
Purchases of treasury stock										(1,851)
Performance-based stock compensation program		(806)
Disposal of treasury stock										2,745
Net income attributable to MHFG shareholders	¥ 212,984		212,984
Change during period	(56,583)					(56,254)
Other		(896)	(611)
Transactions between the MHFG Group and the noncontrolling interest shareholders												(79,439)
Dividends paid to noncontrolling interests												(9,618)
Dividends declared			(95,197)
Net income attributable to noncontrolling interests	(14,352)											14,352
Other												(329)
Balance at end of fiscal year at Sep. 30, 2019	9,486,573	5,827,955	2,858,773			106,715				(6,810)	¥ 8,786,633	699,940
Balance at beginning of period at Mar. 31, 2020	9,175,624	5,827,500	2,700,774	¥ (124,636)	¥ 2,576,138	(9,494)	¥ 0		¥ (9,494)	(6,415)		663,259
Purchases of treasury stock										(1,995)
Performance-based stock compensation program		(553)
Disposal of treasury stock										1,386
Net income attributable to MHFG shareholders	315,886		315,886
Change during period	142,550					143,331
Other		(520)	(80)
Transactions between the MHFG Group and the noncontrolling interest shareholders												(356,311)
Dividends paid to noncontrolling interests												(10,284)
Dividends declared			(95,208)
Net income attributable to noncontrolling interests	(94,194)											94,194
Other												(781)
Balance at end of fiscal year at Sep. 30, 2020	¥ 9,140,053	¥ 5,826,427	¥ 2,796,736			¥ 133,837				¥ (7,024)	¥ 8,749,976	¥ 390,077
[1]	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.

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - JPY (¥) ¥ in Millions		6 Months Ended
		Sep. 30, 2020	Sep. 30, 2019
Cash flows from operating activities:
Net income	[1]	¥ 410,080	¥ 227,336
Less: Net income attributable to noncontrolling interests		94,194	14,352
Net income attributable to MHFG shareholders		315,886	212,984
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization		115,614	120,369
Provision (credit) for credit losses		60,633	13,773
Investment losses (gains)—net		(266,165)	95,556
Equity in losses (earnings) of equity method investees—net	[2]	(5,788)	(22,066)
Foreign exchange losses (gains)—net		(92,865)	(172,215)
Deferred income tax expense (benefit)		57,807	(5,317)
Net change in trading account assets		(1,784,129)	(3,753,226)
Net change in trading account liabilities		(1,874,766)	2,138,290
Net change in loans held for sale		18,781	17,427
Net change in accrued income		34,404	24,548
Net change in accrued expenses		(80,875)	(5,248)
Other—net		(159,507)	122,946
Net cash used in operating activities		(3,660,970)	(1,212,179)
Cash flows from investing activities:
Proceeds from sales of Available-for-sale securities		13,363,620	15,661,178
Proceeds from sales of Equity securities	[3]	1,413,300	1,177,962
Proceeds from maturities of Available-for-sale securities		12,719,308	8,454,526
Proceeds from maturities of Held-to-maturity securities		60,947	525,912
Purchases of Available-for-sale securities		(33,753,387)	(24,330,083)
Purchases of Equity securities	[3]	(1,383,195)	(1,209,953)
Proceeds from sales of loans		832,515	878,108
Net change in loans		(3,944,882)	(3,054,528)
Net change in call loans and funds sold, and receivables under resale agreements and securities borrowing transactions		6,141,641	(2,127,069)
Proceeds from sales of premises and equipment		12,856	8,748
Purchases of premises and equipment		(73,768)	(81,427)
Proceeds from sales of investments in subsidiaries (affecting the scope of consolidation)		25,190
Net cash used in investing activities		(4,585,855)	(4,096,626)
Cash flows from financing activities:
Net change in deposits		4,513,597	2,848,039
Net change in call money and funds purchased, and payables under repurchase agreements and securities lending transactions		1,490,083	2,549,230
Net change in due to trust accounts		313,806	7,619
Net change in other short-term borrowings		2,628,438	(358,650)
Proceeds from issuance of long-term debt		1,270,809	1,223,618
Repayment of long-term debt		(515,802)	(2,195,976)
Proceeds from noncontrolling interests		73,688	33,009
Payments to noncontrolling interests		(3,859)	(105,424)
Proceeds from sales of treasury stock		839	1,515
Purchases of treasury stock		(1,503)	(1,436)
Purchases of treasury stock of subsidiaries		(5,414)
Dividends paid		(95,242)	(95,165)
Dividends paid to noncontrolling interests		(10,284)	(9,618)
Net cash provided by financing activities		9,659,156	3,896,761
Effect of exchange rate changes on cash and cash equivalents		(126,397)	(279,689)
Net increase (decrease) in cash and cash equivalents	[4]	1,285,934	(1,691,733)
Cash and cash equivalents at beginning of period	[4]	41,951,114	45,672,739
Cash and cash equivalents at end of period	[4]	43,237,048	43,981,006
Noncash investing activities:
Transfer of loans into loans held-for-sale		¥ 11,399	¥ 64,996
[1]	The amounts that have been reclassified out of Accumulated other comprehensive income (loss), net of tax into net income are presented in Note 8 “Accumulated other comprehensive income (loss), net of tax”.
[2]	These amounts are revenues from contracts that do not meet the scope of ASC 606.
[3]	Proceeds from sales of Equity securities as well as Purchases of Equity securities include cash activity related to Other investments for the six months ended September 30 2019 and 2020, the amounts of which are not significant.
[4]	Cash and cash equivalents consists of Cash and due from banks and Interest-bearing deposits in other banks. Cash deposited with central banks that must be maintained to meet minimum regulatory requirements is classified as restricted cash and included in Cash and cash equivalents.

Basis of presentation

Basis of presentation	6 Months Ended
	Sep. 30, 2020
Basis of presentation	1. Basis of presentation Mizuho Financial Group, Inc. (“MHFG”) is a joint stock corporation with limited liability under the laws of Japan. MHFG is a holding company for Mizuho Bank, Ltd. (“MHBK”), Mizuho Trust & Banking Co., Ltd. (“MHTB”), Mizuho Securities Co., Ltd. (“MHSC”), Asset Management One Co., Ltd. (“Asset Management One”), and other subsidiaries. MHFG, through its subsidiaries (“the MHFG Group,” or “the Group”), provides domestic and international financial services in Japan and other countries. For a discussion of the Group’s segment information, see Note 20 “Business segment information.” MHFG and its domestic subsidiaries as well as its foreign subsidiaries maintain their accounting records in accordance with the accounting standards of Japan and those standards of the countries in which they are domiciled. Certain adjustments and reclassifications have been incorporated in the accompanying consolidated financial statements to conform them to the accounting principles generally accepted in the United States of America (“U.S. GAAP”). The consolidated financial statements are stated in Japanese yen, the currency of the country in which MHFG is incorporated and principally operates. The accompanying consolidated financial statements include the accounts of MHFG and its subsidiaries. MHFG’s interim financial reporting period ends on September 30. Certain of MHFG’s subsidiaries have different interim financial reporting periods than September 30. For those subsidiaries with interim financial reporting periods within three months of MHFG’s interim financial reporting period, the effect of intervening events that materially affect the financial position or results of operations through the date of each of the periods presented in the MHFG’s consolidated financial statements have been considered for adjustment and/or disclosure. When determining whether to consolidate investee entities, the MHFG Group performs an analysis of the facts and circumstances of the particular relationships between the MHFG Group and the investee entities as well as the ownership of voting shares. The consolidated financial statements also include the accounts of VIEs for which MHFG or its subsidiaries have been determined to be the primary beneficiary in accordance with the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) 810, “Consolidation” (“ASC 810”). All significant intercompany transactions and balances have been eliminated upon consolidation. The MHFG Group accounts for investments in entities over which it has significant influence by using the equity method of accounting. These investments are included in Other investments and the Group’s proportionate share of income or loss is included in Equity in earnings (losses) of equity method investees-net. On June 25, 2020, a 1-for-10 share consolidation was approved at the Ordinary General Meeting of Shareholders and it became effective on October 1, 2020. All share and per share information with respect to MHFG’s common stock and preferred stock have been restated to reflect the effect of the share consolidation and related amendments to the articles of incorporation for all periods presented. See Equity on the consolidated balance sheets, Earnings per common share and Dividends per share on the consolidated statements of income, Note 7 “Preferred and common stock,” and Note 10 “Earnings per common share” for the restated figures. In addition, certain other comparative amounts for the prior period have been reclassified in order to conform to the current period’s presentation. The unaudited consolidated financial statements should be read in conjunction with the audited financial statements and related notes thereto included in the annual financial statements for the fiscal year ended March 31, 2020. Certain financial information that is normally included in annual financial statements prepared in accordance with U.S. GAAP, but is not required for interim reporting purposes, has been condensed or omitted. Use of estimates The preparation of the consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect reported amounts and related disclosures. Specific areas, among others, requiring the application of management’s estimates and judgment include assumptions pertaining to the allowance for credit losses, valuation of deferred tax assets, valuation of derivative financial instruments, valuation of investments and valuation of pension and other employee benefits. During times of pandemics and dislocated markets, such as COVID-19, Financial instruments—current expected credit losses (“CECL”) The adoption of this guidance established a single allowance framework for all financial assets measured at amortized cost and certain off-balance-sheet instrument exposures. This framework requires management’s estimate to reflect credit losses over the instrument’s remaining expected lives and consider expected future changes in macroeconomic conditions. The following note and Note 2 “Issued accounting pronouncements,” Note 3 “Investments,” Note 4 “Loans” and Note 5 “Allowance for credit losses on loans” provide further information about the impact that the adoption of ASC 326, “Financial Instruments - Credit Losses” (“ASC 326”) had on the MHFG Group. Allowance for credit losses on loans Effective April 1, 2020, the allowance for credit losses on loans is established for current expected credit losses on the MHFG Group’s loan portfolio in accordance with ASC 326. Prior to April 1, 2020, the allowance for credit losses on loans was established based on an incurred loss model in accordance with ASC 310, “Receivables” (“ASC 310”) and ASC 450, “Contingencies” (“ASC 450”). The MHFG Group makes adjustments to the allowance for credit losses on loans through Provision (credit) for credit losses in the consolidated statements of income in each subsequent reporting period. Loan principal that management judges to be uncollectible, based on detailed loan reviews and a credit quality assessment, is charged off against the allowance for credit losses on loans. In general, the Group charges off loans when the Group determines that the obligor should be classified as substantially bankrupt or bankrupt. See Note 4 “Loans” for the definitions of obligor categories. Obligors in the retail portfolio segment are generally determined to be substantially bankrupt when they are past due for more than six months, and as for obligors in the corporate portfolio segment, the Group separately monitors the credit quality of each obligor without using time-based triggers. The Group does not record expected credit losses for accrued interest receivables because uncollectible accrued interest is reversed through interest income in a timely manner in line with the Group’s nonaccrual and past due policies for loans. The MHFG Group maintains an appropriate allowance for credit losses on loans to represent management’s estimate of the expected credit losses in the Group’s loan portfolio. The management evaluates the appropriateness of the allowance for credit losses on loans semi-annually. The allowance considers expected credit losses over the remaining expected lives of the applicable instruments. The expected life of each instrument is determined by considering expected prepayments, contractual terms and cancellation features. When determining expected credit losses, a single forward-looking macroeconomic scenario is considered over a reasonable and supportable forecast period. This forward-looking macroeconomic scenario is based on the Group’s stress testing and in line with the scenario used for the Group’s business plan. If the scenario does not reflect a sudden change in economic conditions adequately, it could be possible to make adjustments to the scenario. After the forecast period, the Group reverts to long-term historical loss experience with a certain graduated transition period, to estimate losses over the remaining lives. The macroeconomic scenario is updated at least semi-annually and is reviewed accordingly to reflect current economic conditions and the Group’s expectation of future conditions on a timely basis. For April 1, 2020 and September 30, 2020, the Group used the most recent macroeconomic scenario available during the Group’s credit loss estimation process. In terms of the internal risk ratings, for the corporate portfolio segment, the credit quality review process and the credit rating process serve as the basis for determining the allowance for credit losses on loans. Through such processes loans are categorized into groups to reflect the probability of default, whereby the MHFG Group’s management assesses the ability of borrowers to service their debt, taking into consideration current financial information, ability to generate cash, historical payment experience, analysis of relevant industry segments and current trends. For the retail portfolio segment, the different categories of past due status of loans are primarily utilized in the credit quality review and the credit rating processes as the basis for determining the allowance for credit losses on loans. In general, the MHFG Group estimates expected credit losses collectively on the loans in the case of normal and watch obligors, considering the risk associated with a particular pool and the probability that the exposures within the pool will deteriorate or default. The allowance for credit losses on nonaccrual loans includes the allowance for groups of loans which were collectively evaluated for expected credit losses, in addition to the allowance for those loans that were individually evaluated for expected credit losses. See The estimation of expected credit losses that are evaluated collectively begins with a quantitative calculation that considers the likelihood of the borrower changing delinquency status or moving from one obligor category or rating to another. The quantitative calculation covers expected credit losses over an instrument’s expected life and is estimated by applying credit loss factors to the MHFG Group’s estimated exposure at default. The credit loss factors incorporate the probability of default as well as the loss given default based on the historical loss rates and the external ratings such as S&P. The model and inputs used to determine credit losses on loans that are evaluated collectively are analyzed on a periodic basis by comparing the estimated values with the actual results subsequent to the balance sheet date. The MHFG Group divides its overall portfolio into domestic and foreign portfolios, and categorizes the domestic portfolio into four portfolio segments according to their risk profiles: corporate, retail, sovereign, and banks and financial institutions. The corporate portfolio segment consists of loans originated primarily by MHBK and MHTB, and includes mainly business loans such as those used for working capital and capital expenditure, as well as loans for which the primary source of repayment of the obligation is income generated by the relevant assets such as project finance, asset finance and real estate finance. The corporate portfolio segment is divided into two classes based on their risk characteristics: large companies, and small and medium-sized The retail portfolio segment consists mainly of residential mortgage loans originated by MHBK, and it is divided into two classes based on their risk characteristics: housing loan and others. For the retail portfolio segment, the Japanese unemployment rate is applied as a key factor. As it pertains to troubled debt restructuring (“TDR”) loans in the retail portfolio segment, which are subject to collective evaluation for expected credit losses, the restructuring itself, as well as subsequent payment defaults, if any, are considered in determining obligor categories. Expected credit loss estimates also include consideration of expected cash recoveries on loans previously charged-off, or expected recoveries on collateral dependent loans where recovery is expected through sale of the collateral. The allowance recorded for individually evaluated loans is based on (1) the present value of expected future cash flows, after considering the restructuring effect and subsequent payment default with respect to TDRs, discounted at the loan’s initial effective interest rate, or (2) the loan’s observable market price, or (3) the fair value of the collateral if the loan is collateral dependent. The collateral that the MHFG Group obtains for loans consists primarily of real estate. In obtaining the collateral, the Group evaluates the fair value of the collateral and its legal enforceability. The Group also performs subsequent re-evaluations at least once a year. As it pertains to real estate collateral, valuation is generally performed by an appraising subsidiary which is independent from the Group’s loan origination departments by using generally accepted valuation techniques such as (1) the replacement cost approach, (2) the sales comparison approach or (3) the income approach. In the case of large real estate collateral, the Group generally engages third-party appraisers to perform the valuation. The MHFG Group’s methodology for determining the appropriate allowance for credit losses on loans also considers the imprecision inherent in the methodologies used. As a result, the amounts determined under the methodologies described above could be adjusted by management to consider the potential impact of other qualitative factors which include, but are not limited to , Allowance for credit losses on off-balance-sheet The MHFG Group maintains the allowance for credit losses on off-balance-sheet off-balance-sheet off-balance-sheet Allowance for credit losses on available-for-sale The MHFG Group performs periodic reviews to identify impaired securities in accordance with ASC 326. Available-for-sale securities are impaired if the fair value is less than the amortized cost (excluding accrued interest receivable). For available-for-sale available-for-sale available-for-sale is recognized immediately through earnings. In other cases, the Group evaluates expected cash flows to be received and determines if a credit loss exists, and if so, the amount of the credit loss is recognized in Provision (credit) for credit losses, while the remaining decline in fair value is recognized in other comprehensive income, net of applicable taxes. The Group generally does not record an allowance for credit losses for accrued interest receivables related to available-for-sale securities because these receivables are reversed through interest income, consistent with the Group’s past due policies. For additional information, see Note 4 “Loans.” Before the adoption of ASC 326, the previous other-than-temporary impairment model was applied for available-for-sale

Issued accounting pronouncement

Issued accounting pronouncements	6 Months Ended
	Sep. 30, 2020
Issued accounting pronouncements	2. Issued accounting pronouncements Adopted accounting pronouncements In June 2016, the FASB issued ASU No.2016-13, No.2016-13”). No.2019-04, No.2019-04”). No.2019-05, No.2019-05”). No.2019-11, No.2019-11”). No.2016-13, available-for-sale No.2016-13, 2019-04, 2019-05, 2019-11 allowance COVID-19. available-for-sale The following table reconciles the closing allowance for loans and off-balance-sheet the opening allowance determined with ASC 326 at April 1, 2020: At March 31, 2020 ASC 310/450 Transition Adjustment At April 1, 2020 ASC 326 (in billions of yen) Loans: Corporate 413 78 491 Retail 28 78 106 Off-balance-sheet 46 20 66 For additional information, see Note 3 “Investments,” Note 4 “Loans” and Note 5 “Allowance for credit losses on loans.” In August 2018, the FASB issued ASU No.2018-13, “Fair Value Measurement (Topic 820)—Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement” (“ASU No.2018-13”). The ASU modifies the disclosure requirements for fair value measurements in order to improve the effectiveness of the notes to financial statements. The amendments require additional disclosure on changes in unrealized gains and losses, the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements, and the narrative description of measurement uncertainty. The MHFG Group adopted ASU No.2018-13 on April 1, 2020. Certain of the requirements are applied prospectively, and other amendments are applied retrospectively. The adoption of ASU No.2018-13 did not have a material impact on disclosures in the Group’s consolidated financial statements. In August 2018, the FASB issued ASU No.2018-14, 715-20)—Disclosure No.2018-14”). No.2018-14 No.2018-14 In October 2018, the FASB issued ASU No.2018-17, No.2018-17”). No.2018-17 No.2018-17 In March 2020, the FASB issued ASU No.2020-04, No.2020-04”).

Investments

Investments	6 Months Ended
	Sep. 30, 2020
Investments	3. Investments Available-for-sale held-to-maturity The amortized cost, net of allowance for credit losses, gross unrealized gains and losses, and fair value of available-for-sale and held-to-maturity securities at March 31, 2020 and September 30, 2020 are as follows: Amortized (5)(6) Gross unrealized gains Gross unrealized losses Fair value (in millions of yen) March 31, 2020 Available-for-sale Debt securities: Japanese government bonds 12,651,677 1,319 50,224 12,602,772 Japanese local government bonds 272,412 649 494 272,567 U.S. Treasury bonds and federal agency securities 927,172 7,733 — 934,905 Other foreign government bonds 1,408,009 3,273 202 1,411,080 Agency mortgage-backed securities (1) 494,958 10,490 434 505,014 Residential mortgage-backed securities 83,077 1,405 151 84,331 Commercial mortgage-backed securities 609,559 5,551 106 615,004 Japanese corporate bonds and other debt securities (2) 1,836,540 7,489 8,772 1,835,257 Foreign corporate bonds and other debt securities (3) 849,595 2,595 168 852,022 Total 19,132,999 40,504 60,551 19,112,952 Held-to-maturity Debt securities: Japanese government bonds 479,936 13,357 — 493,293 Agency mortgage-backed securities (4) 382,095 1,245 1,303 382,037 Total 862,031 14,602 1,303 875,330 September 30, 2020 Available-for-sale Debt securities: Japanese government bonds 19,964,553 1,084 45,274 19,920,363 Japanese local government bonds 406,873 757 446 407,184 U.S. Treasury bonds and federal agency securities 625,398 1,388 2 626,784 Other foreign government bonds 1,353,376 3,020 74 1,356,322 Agency mortgage-backed securities (1) 509,808 10,650 433 520,025 Residential mortgage-backed securities 78,883 1,220 123 79,980 Commercial mortgage-backed securities 634,537 6,674 69 641,142 Japanese corporate bonds and other debt securities (2) 2,066,234 12,579 8,785 2,070,028 Foreign corporate bonds and other debt securities (3) 922,752 3,410 1,190 924,972 Total 26,562,414 40,782 56,396 26,546,800 Held-to-maturity Debt securities: Japanese government bonds 479,947 11,505 — 491,452 Agency mortgage-backed securities (4) 310,031 10,666 — 320,697 Total 789,978 22,171 — 812,149 Notes: (1) Agency mortgage-backed securities presented in this line consist of Japanese and Foreign agency mortgage-backed securities, of which the fair values were ¥504,953 million and ¥61 million, respectively, at March 31, 2020, and ¥ 519,974 51 (2) Other debt securities presented in this line primarily consist of Japanese asset-backed securities (“ABS”), of which the total fair values was million at September 30, 2020. (3) Other debt securities presented in this line primarily consist of Foreign negotiable certificates of deposit (“NCDs”) and ABS, of which the total fair values were ¥271,387 million at March 31, 2020, and ¥319,044 million at September 30, 2020. (4) All Agency mortgage-backed securities presented in this line are Ginnie Mae securities. (5) Amortized cost, net of the allowance for credit losses, of which the amounts related to available-for-sale (6) Accrued interest receivables are excluded from amortized cost, of which the amount was million at September 30, 2020 and included in Acc rued income. The amortized cost, net of allowance for credit losses, and fair value available-for-sale held-to-maturity Amortized cost Due in one year or less Due after one year through five years Due after five years through ten years Due after ten years Total (in millions of yen) Available-for-sale Debt securities: Japanese government bonds 14,588,119 3,630,141 1,550,745 195,548 19,964,553 Japanese local government bonds 30,537 209,317 149,994 17,025 406,873 U.S. Treasury bonds and federal agency securities 625,398 — — — 625,398 Other foreign government bonds 1,024,723 326,539 1,058 1,056 1,353,376 Agency mortgage-backed securities — — — 509,808 509,808 Residential mortgage-backed securities — — — 78,883 78,883 Commercial mortgage-backed securities 6,080 252,315 375,342 800 634,537 Japanese corporate bonds and other debt securities 94,088 820,338 587,344 564,464 2,066,234 Foreign corporate bonds and other debt securities 453,235 343,496 123,123 2,898 922,752 Total 16,822,180 5,582,146 2,787,606 1,370,482 26,562,414 Held-to-maturity Debt securities: Japanese government bonds — 479,947 — — 479,947 Agency mortgage-backed securities — — — 310,031 310,031 Total — 479,947 — 310,031 789,978 Fair value Due in one year or less Due after one year through five years Due after five years through ten years Due after ten years Total (in millions of yen) Available-for-sale Debt securities: Japanese government bonds 14,586,652 3,619,928 1,522,868 190,915 19,920,363 Japanese local government bonds 30,553 209,557 149,982 17,092 407,184 U.S. Treasury bonds and federal agency securities 626,784 — — — 626,784 Other foreign government bonds 1,025,928 328,280 1,058 1,056 1,356,322 Agency mortgage-backed securities — — — 520,025 520,025 Residential mortgage-backed securities — — — 79,980 79,980 Commercial mortgage-backed securities 6,085 254,025 380,219 813 641,142 Japanese corporate bonds and other debt securities 94,089 819,848 585,922 570,169 2,070,028 Foreign corporate bonds and other debt securities 454,356 344,474 123,244 2,898 924,972 Total 16,824,447 5,576,112 2,763,293 1,382,948 26,546,800 Held-to-maturity Debt securities: Japanese government bonds — 491,452 — — 491,452 Agency mortgage-backed securities — — — 320,697 320,697 Total — 491,452 — 320,697 812,149 Credit losses The other-than-temporary impairment losses on available-for-sale securities for the six months ended September 30, 2019 were not significant. No impairment losses were recognized on held-to-maturity securities for the period. As a result of the adoption of the ASU No.2016-13, 2019-04, 2019-05 and 2019-11, no material allowance for credit losses on available-for-sale securities were recognized at April 1, 2020. The MHFG Group recognized billion of allowance for credit losses on available-for-sale securities at September 30, 2020. The increase was due mainly to an increase of credit losses for certain Japanese corporate bonds and other debt securities. allowance for credit losses were recognized on held-to-maturity securities at April 1, 2020 and September 30, 2020, respectively because held-to-maturity securities consist of Japanese government bond and agency mortgage-backed securities like Ginnie Mae securities. See Note 1 “Basis of presentation” for further details of the methodology used to determine the allowance for credit losses. Continuous unrealized loss position The following table shows the gross unrealized losses and fair value of available-for-sale held-to-maturity Less than 12 months 12 months or more Total Fair value Gross unrealized losses Fair value Gross unrealized losses Fair value Gross unrealized losses (in millions of yen) March 31, 2020 Available-for-sale Debt securities: Japanese government bonds 10,339,320 43,204 283,561 7,020 10,622,881 50,224 Japanese local government bonds 162,665 418 34,114 76 196,779 494 U.S. Treasury bonds and federal agency securities — — — — — — Other foreign government bonds 196,990 202 — — 196,990 202 Agency mortgage-backed securities (1) 30,913 227 9,504 207 40,417 434 Residential mortgage-backed securities 9,524 62 5,450 89 14,974 151 Commercial mortgage-backed securities 15,115 85 7,478 21 22,593 106 Japanese corporate bonds and other debt securities 669,572 5,507 608,361 3,265 1,277,933 8,772 Foreign corporate bonds and other debt securities 152,058 165 5,564 3 157,622 168 Total 11,576,157 49,870 954,032 10,681 12,530,189 60,551 Held-to-maturity Debt securities: Agency mortgage-backed securities (2) — — 191,244 1,303 191,244 1,303 Total — — 191,244 1,303 191,244 1,303 September 30, 2020 Available-for-sale Debt securities: Japanese government bonds 9,978,136 23,884 1,234,118 21,390 11,212,254 45,274 Japanese local government bonds 126,991 246 72,086 200 199,077 446 U.S. Treasury bonds and federal agency securities 29,093 2 — — 29,093 2 Other foreign government bonds 278,022 74 — — 278,022 74 Agency mortgage-backed securities (1) 30,948 202 9,799 231 40,747 433 Residential mortgage-backed securities 9,567 41 6,794 82 16,361 123 Commercial mortgage-backed securities 6,052 15 11,396 54 17,448 69 Japanese corporate bonds and other debt securities 565,278 3,028 597,714 5,757 1,162,992 8,785 Foreign corporate bonds and other debt securities 245,311 1,187 2,712 3 248,023 1,190 Total 11,269,398 28,679 1,934,619 27,717 13,204,017 56,396 Held-to-maturity Debt securities: Agency mortgage-backed securities (2) — — — — — — Total — — — — — — Notes: (1) Agency mortgage-backed securities presented in this line consist of Japanese agency mortgage-backed securities, of which the fair values were ¥40,417 million at March 31, 2020, and ¥40,747 million at September 30, 2020. All Japanese agency mortgage-backed securities are issued by Japan Housing Finance Agency, a Japanese government-sponsored enterprise. (2) All Agency mortgage-backed securities presented in this line are Ginnie Mae securities. At September 30, 2020, the MHFG Group did not intend to sell the debt securities in an unrealized loss position and it was not more likely than not that the MHFG Group would be required to sell them before the recovery of their amortized cost bases. For Japanese government bonds and Agency mortgage-backed securities, their entire amortized cost bases were expected to be recovered since the unrealized losses had not resulted from credit deterioration, but primarily from changes in interest rates. For the debt securities other than those described above, except for the securities for which credit losses have been recognized in income, the MHFG Group determined that their entire amortized cost bases were expected to be recovered, after considering various factors such as the extent to which their fair values were below their amortized cost bases, the external and/or internal ratings and the present values of cash flows expected to be collected. Based on the aforementioned evaluation, except for the securities for which credit losses have been recognized in income, the MHFG Group determined that the debt securities in an unrealized loss position were not considered credit losses. Realized gains and losses The following table shows the realized gains and losses on sales of available-for-sale Six months ended September 30, 2019 2020 (in millions of yen) Gross realized gains 36,183 5,101 Gross realized losses (6,167 ) (3,694 ) Net realized gains (losses) on sales of available-for-sale 30,016 1,407 Equity securities Equity securities include securities which have readily determinable fair values, securities which qualify for the practical expedient to estimate fair value using the net asset value per share (or its equivalent), and securities which are without readily determinable fair values. Equity securities which have readily determinable fair values mainly consist of common stock of Japanese listed companies. Equity securities without readily determinable fair values include non-marketable Net gains and losses The following table shows the details of the net gains and losses on Equity securities for the six months ended September 30, 2019 and 2020: Six months ended September 30, 2019 2020 (in millions of yen) Net gains (losses) recognized during the period on equity securities (126,648 ) 266,119 Less: Net gains (losses) recognized during the period on equity securities sold during the period (3,084 ) 34,985 Unrealized gains (losses) recognized during the reporting period on equity securities still held at the (123,564 ) 231,134 Equity securities without readily determinable fair values The following table shows carrying amounts of equity securities without readily determinable fair values, for which the measurement alternative is used, and cumulative amounts due to downward adjustments and impairments and upward adjustments, at March 31, 2020 and September 30, 2020: March 31, 2020 September 30, 2020 (in millions of yen) Carrying amounts at the end of the period 419,775 402,194 Downward adjustments and impairments 2,435 3,800 Upward adjustments 9,128 9,104 The following table shows amounts recognized in earnings during the period due to downward adjustments and impairments and upward adjustments for equity securities without readily determinable fair values. Six months ended September 30, 2019 2020 (in millions of yen) Downward adjustments and impairments 430 1,411 Upward adjustments 6,527 34 The MHFG Group elected to measure all equity securities without readily determinable fair values, which do not qualify for the practical expedient to estimate fair value, using the measurement alternative, which is made on an instrument-by-instrument Other investments The following table summarizes the composition of Other investments at March 31, 2020 and September 30, 2020: March 31, 2020 September 30, 2020 (in millions of yen) Equity method investments 404,513 412,281 Investments held by consolidated investment companies 39,438 55,682 Total 443,951 467,963 Equity method investments Investments in investees over which the MHFG Group has the ability to exert significant influence are accounted for using the equity method of accounting. Such investments included marketable equity securities with carrying values of ¥213,243 million and ¥215,059 million, at March 31, 2020 and September 30, 2020, respectively. The aggregate market values of these marketable equity securities were ¥287,488 million and ¥344,131 million, respectively. The majority of the aggregate market values of these marketable equity securities include Orient Corporation, the Chiba Kogyo Bank, Ltd., Joint Stock Commercial Bank for Foreign Trade of Vietnam and Mizuho Leasing Company, Limited of which the MHFG Group’s proportionate share of the total outstanding common stock were 49.00%, 16.89%, 15.00% and 23.52%, respectively, as of September 30, 2020. In addition, equity method investments include non-marketable equity securities such as Matthews International Capital Management, LLC and Custody Bank of Japan, Ltd. of which the MHFG Group’s proportionate share of the total outstanding common stock were Investments held by consolidated investment companies The MHFG Group consolidates certain investment companies over which it has control through either ownership or other means. Investment companies are subject to specialized industry accounting which requires investments to be carried at fair value, with changes in fair value recorded in earnings. The MHFG Group maintains this specialized industry accounting for investments held by consolidated investment companies, which consist of marketable and non-marketable

Loans

Loans	6 Months Ended
	Sep. 30, 2020
Loans	4. Loans The table below presents loans outstanding by domicile and industry of borrower at March 31, 2020 and September 30, 2020: March 31, 2020 September 30, 2020 (in millions of yen) Domestic: Manufacturing 9,731,028 11,700,375 Construction and real estate 9,603,433 10,172,843 Services 5,992,511 6,294,310 Wholesale and retail 5,219,727 5,415,605 Transportation and communications 3,832,884 3,978,708 Banks and other financial institutions 4,634,442 4,719,863 Government and public institutions 2,198,805 2,639,956 Other industries (Note) 5,389,347 5,517,220 Individuals: Mortgage loans 8,567,099 8,357,042 Other 861,235 798,475 Total domestic 56,030,511 59,594,397 Foreign: Commercial and industrial 20,818,709 20,190,048 Banks and other financial institutions 10,475,277 10,502,326 Government and public institutions 317,284 308,171 Other 35,388 37,572 Total foreign 31,646,658 31,038,117 Total 87,677,169 90,632,514 Less: Unearned income and deferred loan fees—net 149,081 156,767 Total loans before allowance for credit losses on loans 87,528,088 90,475,747 Note: Other industries of domestic includes trade receivables and lease receivables of consolidated VIEs. Loans are generally carried at the principal amount adjusted for unearned income and deferred net nonrefundable loan fees and costs. Loan origination fees, net of certain direct origination costs, are deferred and recognized over the contractual life of the loan as an adjustment of yield using a method that approximates the interest method. Interest income on performing loans is accrued and credited to income as it is earned. Unearned income and discounts or premiums on purchased loans are deferred and recognized over the life of the loan using a method that approximates the interest method. Net losses on sales of loans were ¥179 million and ¥1,178 million, including unrealized losses related to recording loans held for sale at the lower of cost or fair value for the six months ended September 30, 2019 and 2020, respectively. The gains and losses on sales of loans are recorded in Other noninterest income and expenses, respectively. Credit quality information In accordance with the MHFG Group’s credit risk management policies, the Group uses an internal rating system that consists of credit ratings for the corporate portfolio segment and pool allocations for the retail portfolio segment as the basis of its risk management infrastructure. Credit ratings consist of obligor ratings which represent the level of credit risk of the obligor, and transaction ratings which represent the ultimate possibility of losses expected on individual loans by taking into consideration various factors such as collateral or guarantees involved. In principle, obligor ratings are applied to all obligors except those to which pool allocations are applied, and are subject to regular review at least once a year as well as special review which is required whenever the obligor’s credit standing changes. Pool allocations are applied to small loans that are less than a specified amount by pooling customers and loans with similar risk characteristics, and the risk is assessed mainly based on past due status and managed according to such pools. The Group generally reviews the appropriateness and effectiveness of the approach to obligor ratings and pool allocations once a year in accordance with predetermined policies and procedures. See Note 3 “Investments” for the credit losses related to held-to-maturity available-for-sale The Group does not record expected credit losses reversed interest rued income. The table below presents credit quality information of loans MHFG Obligor category (1)(2) Obligor rating Definition Normal A Obligors whose certainty of debt fulfillment is very high, hence their level of credit risk is very low. B Obligors whose certainty of debt fulfillment poses no problems for the foreseeable future, and their level of credit risk is low. C Obligors whose certainty of debt fulfillment and their level of credit risk pose no problems for the foreseeable future. D Obligors whose current certainty of debt fulfillment poses no problems, however, their resistance to future economic environmental changes is low. Watch E1 Obligors that require observation going forward because of either minor concerns regarding their financial position, or their somewhat weak or unstable business conditions. E2 Obligors that require special observation going forward because of problems with their borrowings such as reduced or suspended interest payments, problems with debt fulfillment such as failure to make principal or interest payments, or problems with their financial position as a result of their weak or unstable business conditions. Intensive control F Obligors that are not yet bankrupt but are in financial difficulties and are deemed likely to become bankrupt in the future because of insufficient progress in implementing their management improvement plans or other measures (including obligors that are receiving ongoing support from financial institutions). Substantially bankrupt G Obligors that have not yet become legally or formally bankrupt but are substantially insolvent because they are in serious financial difficulties and are deemed to be incapable of being restructured. Bankrupt H Obligors that have become legally or formally bankrupt. Notes: (1) Special attention obligors are watch obligors with debt in TDR or 90 days or more delinquent debt. Loans to such obligors are considered nonaccrual. (2) The Group classifies loans to special attention, intensive control, substantially bankrupt and bankrupt obligors as nonaccrual loans. September 30, 2020 March 31, 2020 Term loans by origination year Revolving Total Total 2020 2019 2018 2017 2016 Prior to 2016 (in millions of yen) Domestic: Corporate: Large companies: Normal obligors 9,754,935 7,343,964 7,517,546 2,710,108 2,498,507 2,978,989 8,279,869 41,083,918 37,979,353 Watch obligors excluding special attention obligors 424,745 92,446 82,206 56,363 33,737 33,847 196,544 919,888 840,289 Nonaccrual loans 142,730 55,771 41,249 20,295 11,956 29,551 136,213 437,765 343,439 Small and medium-sized Normal obligors 381,487 543,822 456,363 260,146 232,638 485,430 502,124 2,862,010 2,941,599 Watch obligors excluding special attention obligors 46,537 32,174 37,116 13,321 15,523 28,933 30,521 204,125 189,075 Nonaccrual 58,754 15,624 4,294 5,900 2,636 9,849 28,118 125,175 119,759 Retail: Housing Loan: Normal obligors 437,780 668,358 627,669 634,528 783,929 4,879,204 — 8,031,468 8,215,781 Watch obligors excluding special attention obligors 560 1,178 1,827 1,579 2,217 43,397 — 50,758 57,478 Nonaccrual 18,941 6,528 1,525 1,432 1,778 38,456 — 68,660 57,696 Others: Normal obligors 327,506 209,899 152,679 106,359 102,735 361,209 523,640 1,784,027 1,783,779 Watch obligors excluding special attention obligors 36,270 17,587 11,754 6,911 4,534 6,846 12,185 96,087 81,463 Nonaccrual 26,633 6,905 1,945 1,000 965 9,532 11,567 58,547 59,782 Sovereign Normal obligors 1,907,424 264,528 126,868 87,021 92,664 485,721 13,700 2,977,926 2,559,420 Watch obligors excluding special attention obligors 2,859 6,914 2,951 1,134 257 34 — 14,149 10,939 Nonaccrual — — — — — — — — — Banks and other financial institutions Normal obligors 15,637 155,415 261,601 26,841 85,303 74,009 187,102 805,908 790,659 Watch obligors excluding special attention obligors — — — — — — — — — Nonaccrual 167 — 180 — — — 1,600 1,947 — Total domestic 13,582,965 9,421,113 9,327,773 3,932,938 3,869,379 9,465,007 9,923,183 59,522,358 56,030,511 Foreign: Corporate: Normal obligors 10,181,936 5,813,342 3,419,918 1,298,791 804,580 1,624,422 4,630,806 27,773,795 28,555,991 Watch obligors excluding special attention obligors 172,225 43,785 47,998 37,862 15,899 35,532 84,646 437,947 336,470 Nonaccrual 41,085 25,405 12,954 5,422 8,448 21,241 43,592 158,147 135,522 Retail: Normal obligors 3,613 9,806 6,008 2,956 1,517 2,527 102 26,529 30,862 Watch obligors excluding special attention obligors 174 1,110 647 361 109 11 — 2,412 858 Nonaccrual 26 506 287 103 44 1 — 967 6 Sovereign Normal obligors 91,542 99,248 32,403 149,794 5,907 90,988 81,008 550,890 558,384 Watch obligors excluding special attention obligors — — — — — 20,124 — 20,124 19,971 Nonaccrual — 741 — — — — — 741 — Banks and other financial institutions Normal obligors 750,039 654,755 421,876 95,375 4,509 3,536 49,997 1,980,087 2,008,516 Watch obligors excluding special attention obligors 912 152 686 — — — — 1,750 78 Nonaccrual — — — — — — — — — Total foreign 11,241,552 6,648,850 3,942,777 1,590,664 841,013 1,798,382 4,890,151 30,953,389 31,646,658 Total 24,824,517 16,069,963 13,270,550 5,523,602 4,710,392 11,263,389 14,813,334 90,475,747 87,677,169 Notes: (1) Special attention obligors are watch obligors with debt in TDR or 90 days or more delinquent debt. Loans to such obligors are considered nonaccrual. (2) The primary component of the retail portfolio segment is housing loans to individuals which obligor category is classified based on past due status. The trigger to reclassify obligors from normal obligors to watch obligors excluding special attention obligors is when the past due status is more than 30 days. (3) There were no significant revolving line of credit arrangements that converted to term loans during the six months ended September 30, 2020. Nonaccrual loans Loans are considered nonaccrual when, based on current information and events, it is probable that the MHFG Group will be unable to collect all the scheduled payments of principal and interest when due according to the contractual terms of the loans. Factors considered by management in determining if a loan is nonaccrual include delinquency status and the ability of the debtor to make payment of the principal and interest when due. The Group classifies loans to special attention, intensive control, substantially bankrupt and bankrupt obligors as nonaccrual loans. Nonaccrual loans include loans past due for 90 days or more and restructured loans that meet the definition of a TDR in accordance with ASC 310. There are no loans that are ninety days past due and still accruing. The Group does not have any loans to borrowers that cause management to have serious doubts as to the ability of such borrowers to comply with the present loan repayment terms for the periods presented other than those already designated as nonaccrual loans. The majority of nonaccrual loans have no contractual delinquency due to interest reductions and/or postponement of principal and interest. In March 2020, the Coronavirus, Aid, Relief, and Economic Security Act (“the CARES Act”) was approved. The CARES Act and U.S. banking agencies have among other items, provided optional, temporary relief related to accounting for certain TDRs. The temporary TDR relief is available to banks for loan modifications related to obligors who were adversely impacted by COVID-19. With regard to nonaccrual loans, interest accruals and the amortization of net origination fees are suspended and capitalized interest is written off. Cash received on nonaccrual loans is accounted for as a reduction of the loan principal if the ultimate collectibility of the principal amount is in doubt, otherwise, as interest income. Loans are not restored to accrual status until interest and principal payments are current and future payments are reasonably assured. Nonaccrual loans are restored to accrual status, when the MHFG Group determines that the borrower poses no concerns regarding current certainty of debt fulfillment. In general, such determination is made if the borrower qualifies for an obligor rating of E2 or above and is not classified as a special attention obligor. With respect to loans restructured in a TDR, in general, such loans are restored to accrual status, when the borrower qualifies for an obligor rating of D or above. The table below presents nonaccrual loans information at March 31, 2020 and September 30, 2020: Amortized cost Nonaccrual loans with an allowance Nonaccrual loans without an allowance Total nonaccrual loans Interest income recognized (in millions of yen) March 31, 2020 Domestic: Corporate: Large companies 333,442 9,997 343,439 4,155 Small and medium-sized 102,786 16,973 119,759 1,724 Retail: Housing Loan 28,263 29,433 57,696 937 Others 36,220 23,562 59,782 846 Total domestic 500,711 79,965 580,676 7,662 Foreign: Total foreign 95,289 40,239 135,528 3,032 Total 596,000 120,204 716,204 10,694 September 30, 2020 Domestic: Corporate: Large companies 416,637 21,128 437,765 2,501 Small and medium-sized 105,556 19,619 125,175 777 Retail: Housing Loan 40,358 28,302 68,660 535 Others 36,270 22,277 58,547 373 Banks and other financial institutions 1,947 — 1,947 3 Total domestic 600,768 91,326 692,094 4,189 Foreign: Total foreign 110,295 49,560 159,855 958 Total 711,063 140,886 851,949 5,147 Notes: (1) Amounts represent the outstanding bal a (2) Amounts represent the amount of interest income on nonaccrual loans recognized on a cash basis and included in Interest income on loans in the consolidated statements of income. (3) The majority of total foreign consist of corporate. The remaining balance of nonaccrual loans that have been partially charged off, was ¥20,378 million and ¥32,783 million as of March 31, 2020 and September 30, 2020 respectively. Troubled debt restructurings The MHFG Group considers a loan modification to be a TDR when, for economic or legal reasons related to the obligor’s financial difficulties, it grants a concession to the obligor that it would not otherwise consider. The Group considers the relevant obligor to be in financial difficulty generally when its obligor rating is E2 or below.The following table presents modified loans that were determined to be TDRs during the six months ended September 30, 2019 and 2020: Loan forgiveness or debt to equity swaps Interest rate reduction and/or postponement of principal and/or Recorded investment (1) Charge-offs (in millions of yen) September 30, 2019 Domestic: Corporate: Large companies 689 3,806 152,373 Small and medium-sized — — 55,344 Retail: Housing Loan — — 3,742 Others — — 7,468 Total domestic 689 3,806 218,927 Foreign: Total foreign 470 4,922 38,646 Total 1,159 8,728 257,573 September 30, 2020 Domestic: Corporate: Large companies — — 264,952 Small and medium-sized — — 54,760 Retail: Housing Loan — — 14,690 Others — — 9,130 Banks and other financial institutions — — 1,600 Total domestic — — 345,132 Foreign: Total foreign — — 80,889 Total — — 426,021 Notes: (1) Amounts represent the b o (2) The majority of total foreign consist of corporate Payment default is deemed to occur when the loan becomes three months past due or the obligor is downgraded to the category of substantially bankrupt or bankrupt. The following table presents payment defaults which occurred during the six months ended September 30, 2019 and 2020 with respect to the loans modified as TDRs within the previous twelve months: Recorded investment September 30, 2019 September 30, 2020 (in millions of yen) Domestic: Corporate: Large companies 5,875 2,084 Small and medium-sized 2,444 3,861 Retail: Housing Loan 686 505 Others 1,349 1,104 Total domestic 10,354 7,554 Foreign: Total foreign 6,436 43,786 Total 16,790 51,340 Age analysis of past due loans The table below presents an analysis of the age of the amortized cost basis in loans that are past due at March 31, 2020 and September 30, 2020: 30-59 days past due 60-89 days past due 90 days or more past due Total past due Current Total (in millions of yen) March 31, 2020 Domestic: Corporate: Large companies 2,146 2,013 38,364 42,523 39,120,558 39,163,081 Small and medium-sized 2,347 894 9,187 12,428 3,238,005 3,250,433 Retail: Housing Loan 15,703 10,078 26,690 52,471 8,278,484 8,330,955 Others 6,179 2,013 15,239 23,431 1,901,593 1,925,024 Sovereign — — — — 2,570,359 2,570,359 Banks and other financial institutions — — — — 790,659 790,659 Total domestic 26,375 14,998 89,480 130,853 55,899,658 56,030,511 Foreign: Total foreign 1,214 181 28,722 30,117 31,616,541 31,646,658 Total 27,589 15,179 118,202 160,970 87,516,199 87,677,169 September 30, 2020 Domestic: Corporate: Large companies 311 269 38,868 39,448 42,402,123 42,441,571 Small and medium-sized 2,093 604 11,226 13,923 3,177,387 3,191,310 Retail: Housing Loan 15,831 7,870 25,922 49,623 8,101,263 8,150,886 Others 4,720 1,436 14,152 20,308 1,918,353 1,938,661 Sovereign — — — — 2,992,075 2,992,075 Banks and other financial institutions — — — — 807,855 807,855 Total domestic 22,955 10,179 90,168 123,302 59,399,056 59,522,358 Foreign: Total foreign 1,826 636 60,535 62,997 30,890,392 30,953,389 Total 24,781 10,815 150,703 186,299 90,289,448 90,475,747 Note: The majority of total foreign consist of corporate . Loans held for sale Loans that have been identified for sale are classified as loans held for sale within Other assets and are accounted for at the lower of cost or fair value. The outstanding balance of loans held for sale was ¥60,084 million and ¥22,404 million at March 31, 2020 and September 30, 2020, respectively.

Allowance for credit losses on

Allowance for credit losses on loans	6 Months Ended
	Sep. 30, 2020
Allowance for credit losses on loans	5. Allowance for credit losses on loans The MHFG Group divides its overall portfolio into domestic and foreign portfolios, and categorizes the domestic portfolio into four portfolio segments according to their risk profiles: corporate, retail, sovereign, and banks and financial institutions. When management estimates current expected credit losses to determine the allowance for credit losses, small balance, homogeneous loans are classified in the retail portfolio segment, and loans other than these are classified in the corporate portfolio segment. The corporate portfolio segment consists of loans originated primarily by MHBK and MHTB, and includes mainly business loans such as those used for working capital and capital expenditure, as well as loans for which the primary source of repayment of the obligation is income generated by the relevant assets such as project finance, asset finance and real estate finance. The corporate portfolio segment also includes loans of subsidiaries other than MHBK and MHTB, such as consolidated VIEs and overseas subsidiaries. The corporate portfolio segment is divided into two classes based on their risk characteristics: large companies, and small and medium-sized on loans and Note 4 “Loans” for further details of obligor ratings and pool allocations. Changes in Allowance for credit losses on loans by portfolio segment for the six months ended September 30, 2019 and 2020 are shown below: Corporate Retail Total (in millions of yen) Six months ended September 30, 2019 Balance at beginning of period 277,955 29,246 307,201 Provision (credit) for credit losses on loans 12,268 1,505 13,773 Charge-offs (25,147 ) (3,887 ) (29,034 ) Recoveries 2,785 1,269 4,054 Net charge-offs (22,362 ) (2,618 ) (24,980 ) Others (Note) (4,570 ) (2 ) (4,572 ) Balance at end of period 263,291 28,131 291,422 Six months ended September 30, 2020 Balance at beginning of period 413,026 27,829 440,855 April 1, 2020 adoption of CECL 77,514 78,241 155,755 Adjusted Balance at beginning of period 490,540 106,070 596,610 Provision (credit) for credit losses on loans 64,133 (11,051 ) 53,082 Charge-offs (28,417 ) (3,446 ) (31,863 ) Recoveries 5,260 479 5,739 Net charge-offs (23,157 ) (2,967 ) (26,124 ) Others (Note) (997 ) (45 ) (1,042 ) Balance at end of period 530,519 92,007 622,526 Note: Others includes primarily foreign exchange translation.

Other assets and liabilities

Other assets and liabilities	6 Months Ended
	Sep. 30, 2020
Other assets and liabilities	6. Other assets and liabilities The following table sets forth the details of other assets and liabilities at March 31, 2020 and September 30, 2020: March 31, 2020 September 30, 2020 (in millions of yen) Other assets: Accounts receivable: Receivables from brokers, dealers and customers for securities transactions 783,439 898,924 Other 358,702 416,064 Collateral pledged: Collateral pledged for derivative transactions 1,246,026 1,079,050 Margins provided for futures contracts 602,039 316,791 Other 941,167 909,155 Prepaid pension cost 711,981 986,767 Right-of-use 613,068 586,365 Security deposits 107,294 108,204 Loans held for sale 60,084 22,404 Other 542,079 540,514 Total 5,965,879 5,864,238 Other liabilities: Accounts payable: Payables to brokers, dealers and customers for securities transactions 2,161,075 2,065,408 Other 375,127 365,446 Guaranteed trust principal ( Note 824,431 808,172 Lease liabilities 627,250 600,087 Collateral accepted: Collateral accepted for derivative transactions 846,426 587,426 Margins accepted for futures contracts 797,317 558,138 Unearned income 122,072 120,352 Other 1,244,697 1,194,591 Total 6,998,395 6,299,620 Note: Guaranteed trust principal, included in All other liabilities in the disclosure about consolidated VIEs in the accompanying balance sheets, is a liability of certain consolidated trust arrangements that meet the definition of a VIE for which the MHFG Group provides guarantees for the repayment of principal. See Note 15 “Variable interest entities and securitizations” for further discussion of the guaranteed principal money trusts.

Preferred and common stock

Preferred and common stock	6 Months Ended
	Sep. 30, 2020
Preferred and common stock	7. Preferred and common stock Preferred stock The composition of preferred stock at March 31, 2020 and September 30, 2020 is as follows: Class of stock March 31, 2020 September 30, 2020 Authorized Issued Authorized Issued (number of shares) Class XIV preferred stock 90,000,000 — 90,000,000 — Class XV preferred stock 90,000,000 — 90,000,000 — Class XVI preferred stock 150,000,000 — 150,000,000 — Common stock The number of issued shares of common stock at March 31, 2020 and September 30, 2020 was 2,539,249,894. There was no increase or decrease during the six months ended September 30, 2020.

Accumulated other comprehensive

Accumulated other comprehensive income (loss), net of tax	6 Months Ended
	Sep. 30, 2020
Accumulated other comprehensive income (loss), net of tax	8. Accumulated other comprehensive income (loss), net of tax Changes in each component of Accumulated other comprehensive income (loss), net of tax (“AOCI”) for the six months ended September 30, 2019 and 2020 are as follows: Six months ended September 30, 2019 2020 (in millions of yen) AOCI, balance at beginning of period, previously reported 164,021 (9,494 ) Cumulative effect of change in accounting principles (Note) (1,052 ) — AOCI, balance at beginning of period, adjusted 162,969 (9,494 ) Net unrealized gains (losses) on available-for-sale Balance at beginning of period 22,019 (19,592 ) Unrealized holding gains (losses) during period 25,843 644 Less: reclassification adjustments for losses (gains) included in net income (20,824 ) 754 Change during period 5,019 1,398 Balance at end of period 27,038 (18,194 ) Foreign currency translation adjustments: Balance at beginning of period, previously reported (58,558 ) (109,872 ) Cumulative effect of change in accounting principles (Note) (1,052 ) — Balance at beginning of period, adjusted (59,610 ) (109,872 ) Foreign currency translation adjustments during period (63,466 ) (36,652 ) Less: reclassification adjustments for losses (gains) included in net income — (409 ) Change during period (63,466 ) (37,061 ) Balance at end of period (123,076 ) (146,933 ) Pension liability adjustments: Balance at beginning of period 196,446 69,455 Unrealized gains (losses) during period (1,720 ) 190,394 Less: reclassification adjustments for losses (gains) included in net income (2,130 ) 672 Change during period (3,850 ) 191,066 Balance at end of period 192,596 260,521 Own credit risk adjustments: Balance at beginning of period 4,114 50,515 Unrealized gains (losses) during period 7,320 (9,340 ) Less: reclassification adjustments for losses (gains) included in net income (1,277 ) (2,732 ) Change during period 6,043 (12,072 ) Balance at end of period 10,157 38,443 Total other comprehensive income (loss), net of tax attributable to MHFG shareholders (56,254 ) 143,331 AOCI, balance at end of period 106,715 133,837 Note: The MHFG Group adopted ASU No.2017-12, No.2017-12”) No.2017-12 The following table shows the amounts reclassified out of AOCI into net income during the six months ended September 30, 2020: Six months ended September 30, 2020 Before tax (1) Tax effect (2) Net of tax before allocation to noncontrolling interests Net of tax attributable to noncontrolling interests (2) Net of tax attributable to MHFG shareholders (in millions of yen) Amounts reclassified out of AOCI into net income: Affected line items in the Net unrealized gains (losses) on available-for-sale (1,065 ) 306 (759 ) 5 (754 ) Investment gains (losses)-net Provision (credit) for credit Foreign currency translation adjustments 409 — 409 — 409 Foreign exchange gains (losses)-net Pension liability adjustments (1,004 ) 321 (683 ) 11 (672 ) Salaries and employee benefits Own credit risk adjustments 4,111 (1,259 ) 2,852 (120 ) 2,732 Other noninterest income (expenses) Total 2,451 (632 ) 1,819 (104 ) 1,715 Notes: (1) The financial statement li n e (2) 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.

Regulatory matters

Regulatory matters	6 Months Ended
	Sep. 30, 2020
Regulatory matters	9. Regulatory matters Regulatory capital requirements MHFG, MHBK, and MHTB are subject to regulatory capital requirements administered by the Financial Services Agency in accordance with the provisions of Japan’s Banking Act and related regulations. Certain foreign banking subsidiaries are subject to regulation and control by local supervisory authorities, including central banks. Capital adequacy ratios and leverage ratios of MHFG, MHBK, and MHTB as of March 31, 2020 and September 30, 2020 calculated in accordance with Japanese GAAP and the guidelines established by the Financial Services Agency are set forth in the following table: March 31, 2020 September 30, 2020 Amount Ratio Amount Ratio (in billions of yen, except percentages) Consolidated: MHFG: Common Equity Tier 1 capital: Required (1) 4,978 8.01 5,159 8.01 Actual 7,245 11.65 7,453 11.57 Tier 1 capital: Required (1) 5,910 9.51 6,125 9.51 Actual 9,024 14.52 9,468 14.69 Total risk-based capital: Required (1) 7,152 11.51 7,413 11.51 Actual 10,722 17.25 11,133 17.28 Leverage Ratio: Required 6,629 3.00 5,874 (2) 3.00 Actual 9,024 4.08 9,468 (2) 4.83 MHBK: Common Equity Tier 1 capital: Required 2,567 4.50 2,689 4.50 Actual 6,501 11.39 6,756 11.30 Tier 1 capital: Required 3,422 6.00 3,585 6.00 Actual 8,275 14.50 8,765 14.66 Total risk-based capital: Required 4,563 8.00 4,780 8.00 Actual 9,865 17.29 10,338 17.30 Leverage Ratio: Required 6,160 3.00 5,450 (2) 3.00 Actual 8,275 4.02 8,765 (2) 4.82 MHTB: Common Equity Tier 1 capital: Required 93 4.50 87 4.50 Actual 489 23.64 509 26.24 Tier 1 capital: Required 124 6.00 116 6.00 Actual 489 23.66 509 26.24 Total risk-based capital: Required 165 8.00 155 8.00 Actual 491 23.74 510 26.27 Leverage Ratio: Required 216 3.00 156 (2) 3.00 Actual 489 6.79 509 (2) 9.79 March 31, 2020 September 30, 2020 Amount Ratio Amount Ratio (in billions of yen, except percentages) Non-consolidated: MHBK: Common Equity Tier 1 capital: Required 2,403 4.50 2,525 4.50 Actual 6,130 11.47 6,369 11.34 Tier 1 capital: Required 3,204 6.00 3,367 6.00 Actual 7,905 14.80 8,381 14.93 Total risk-based capital: Required 4,272 8.00 4,489 8.00 Actual 9,482 17.75 9,943 17.71 Leverage Ratio: Required 5,884 3.00 5,178 (2) 3.00 Actual 7,905 4.03 8,381 (2) 4.85 MHTB: Common Equity Tier 1 capital: Required 93 4.50 87 4.50 Actual 475 23.10 494 25.49 Tier 1 capital: Required 123 6.00 116 6.00 Actual 475 23.10 494 25.49 Total risk-based capital: Required 165 8.00 155 8.00 Actual 477 23.18 494 25.52 Leverage Ratio: Required 214 3.00 153 (2) 3.00 Actual 475 6.66 494 (2) 9.66 Notes: (1) The required ratios disclosed above, at March 31, 2020 and September 30, 2020, include the capital conservation buffer of 2.5%, the countercyclical capital buffer of 0.01%, and the additional loss absorbency requirements for global systemically important banks (“G-SIBs”) (“D-SIBs”) (2) The required and actual amounts disclosed above at September 30, 2020 exclude amounts of deposits to the Bank of Japan. MHFG’s securities subsidiary in Japan is also subject to the capital adequacy requirement under Japan’s Financial Instruments and Exchange Act. Failure to maintain a minimum capital ratio will trigger mandatory regulatory actions. Management believes, as of each latest balance sheet date, that MHFG, MHBK, MHTB, and their securities subsidiary in Japan and foreign banking subsidiaries were in compliance with all capital adequacy requirements to which they were subject.

Earnings per common share

Earnings per common share	6 Months Ended
	Sep. 30, 2020
Earnings per common share	10. Earnings per common share Basic earnings per common share are computed by dividing net income attributable to MHFG common shareholders by the weighted average number of common shares outstanding during the period. Diluted earnings per common share reflect all dilutive potential common shares such as stock options. The following table sets forth the computation of basic and diluted earnings per common share for the six months ended September 30, 2019 and 2020: Six months ended September 30, 2019 2020 (in millions of yen) Net income: Net income attributable to MHFG common shareholders 212,984 315,886 Effect of dilutive securities — — Net income attributable to common shareholders after assumed conversions 212,984 315,886 Six months ended September 30, 2019 2020 (thousands of shares) Shares: Weighted average common shares outstanding 2,536,800 2,537,272 Effect of dilutive securities: Stock options and the common shares of MHFG under the stock compensation programs (Note) 209 93 Weighted average common shares after assumed conversions 2,537,009 2,537,365 Six months ended September 30, 2019 2020 (in yen) Earnings per common share: Basic net income per common share 83.96 124.50 Diluted net income per common share (Note) 83.95 124.49 Note: For the six months ended September 30, 2020, 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.

Income taxes

Income taxes	6 Months Ended
	Sep. 30, 2020
Income taxes	11. Income taxes The following table presents the components of Income tax expense for the six months ended September 30, 2019 and 2020: Six months ended 2019 2020 (in millions of yen) Current tax expense 88,437 79,954 Deferred tax expense (benefit) (5,317 ) 57,807 Total income tax expense 83,120 137,761 The preceding table does not reflect the tax effects of items recorded directly in Equity for the six months ended September 30, 2019 and 2020. The detailed amounts recorded directly in Equity are as follows: Six months ended 2019 2020 (in millions of yen) Net unrealized gains (losses) on available-for-sale Unrealized gains (losses) 11,023 579 Less: reclassification adjustments (9,192 ) 306 Total 1,831 885 Pension liability adjustments: Unrealized gains (losses) (643 ) 83,994 Less: reclassification adjustments (937 ) 321 Total (1,580 ) 84,315 Own credit risk adjustments: Unrealized gains (losses) (43 ) (2,351 ) Less: reclassification adjustments (588 ) (1,259 ) Total (631 ) (3,610 ) Total tax effect before allocation to noncontrolling interests (380 ) 81,590 The statutory tax rates were both 30.62% as of September 30, 2019 and 2020. The effective tax rates, 26.77% and 25.15% for the six months ended September 30, 2019 and 2020, respectively, differed from the statutory tax rates. The difference of the tax rates for the six months ended September 30, 2019 was immaterial. The difference of the tax rates for the six months ended September 30, 2020 resulted mainly from the effect of noncontrolling interest income At September 30, 2020, the MHFG Group had net operating loss carryforwards totaling ¥623 billion. The total amount of unrecognized tax benefits was ¥4,382 million at September 30, 2020, which would, if recognized, affect the Group’s effective tax rate. The Group classifies interest and penalties accrued relating to unrecognized tax benefits as Income tax expense. A portion of unrecognized tax benefits at March 31, 2020 was resolved in the six months period ended September 30, 2020 , for also

Pension and other employee bene

Pension and other employee benefit plans	6 Months Ended
	Sep. 30, 2020
Pension and other employee benefit plans	12. Pension and other employee benefit plans The following table summarizes the components of net periodic benefit cost of the severance indemnities and pension plans of the MHFG Group for the six months ended September 30, 2019 and 2020: Six months ended 2019 2020 (in millions of yen) Service cost-benefits earned during the period 22,729 22,695 Interest costs on projected benefit obligations 2,666 2,931 Expected return on plan assets (20,158 ) (20,073 ) Amortization of prior service cost (benefits) 19 205 Amortization of net actuarial loss (gain) (3,064 ) 836 Special termination benefits 2,188 4,981 Net periodic benefit cost 4,380 11,575 In September 2020, based on various approvals, MHFG and certain domestic subsidiaries communicated to their employees an 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. Accordingly, the MHFG Group recognized ¥73,998 million of prior service benefits for the six months ended September 30, 2020. The total contribution of approximately ¥41 billion is expected to be paid to the pension plans during the fiscal year ending March 31, 2021. The amount has been changed from which previously disclosed in the consolidated financial statements for the fiscal year ended March 31, 2020, in order to reflect the amendment to the pension plans which is effective as of October 1, 2020. For the six months ended September 30, 2020, the total contribution of ¥25 billion has been paid to the pension plans. The additional contribution of ¥16 billion is expected to be paid during the remainder of the fiscal year ending March 31, 2021.

Derivative financial instrument

Derivative financial instruments	6 Months Ended
	Sep. 30, 2020
Derivative financial instruments	13. Derivative financial instruments The MHFG Group enters into derivative financial instruments in response to the diverse needs of customers, to manage the risk related to the assets and liabilities of the Group, as part of its asset and liability management, and for proprietary trading purposes. The Group is exposed primarily to market risk associated with interest rate, commodity, foreign currency, and equity products. Market risk arises from changes in market prices or indices, interest rates and foreign exchange rates that may result in an adverse change in the market value of the financial instrument or an increase in its funding costs. Exposure to market risk is managed by imposing position limits and monitoring procedures and by initiating hedging transactions. In addition to market risk, the Group is exposed to credit risk associated with counterparty default or nonperformance in respect of transactions. Counterparty credit risk arises when a counterparty fails to perform according to the terms and conditions of the contract and the value of the underlying collateral held, if applicable, is not sufficient to recover resulting losses. The exposure to counterparty credit risk is measured by the fair value of all derivatives and its potential exposure at the balance sheet dates. The exposure to counterparty credit risk is managed by entering into legally enforceable master netting agreements to mitigate the overall counterparty credit risk, requiring underlying collateral and guarantees based on an individual credit analysis of each obligor and evaluating the credit features of each instrument. In addition, credit approvals, limits and monitoring procedures are also imposed. Notional and fair value amounts of derivative instruments The following table summarizes the notional and fair value amounts of derivative instruments outstanding as of March 31, 2020 and September 30, 2020. The fair values of derivatives are presented on a gross basis, derivative receivables and payables are not offset. In addition, they are not offset against the amounts recognized for the right to reclaim cash collateral or the obligation to return cash collateral under master netting agreements in the consolidated balance sheets, or the table below. Fair value Derivative receivables (2) Derivative payables (2) March 31, 2020 Notional amount (1) Designated as hedges Not designated as hedges Designated as hedges Not designated as hedges (in billions of yen) Interest rate contracts 1,123,546 — 7,232 — 6,788 Foreign exchange contracts 185,359 — 2,926 — 2,899 Equity-related contracts 6,684 — 310 — 266 Credit-related contracts 4,676 — 30 — 29 Other contracts 400 — 38 — 39 Total 1,320,665 — 10,536 — 10,021 Fair value Derivative receivables (2) Derivative payables (2) September 30, 2020 Notional amount (1) Designated as hedges Not designated as hedges Designated as hedges Not designated as hedges (in billions of yen) Interest rate contracts 1,084,971 — 6,135 — 5,728 Foreign exchange contracts 174,856 — 2,143 — 2,160 Equity-related contracts 7,012 — 397 — 260 Credit-related contracts 7,742 — 55 — 77 Other contracts 397 — 28 — 26 Total 1,274,978 — 8,758 — 8,251 Notes: (1) Notional amount includes the sum of gross long and gross short third-party contracts. (2) Derivative receivables and payables are recorded in Trading account assets and Trading account liabilities, respectively. The MHFG Group provided and/or accepted cash collateral for derivative transactions under master netting agreements. The cash collateral, which was not offset against derivative positions, was included in Other assets and Other liabilities, respectively, of which the amounts were ¥1,246 billion and ¥846 billion at March 31, 2020, and ¥1,079 billion and ¥587 billion at September 30, 2020, respectively. Hedging activities In order to qualify for hedge accounting, a derivative must be considered highly effective at reducing the risk associated with the exposure being hedged. Each derivative must be designated as a hedge, with documentation of the risk management objective and strategy, including identification of the hedging instrument, the hedged item and the risk exposure, and how effectiveness is to be assessed prospectively and retrospectively. The extent to which a hedging instrument is effective at achieving offsetting changes in fair value or cash flows must be assessed at least quarterly. The MHFG Group’s hedging activities include fair value and net investment hedges. Net investment hedges The MHFG Group uses forward foreign exchange contracts and foreign currency-denominated debt instruments to protect the value of net investments in non-Japanese The following table summarizes gains and losses information related to net investment hedges for the six months ended September 30, 2019 and 2020: Gains (losses) recorded in other for six months ended September 30, 2019 2020 (in millions of yen) Financial instruments hedging foreign exchange risk (1,044 ) 1,538 Total (1,044 ) 1,538 Note: Related to the net investment hedges, gains (losses) of ¥(260) million and ¥(1,312) million were reclassified Derivative instruments not designated The MHFG Group enters into the following derivative transactions that do not qualify for hedge accounting with a view to implementing risk management strategies: (1) interest-rate swap transactions for the purpose of economically managing the interest-rate risks in deposits, loans etc., (2) currency swap transactions for the purpose of economically managing the foreign exchange risk of these assets, and (3) credit derivatives for the purpose of economically managing the credit risk in loans, residential mortgage-backed securities (“RMBS”), commercial mortgage-backed securities (“CMBS”), collateralized loan obligations (“CLO”) and other similar assets. Such derivatives are accounted for as trading positions. The changes in fair value of these instruments are primarily recorded in Trading account gains (losses)—net, even though they are used to mitigate or transform the risk of exposures arising from banking activities. The net gains (losses) resulting from changes in the fair value of certain credit derivatives where the Group purchases protection to mitigate its credit risk exposure, related to its corporate loan portfolio, is recorded in Other noninterest income (expenses). The following table summarizes gains and losses on derivatives not designated or qualifying as hedges during the six months ended September 30, 2019 and 2020: Gains (losses) recorded in income for six months ended September 30, 2019 2020 (in millions of yen) Interest rate contracts 210,909 32,791 Foreign exchange contracts (30,736 ) 26,277 Equity-related contracts (1) (494 ) (31,999 ) Credit-related contracts (2) (3,546 ) (29,219 ) Other contracts (1,650 ) 26,692 Total 174,483 24,542 Notes: (1) The net gains (losses) excluded from the assessment of the effectiveness of fair value hedges is not included (2) Amounts include the net gains (losses) of ¥(426) million and ¥(1,221) million on the credit derivatives economically managing the credit risk of loans during the six months ended September 30, 2019 and 2020, respectively. Credit derivatives A credit derivative is a bilateral contract between a seller and a buyer of protection against the credit risk of a particular entity. Credit derivatives generally require that the seller of credit protection make payments to the buyer upon the occurrence of predefined credit events, which include bankruptcy, dissolution or insolvency of the referenced entity. The MHFG Group either purchases or writes protection on either a single name or a portfolio of reference credits. The Group enters into credit derivatives to help mitigate credit risk in its corporate loan portfolio and other cash positions, to take proprietary trading positions, and to facilitate client transactions. The notional amount of credit derivatives represents the maximum potential amount of future payments the seller could be required to make. If the predefined credit event occurs, the seller will generally have a right to collect on the underlying reference credit and the related cash flows, while being liable for the full notional amount of credit protection to the buyer. The Group manages credit risk associated with written protection by purchasing protection with identical or similar underlying reference credits, which substantially offsets its exposure. Thus, the notional amount is not necessarily a reliable indicator of the Group’s actual loss exposure. The following table summarizes the notional and fair value amounts of credit derivatives at March 31, 2020 and September 30, 2020: March 31, 2020 September 30, 2020 Notional amount Fair value Notional amount Fair value (in billions of yen) Credit protection written: Investment grade 1,400 (5 ) 2,687 37 Non-investment 416 — 530 8 Total 1,816 (5 ) 3,217 45 Credit protection purchased 3,028 6 4,693 (67 ) Note: The rating scale is based upon either the external ratings or the internal ratings of the underlying reference credit. The lowest investment grade rating is considered to be BBB - non-investment Non-investment The following table shows the maximum potential amount of future payments for credit protection written by expiration period at March 31, 2020 and September 30, 2020: Maximum payout/Notional amount March 31, 2020 September 30, 2020 (in billions of yen) One year or less 270 233 After one year through five years 1,368 2,793 After five years 178 191 Total 1,816 3,217 Note: The maximum potential amount of future payments is the aggregate notional amount of the credit derivatives where the Group wrote the credit protection, and it has not been reduced by the effect of any amounts that the Group may possibly collect on the underlying assets and the related cash flows, nor netted against that of credit protection purchased. Credit-related contingent features Certain of the MHFG Group’s derivative instruments contain provisions that require the Group’s debt to maintain an investment grade credit rating from the major credit rating agencies. If the Group’s debt credit rating were to fall below investment grade, the counterparties to the derivative instruments could request immediate payment or demand immediate and ongoing full overnight collateralization on derivative instruments which are in net liability positions for the Group. The following table shows the quantitative information about derivative instruments with credit-risk-related contingent features at March 31, 2020 and September 30, 2020: March 31, September 30, (in billions of yen) Aggregate fair value of derivative instruments with credit-risk-related contingent features in net liability positions 888 747 Collateral provided to counterparties in the normal course of business 818 703 Amount required to be posted as collateral or settled immediately if credit-risk-related contingent features were triggered 70 44

Commitments and contingencies

Commitments and contingencies	6 Months Ended
	Sep. 30, 2020
Commitments and contingencies	14. Commitments and contingencies Obligations under guarantees The MHFG Group provides guarantees or indemnifications to counterparties to enhance their credit standing and enable them to complete a variety of business transactions. A guarantee represents an obligation to make payments to third parties if the counterparty fails to fulfill its obligation under a borrowing arrangement or other contractual obligation. The Group records all guarantees and similar obligations subject to ASC 460, “Guarantees” (“ASC 460”) at fair value in the consolidated balance sheets at the inception of the guarantee. The table below summarizes the maximum potential amount of future payments by type of guarantee at March 31, 2020 and September 30, 2020. The maximum potential amount of future payments disclosed below represents the contractual amounts that could be required to be repaid in the event of the guarantees being executed, without consideration of possible recoveries under recourse provisions or from collateral held. With respect to written options included in derivative financial instruments in the table below, in theory, the MHFG Group is exposed to unlimited losses; therefore, the table shows the notional amounts of the contracts as a substitute for the maximum exposure. March 31, 2020 September 30, 2020 (in billions of yen) Performance guarantees 2,456 2,527 Guarantees on loans 301 266 Guarantees on securities 110 96 Other guarantees 2,314 2,306 Guarantees for the repayment of trust principal 59 31 Liabilities of trust accounts 446 456 Derivative financial instruments 21,756 21,097 The table below presents the maximum potential amount of future payments of performance guarantees, guarantees on loans, guarantees on securities and other guarantees classified based on internal ratings at March 31, 2020 and September 30, 2020: March 31, 2020 September 30, 2020 (in billions of yen) Investment grade 4,233 4,079 Non-investment 948 1,116 Total 5,181 5,195 Note: Investment grade in the internal rating scale generally corresponds to BBB- Other off-balance-sheet In addition to guarantees, the MHFG Group issues other off-balance-sheet The table below summarizes the contractual amounts with regard to these undrawn commitments at March 31, 2020 and September 30, 2020: March 31, 2020 September 30, 2020 (in billions of yen) Commitments to extend credit (Note) 76,633 86,359 Commercial letters of credit 690 537 Total 77,323 86,896 Note: Commitments to extend credit include commitments to invest in securities. Legal proceedings and investigations The MHFG Group is involved in normal collection proceedings initiated by the Group, other legal proceedings and investigations in the ordinary course of business. In accordance with ASC 450, the Group recognizes a liability for loss contingencies arising from such proceedings and investigations when a loss is probable and the loss amount or the range of the loss can be reasonably estimated. If a loss does not meet this condition but is reasonably possible, the Group does not recognize a liability but discloses the detail of such proceedings and investigations. Based on the information available as of the date of the consolidated financial statements, the Group believes that the outcome of the collection, legal proceedings and investigations will not have a significant adverse effect on the consolidated financial statements.

Variable interest entities and

Variable interest entities and securitizations	6 Months Ended
	Sep. 30, 2020
Text Block [Abstract]
Variable interest entities and securitizations	15. Variable interest entities and securitizations Variable interest entities In the normal course of business, the MHFG Group is involved with VIEs primarily through the following types of transactions: asset-backed commercial paper/loan programs, asset-backed securitizations, investments in securitization products, investment funds, trust arrangements, structured finance, and funding vehicles. The Group consolidates certain of these VIEs, where the Group is deemed to be the primary beneficiary because it has both (1) the power to direct the activities of the VIE that most significantly impact the VIE’s economic performance and (2) the obligation to absorb losses or the right to receive benefits that could potentially be significant to the VIE. The MHFG Group reassesses whether it is the primary beneficiary on an ongoing basis as long as the Group has any continuing involvement with the VIE. There are also other VIEs, where the Group has determined that it is not the primary beneficiary but has significant variable interests. In evaluating the significance of the variable interests, the Group takes into consideration the extent of its involvement with each VIE, such as the seniority of its investments, the share of its holding in each tranche and the variability it expects to absorb, as well as other relevant facts and circumstances. The likelihood of loss is not necessarily relevant to the determination of significance, and therefore, “significant” does not imply that there is high likelihood of loss. The maximum exposure to loss that is discussed in this section refers to the maximum loss that the Group could possibly be required to record in its consolidated statements of income as a result of its involvement with the VIEs. This represents exposures associated with both on-balance-sheet off-balance-sheet The table below shows the consolidated assets of the Group’s consolidated VIEs as well as total assets and maximum exposure to loss for its significant unconsolidated VIEs, in which the Group has determined that its maximum exposure to loss is greater than specific thresholds or meets certain other criteria as of March 31, 2020 and September 30, 2020: Consolidated VIEs Significant unconsolidated VIEs March 31, 2020 Consolidated assets Total assets Maximum exposure to (in billions of yen) Asset-backed commercial paper/loan programs 2,160 — — Asset-backed securitizations 572 77 7 Investments in securitization products 370 — — Investment funds 2,694 2,299 514 Trust arrangements and other 19 — — Total 5,815 2,376 521 Consolidated VIEs Significant unconsolidated VIEs September 30, 2020 Consolidated assets Total assets Maximum exposure to (in billions of yen) Asset-backed commercial paper/loan programs 2,045 — — Asset-backed securitizations 780 77 8 Investments in securitization products 370 — — Investment funds 2,283 2,346 483 Trust arrangements and other 5,557 — — Total 11,035 2,423 491 As of March 31, 2020 and September 30, 2020, the noncontrolling interests in consolidated VIEs amounted to ¥541 billion and ¥ 275 The Group has not provided financial or other support to consolidated or unconsolidated VIEs that the Group was not previously contractually required to provide. The tables below present the carrying amounts and classification of assets and liabilities on the MHFG Group’s balance sheets that relate to its variable interests in significant unconsolidated VIEs, as of March 31, 2020 and September 30, 2020: Assets on balance sheets related to unconsolidated VIEs: March 31, 2020 September 30, 2020 (in billions of yen) Trading account assets 108 113 Investments 267 231 Loans 55 58 Total 430 402 Liabilities on balance sheets and maximum exposure to loss related to unconsolidated VIEs: March 31, 2020 September 30, 2020 (in billions of yen) Payables under securities lending transactions 47 48 Trading account liabilities 2 2 Total 49 50 Maximum exposure to loss (Note) 521 491 Note: This represents the maximum amount the Group could possibly be required to record in its consolidated statements of income associated with on-balance-sheet off-balance-sheet In the table above the nature of the Group’s variable interest can take different forms, as described further in the notes below. Additionally the Group’s exposure to the obligations of VIEs is generally limited to its interest in these entities. In certain instances the Group provides undrawn commitments to the VIEs. The Group’s maximum exposure to loss presented in the table above does not include the benefit of offsetting financial instruments that are held to mitigate the risks associated with these variable interests. Furthermore, the Group’s maximum exposure to loss presented in the table above is not reduced by the amount of collateral held as part of the transaction with the VIE or any party to the VIE directly against a specific exposure to loss. Asset-backed commercial paper/loan programs The MHFG Group manages several asset-backed commercial paper/loan programs that provide its clients with off-balance-sheet Asset-backed securitizations The MHFG Group acts as an arranger of various types of structured finance schemes to meet its clients’ needs for off- balance In addition, the MHFG Group establishes several single-issue and multi-issue special purpose entities that issue collateralized debt obligations (“CDO”) or CLO, synthetic CDO/CLO or other repackaged instruments to meet clients’ and investors’ financial needs. The MHFG Group also arranges securitization transactions including CMBS, RMBS and others. In these transactions, the MHFG Group acts as an underwriter, placement agent, asset manager, derivatives counterparty, and/or investor in debt and equity instruments. In these cases, the MHFG Group consider that these variable interests are not significant as the MHFG Group does not have material balance sheet or off-balance tax-exempt Investments in securitization products The MHFG Group invests in, among other things, various types of CDO/CLO, synthetic CDO/CLO and repackaged instruments, CMBS and RMBS arranged by third parties for the purpose of generating current income or capital appreciation, which all utilize entities that are deemed to be VIEs. By design, such investments were investment grade at issuance and held by a diverse group of investors. The potential loss amounts of the securities and the loans are generally limited to the amounts invested because the Group has no contractual involvement in such VIEs beyond its investments. Since the Group is involved in these VIEs only as an investor, the Group does not ordinarily have the power to direct the VIEs’ activities that most significantly impact the VIEs’ economic performance. Similar to the criteria noted in the asset-backed securitization section, the Group views this investment activity to be “significant” when it has a large investment share and/or provides loans to the VIEs. The Group consolidates VIEs, where the transactions are tailored by the third party arrangers to meet the Group’s needs as a main investor, who is ultimately deemed to have the power to determine which assets are to be held by the VIEs. The Group also invests in certain beneficial interests issued by VIEs which hold real estate that the Group utilizes. In addition to these variable interests, when the Group has the power including the sole unilateral ability to liquidate the VIEs, the Group consolidates such VIEs. Investment funds The MHFG Group invests in various investment funds, including securities investment trusts, which collectively invest in equity and debt securities that include listed Japanese securities and investment grade bonds. Investment advisory companies or fund management companies, including the Group’s subsidiaries and affiliates, administer and make investment decisions about such investment funds. The Group considers that it is a “significant” variable interest when the Group’s investment share is greater than threshold. The Group consolidates certain investment funds where it is deemed to be the primary beneficiary. The Group determines whether it is the primary beneficiary by evaluating whether it has both (1) the power to make investment decisions about the investment funds and (2) the obligation to absorb losses or the right to receive benefits that could potentially be significant to the investment funds. The Group consolidates certain investment funds where it is deemed to be the primary beneficiary. Trust arrangements The MHFG Group offers a variety of asset management and administration services under trust arrangements including security investment trusts, pension trusts and trusts used in the securitization of assets originated by and transferred to third parties. The Group receives trust fees for providing services as an agent or fiduciary on behalf of beneficiaries. In these cases, the MHFG Group considers that these variable interests are not significant other than specific involvements such as the following; With respect to guaranteed principal money trust products, the MHFG Group assumes certain risks by providing guarantees for the repayment of principal as required by the trust agreements or relevant Japanese legislation. The MHFG Group manages entrusted funds primarily through the origination of high quality loans and other credit-related products, investing in investment grade marketable securities such as Japanese government bonds and placing cash with the MHFG Group’s subsidiary trust banks. The Group has the power to determine which assets will be held by the VIEs or to manage these assets. In addition, through the principal guarantee agreements, the Group has the obligation to absorb losses that could potentially be significant to the VIEs. Therefore, the Group consolidates such VIEs. However, the MHFG Group does not consolidate certain guaranteed principal money trusts, which invest all the entrusted funds in the MHFG Group itself, as the Group has determined that it has no variable interests. See Note 14 “Commitments and contingencies” for the balances of guaranteed trust principal that are not consolidated at March 31, 2020 and September 30, 2020. With respect to non-guaranteed non-guaranteed The MHFG Group has established a trust in August 2020 , which holds the Group’s housing loans and in turn issues beneficiary interests to the Group, as a result from Special Funds-Supplying Operations implemented by the Bank of Japan to facilitate financing in response to COVID-19. Special purpose entities created for structured finance The MHFG Group is involved in real estate, commercial aircraft and other vessel and machinery and equipment financing to VIEs and financing in securitized receivable. As the Group typically only provides senior financing with credit enhanced by subordinated interests and may sometimes act as an interest rate swap counterparty, the Group has determined that it does not have the power to direct the activities of the VIEs that most significantly impact the VIEs’ economic performance, or it does not have significant variable interests. Therefore, the Group does not consolidate such VIEs. Funding Vehicles The MHFG Group has established several wholly-owned off-shore 317 Securitization The MHFG Group engages in securitization activities and securitizes mortgage loans, other loans, government and corporate securities and other types of financial assets in the normal course of business. In these securitization transactions, the Group records the transfer of a financial asset as a sale when all the accounting criteria for a sale under ASC 860, “Transfers and Servicing” (“ASC860”) are met. These criteria are (1) the transferred financial assets are legally isolated from the Group’s creditors, (2) the transferee or beneficial interest holder has the right to pledge or exchange the transferred financial assets, and (3) the Group does not maintain effective control over the transferred financial assets. If all the criteria are not met, the transfer is accounted for as a secured borrowing. For the six months ended September 30, 2019 and 2020, the MHFG Group neither made significant transfers of financial assets nor recognized significant gains or losses in securitization transactions accounted for as sales. The Group did not retain significant interests in securitization transactions accounted for as sales as of March 31, 20 20 There are certain transactions where transfers of financial assets do not qualify for the aforementioned sales criteria and are accounted for as secured borrowings. These transferred assets continue to be carried on the consolidated balance sheets of the MHFG Group. Such assets are associated with securitization transactions and loan participation transactions, which amounted to ¥176 billion and ¥153 billion as of March 31, 2020, and ¥ 174 ¥ 142

Noninterest income

Noninterest income	6 Months Ended
	Sep. 30, 2020
Noninterest income	16. Noninterest income Details of Noninterest income for t Six months ended September 30, 2019 2020 (in millions of yen) Fee and commission income: Securities-related business (1) 64,498 78,441 Deposits-related business (1) 7,570 7,408 Lending-related business (2)(4) 68,609 79,619 Remittance business (1) 56,075 54,785 Asset management business (1) 48,291 45,948 Trust-related business (1) 56,459 54,425 Agency business (1) 15,152 15,064 Guarantee-related business (3) 13,898 15,560 Fees for other customer services (1) 73,440 77,067 Total Fee and commission income 403,992 428,317 Foreign exchange gains (losses)—net (3) 27,923 22,785 Trading account gains (losses)—net (2) 395,405 257,591 Investment gains (losses)—net: Debt securities (3) 31,092 46 Equity securities (3) (126,648 ) 266,119 Equity in earnings (losses) of equity method investees-net (3) 22,066 5,788 Gains on disposal of premises and equipment (3) 1,693 6,849 Other noninterest income (2)(5) 34,839 23,715 Total 790,362 1,011,210 Notes: (1) These amounts are revenues from contracts within the scope of ASC 606, “Revenue from contracts with customers” (“ASC 606”). (2) Part of these amounts are considered to be revenues from contracts that are within the scope of ASC 606. (3) These amounts are revenues from contracts that do not meet the scope of ASC 606. (4) Most of the lending-related fees such as commitment fees and arrangement fees are not within the scope of ASC 606. (5) These amounts include the net unrealized gains resulting from changes in fair values of structured notes that contain embedded derivatives. See Note 17 “Fair value” for further details. Certain Fee and commission income, Trading account gains (losses)-net Fee and commission income For the MHFG Group’s accounting policy for the recognition of Fee and commission income, see Note 1 “Basis of presentation and summary of significant accounting policies” to the consolidated financial statements in the Group’s most recent Form 20-F. Trust-related business fees consist of trust fees earned primarily through fiduciary asset management and administrative service and other trust-related fees, which amounted to ¥25 billion and ¥31 billion for the six months ended September 30, 2019, respectively, and ¥25 billion and ¥29 billion for the six months ended September 30, 2020, respectively. Trading account gains (losses)—net and Other noninterest income In addition to Fee and commission income, Trading account gains (losses)-net and Trading account gains (losses)-net. Underwriting Contract balances relating to revenues from contracts with customers subject to ASC 606 Contract assets and receivables from contracts with customers subject to ASC 606 are recognized in Accrued income or accounts receivable of Other assets. As of March 31, 2020 and September 30, 2020, the balance of contract assets was not material. Contract liabilities are recognized in unearned income of Other liabilities. As of March 31, 2020 and September 30, 2020, the balance of contract liabilities was not material. Remaining performance obligations relating to revenues from contracts with customers subject to ASC 606 Remaining performance obligations are services that the MHFG Group has committed to provide in the future in connection with its contracts with customers. As of March 31, 2020 and September 30, 2020, the amount of expected revenues from current obligations to provide services in the future was not material. It excludes revenues from contracts less than one year or contracts that have provisions that allow the Group to recognize revenue at the amount it has the right to invoice.

Fair value

Fair value	6 Months Ended
	Sep. 30, 2020
Fair value	17. Fair value Fair value measurements ASC 820, “Fair Value Measurements” (“ASC 820”), defines fair value as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. ASC 820 also establishes a fair value hierarchy which requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. In addition, ASC 820 precludes (1) the deferral of gains and losses at inception of certain derivative contracts whose fair value was not evidenced by market-observable data, and (2) the use of block discounts when measuring the fair value of instruments traded in an active market, which were previously applied to large holdings of publicly traded financial instruments. Fair value hierarchy ASC 820 specifies a hierarchy of valuatio n Level 1 Quoted prices in active markets for identical assets or liabilities. Level 1 assets and liabilities include debt and equity securities and derivative contracts that are traded in an active exchange market. Level 2 Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 2 assets and liabilities include debt securities with quoted prices that are traded less frequently than exchange-traded instruments. If no quoted market prices are available, the fair values of debt securities and over-the-counter Level 3 Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. Level 3 assets and liabilities include financial instruments whose values are determined using pricing models, discounted cash flow methodologies, or similar techniques, as well as instruments for which the determination of fair value requires significant management judgment or estimation. Valuation process The MHFG Group has established valuation policies which govern the principles of fair value measurements and the authority and duty of each department. The Group has also established procedure manuals which describe valuation techniques and related inputs for determining the fair values of various financial instruments. The policies require that the measurement of fair values be carried out in accordance with the procedures performed by the risk management departments or the back offices which are independent from the front offices. The policies also require the risk management departments to check and verify whether the valuation methodologies defined in the procedure manuals are fair and proper and the internal audit departments to periodically review the compliance with the procedures throughout the Group. Although the valuation methodologies and related inputs are consistently used from period to period, a change in the market environment sometimes leads to a change in the valuation methodologies and the inputs. For instance, a change in market liquidity due to a delisting or a new listing is one of the key drivers of revisions to the valuation methodologies and the inputs. The key drivers also include the availability or the lack of market observable inputs and the development of new valuation methodologies. Price verification performed through the Group’s internal valuation process has an important role in identifying whether the valuation methodologies and the inputs need to be changed. The internal valuation process over the prices broker-dealers provide, primarily for Japanese securitization products, is described in more detail below in Available-for-sale The following is a description of valuation methodologies and inputs used for assets and liabilities measured at fair value on a recurring basis, including the general classification of such instruments pursuant to the fair value hierarchy and the MHFG Group’s valuation techniques used to measure fair values. During the six months ended September 30, 2020, there were no significant changes made to the Group’s valuation techniques and related inputs. Trading securities and trading securities sold, not yet purchased When quoted prices for identical securities are available in an active market, the Group uses the quoted prices to measure the fair values of securities and such securities are classified in Level 1 of the fair value hierarchy. Level 1 securities include highly liquid government bonds and equity securities. When quoted prices for identical securities are available, but not actively traded, such securities are classified in Level 2 of the fair value hierarchy. When no quoted market prices are available, the Group estimates fair values by using pricing models with inputs that are observable in the market and such securities are classified in Level 2 of the fair value hierarchy. Level 2 securities include Japanese local government bonds, corporate bonds, and commercial paper. When less liquid market conditions exist for securities, the quoted prices are stale or the prices from independent sources vary significantly, such securities are generally classified in Level 3 of the fair value hierarchy. The fair values of securitization products such as RMBS, CMBS, ABS, and CLO are determined primarily by using a discounted cash flow model. The key inputs used for the model include default rates, recovery rates, prepayment rates, and discount rates. In the event that certain key inputs are unobservable or cannot be corroborated by observable market data, these financial instruments are classified in Level 3. Hedge funds the Group invests in are primarily multi strategy funds that employ a fundamental bottom-up start-up ten-year Derivative financial instruments Exchange-traded derivatives are valued using quoted market prices and consequently are classified in Level 1 of the fair value hierarchy. However, the majority of derivatives entered into by the Group are executed over-the-counter over-the-counter severity factors that are developed from market credit spreads a over-the-counter Available-for-sale The fair values of available-for-sale non-binding Equity securities Equity securities mainly consist of marketable equity securities. The fair values of the marketable equity securities are based upon quoted market prices for identical equity securities trading as securities in an active market. Equity securities also include investments in certain investment funds measured using the NAV per share practical expedient including private equity funds and real estate funds. These securities are determined primarily using the same procedures described under Trading securities and trading securities sold, not yet purchased Other investments Other investments consist of investments held by consolidated investment companies. These companies typically hold investments in marketable and non-marketable non-marketable such securities, the Group firstly considers recent market transactions of identical securities, if applicable. Thereafter, the Group uses commonly accepted valuation techniques such as earnings multiples based on comparable public securities. Non-marketable Long-term debt Fair value accounting is elected for certain long-term debt instruments with embedded derivatives. The fair values are determined using a discounted cash flow model that considers the embedded derivatives and the terms and payment structures of the notes. The fair values of the derivatives embedded in such notes are primarily derived by using the same procedures described in Derivative financial instruments Items measured at fair value on a recurring basis Assets and liabilities measured at fair valu e March 31, 2020 Level 1 Level 2 Level 3 Assets/ Liabilities measured at fair value (in billions of yen) Assets: Trading securities (1) Japanese government bonds 1,516 22 — 1,538 Japanese local government bonds — 170 — 170 U.S. Treasury bonds and federal agency securities 4,580 461 — 5,041 Other foreign government bonds 1,128 547 — 1,675 Agency mortgage-backed securities — 3,390 — 3,390 Residential mortgage-backed securities — — 10 10 Certificates of deposit and commercial paper — 1,036 — 1,036 Corporate bonds and other (2) 41 1,398 1,115 2,554 Equity securities 1,000 650 30 1,680 Trading securities measured at net asset value (3) 462 Derivative financial instruments: Interest rate contracts 153 7,070 9 7,232 Foreign exchange contracts 9 2,900 17 2,926 Equity-related contracts 169 125 16 310 Credit-related contracts — 22 8 30 Other contracts 3 11 24 38 Available-for-sale Japanese government bonds 11,950 653 — 12,603 Japanese local government bonds — 273 — 273 U.S. Treasury bonds and federal agency securities 935 — — 935 Other foreign government bonds 436 975 — 1,411 Agency mortgage-backed securities — 505 — 505 Residential mortgage-backed securities — 53 31 84 Commercial mortgage-backed securities — — 615 615 Japanese corporate bonds and other debt securities — 1,678 157 1,835 Foreign corporate bonds and other debt securities — 678 174 852 Equity securities: Equity securities with readily determinable fair values 2,670 95 — 2,765 Equity securities measured at net asset value (3) 72 Other investments — — 39 39 Total assets measured at fair value on a recurring basis 24,590 22,712 2,245 50,081 Liabilities: Trading securities sold, not yet purchased 1,880 515 — 2,395 Derivative financial instruments: Interest rate contracts 163 6,611 14 6,788 Foreign exchange contracts 8 2,890 1 2,899 Equity-related contracts 186 47 33 266 Credit-related contracts — 19 10 29 Other contracts 6 10 23 39 Long-term debt (4) — 1,916 621 2,537 Total liabilities measured at fair value on a recurring basis 2,243 12,008 702 14,953 September 30, 2020 Level 1 Level 2 Level 3 Assets/ Liabilities measured at fair value (in billions of yen) Assets: Trading securities (1) Japanese government bonds 3,257 11 — 3,268 Japanese local government bonds — 138 — 138 U.S. Treasury bonds and federal agency securities 4,963 829 — 5,792 Other foreign government bonds 938 526 — 1,464 Agency mortgage-backed securities — 4,348 — 4,348 Residential mortgage-backed securities — — 9 9 Certificates of deposit and commercial paper — 1,259 — 1,259 Corporate bonds and other (2) 22 1,348 1,085 2,455 Equity securities 929 570 30 1,529 Trading securities measured at net asset value (3) 447 Derivative financial instruments: Interest rate contracts 40 6,088 7 6,135 Foreign exchange contracts — 2,123 20 2,143 Equity-related contracts 98 287 12 397 Credit-related contracts — 52 3 55 Other contracts 3 10 15 28 Available-for-sale Japanese government bonds 19,600 320 — 19,920 Japanese local government bonds — 407 — 407 U.S. Treasury bonds and federal agency securities 627 — — 627 Other foreign government bonds 430 926 — 1,356 Agency mortgage-backed securities — 520 — 520 Residential mortgage-backed securities — 53 27 80 Commercial mortgage-backed securities — — 641 641 Japanese corporate bonds and other debt securities — 1,579 491 2,070 Foreign corporate bonds and other debt securities — 747 178 925 Equity securities: Equity securities with readily determinable fair values 2,976 40 — 3,016 Equity securities measured at net asset value (3) 83 Other investments — — 56 56 Total assets measured at fair value on a recurring basis 33,883 22,181 2,574 59,168 Liabilities: Trading securities sold, not yet purchased 2,051 268 20 2,339 Derivative financial instruments: Interest rate contracts 39 5,679 10 5,728 Foreign exchange contracts — 2,159 1 2,160 Equity-related contracts 128 109 23 260 Credit-related contracts — 75 2 77 Other contracts 4 8 14 26 Long-term debt (4) — 2,164 638 2,802 Total liabilities measured at fair value on a recurring basis 2,222 10,462 708 13,392 Notes: (1) Trading securities include foreign currency denominated s (2) The amount includes CLO and convertible bonds, which are classified in Level 3. (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, 2020 and September 30, 2020 were ¥47 billion and ¥ 56 (4) Amounts represent items for which the Group elected the fair value option or for which it applied the practicability exception. Items measured at fair value on a recurring basis using significant unobservable inputs (Level 3) The following table presents a reconciliation for all assets and liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) for the six months ended September 30, 2019 and 2020: Six months ended September 30, 2019 April 1, 2019 Gains (losses) in Earnings Gains (losses) in OCI Transfers into Level 3 Transfers out of Level 3 Purchases Sales Issuances Settle- ments September 30, 2019 Change in unrealized gains (losses) still held (6) (in billions of yen) Assets: Trading securities: Residential mortgage-backed securities 11 — (2) — — — — — — (1 ) 10 — Corporate bonds and other 1,044 (15 ) (2) — — — 338 (105 ) — (125 ) 1,137 (14 ) Equity securities 28 2 (2) — — — 1 — — (1 ) 30 — Derivative financial instruments, net (1) Interest rate contracts 13 (9 ) (2) — — — — — — 1 5 (8 ) Foreign exchange contracts 22 (10 ) (2) — — — — — — (2 ) 10 (9 ) Equity-related contracts (5 ) 1 (2) — — — — — — (3 ) (7 ) 2 Credit-related contracts 1 — (2) — — — — — — — 1 — Other contracts 1 — (2) — — — — — — — 1 — Available-for-sale Residential mortgage-backed securities 40 — (3) — (4) — — — — — (7 ) 33 — Commercial mortgage-backed securities 500 — (3) 1 (4) — — 89 (35 ) — (6 ) 549 — Japanese corporate bonds and other 120 1 (3) 4 (4) — — 97 — — (53 ) 169 — Foreign corporate bonds and other debt securities 103 — (3) (5 ) (4) — — 38 — — (3 ) 133 — Other investments 35 1 (3) — — — 10 — — (10 ) 36 2 Liabilities: Trading securities sold, not yet purchased 1 — (2) — — — (9 ) 8 — — — — Long-term debt 655 (6 ) (5) — (4) 17 (6 ) — — 108 (134 ) 646 (10 ) Six months ended September 30, 2020 April 1, 2020 Gains (losses) Earnings Gains (losses) OCI Transfers into Level 3 Transfers out of Level 3 Purchases Sales Issuances Settle- ments September 30, 2020 Change in unrealized gains (losses) still held (6) (in billions of yen) Assets: Trading securities: Residential mortgage-backed securities 10 — (2) — — — — — — (1 ) 9 — Corporate bonds and other 1,115 18 (2) — — (1 ) 189 (113 ) — (123 ) 1,085 18 Equity securities 30 (2 ) (2) — — — 2 — — — 30 (1 ) Derivative financial instruments, net (1) Interest rate contracts (5 ) (3 ) (2) — — — — — — 5 (3 ) 1 Foreign exchange contracts 16 4 (2) — — — — — — (1 ) 19 5 Equity-related contracts (17 ) 4 (2) — — — — — — 2 (11 ) 3 Credit-related contracts (2 ) 3 (2) — 1 1 — — — (2 ) 1 1 Other contracts 1 — (2) — — — — — — — 1 — Available-for-sale Residential mortgage-backed securities 31 — (3) — (4) — — — — — (4 ) 27 — Commercial mortgage-backed securities 615 — (3) 1 (4) — — 78 (51 ) — (2 ) 641 — Japanese corporate bonds and other debt securities 157 (7 ) (3) 8 (4) — — 344 — — (11 ) 491 — Foreign corporate bonds and other debt securities 174 1 (3) 8 (4) — — 31 — — (36 ) 178 — Other investments 39 (1 ) (3) — — — 38 (1 ) — (19 ) 56 (1 ) Liabilities: Trading securities sold, not yet purchased — — (2) — — — — 20 — — 20 — Long-term debt 621 (37 ) (5) (8 ) (4) 19 (35 ) — — 108 (120 ) 638 (27 ) Notes: (1) Total Level 3 derivative exposures have been netted on the table for presentation purposes only. (2) Gains (losses) in Earnings are reported in Trading account gains (losses)-net, (losses)-net (3) Gains (losses) in Earnings are reported in Investment gains (losses)-net. (4) Gains (losses) in OCI are reported in Other comprehensive income (loss). (5) Gains (losses) in Earnings are reported in Other noninterest income (expenses). (6) 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 September 30, 2019 and 2020. The amounts of unrealized gains (losses) in OCI related to Available-for-sale securities and Long-term debt were ¥7 billion and ¥(8) billion, at September 30, 2020, respectively. Transfers between levels During the six months ended September 30, 2019, the transfers into Level 3 included ¥17 billion of Long-term debt. Transfers into Level 3 for Long-term debt were primarily due to changes in the observability of the default rate when valuing certain structured notes. During the six months ended September 30, 2019, the transfers out of Level 3 included billion of Long-term debt. Transfers out of Level 3 for Long-term debt were primarily due to changes in the observability of the default rate when valuing certain structured notes. During the six months ended September 30, 2020, the transfers into Level 3 included ¥1 billion of net Derivative assets and billion of Long-term debt. Transfers into Level 3 for net Derivative assets were primarily due to changes in the observability of the inputs used to measure fair value of certain credit-related derivatives. Transfers into Level 3 for Long-term debt were primarily due to changes in the observability of the default rate when valuing certain structured notes. During the six months ended September 30, 2020, the transfers out of Level 3 included ¥1 billion of Trading securities, ¥1 billion of net Derivative liabilities and Quantitative information about Level 3 fair value measurements The following table presents information about significant unobservable inputs related to the MHFG Group’s material classes of Level 3 assets and liabilities at March 31, 2020 and September 30, 2020: March 31, 2020 Products/Instruments Fair value Principal valuation technique Unobservable inputs Range of input values Weighted average (5) (in billions of yen, except for percentages and basis points) Trading securities and Available-for-sale Residential mortgage-backed securities 41 Discounted cash flow Price-based Prepayment rate Default rate Recovery rate Discount margin 4% - 16% 0% - 1% 100% - 100% 5bps - 170bps 7% 0% 100% 52bps Commercial mortgage-backed securities 615 Discounted cash flow Price-based Discount margin 7bps - 185bps 22bps Corporate bonds and other debt securities 1,446 Discounted cash flow Price-based Prepayment rate (1) Default rate (1) Recovery rate (1) Discount margin (1) Discount margin (2) 13% - 21% 0% - 2% 10% - 70% 61bps - 1,160bps 5bps - 1,528bps 21% 2% 67% 256bps 58bps Derivative financial instruments, net: Interest rate contracts (5 ) Internal valuation model (3) IR – IR correlation Default rate (4) 23% - 100% 0% - 63% Foreign exchange contracts 16 Internal valuation model (3) FX – IR correlation FX – FX correlation Default rate (4) -37% - 49% 56% - 65% 0% - 63% Equity-related contracts (17 ) Internal valuation model (3) Equity – IR correlation Equity correlation Equity volatility 25% - 25% 0% - 100% 13% - 157% Credit-related contracts (2 ) Internal valuation model (3) Default rate Credit correlation 0% - 15% 30% - 100% Long-term debt 621 Internal valuation model (3) IR – IR correlation FX – IR correlation FX – FX correlation Equity – IR correlation Equity – FX correlation Equity correlation Equity volatility Default rate Credit correlation 23% - 100% -37% - 50% 56% - 65% 25% - 25% -33% - 100% 0% - 100% 15% - 157% 0% - 12% 15% - 100% September 30, 2020 Products/Instruments Fair value Principal valuation technique Unobservable inputs Range of input values Average (5) (in billions of yen, except for percentages and basis points) Trading securities and Available-for-sale securities: Residential mortgage-backed securities 36 Discounted cash flow Price-based Prepayment rate Default rate Recovery rate Discount margin 3% - 16% 0% - 1% 100% - 100% 5bps - 170bps 7% 0% 100% 50bps Commercial mortgage-backed securities 641 Discounted cash flow Price-based Discount margin 6bps - 185bps 21bps Corporate bonds and other debt securities 1,754 Discounted cash flow Price-based Prepayment rate (1) Default rate (1) Recovery rate (1) Discount margin (1) Discount margin (2) 1% - 22% 0% - 3% 10% - 69% 25bps - 173bps 4bps - 696bps 19% 1% 67% 123bps 233bps Derivative financial instruments, net: Interest rate contracts (3) Internal valuation model (3) IR - IR correlation 23% - 100% 76% Foreign exchange contracts 19 Internal valuation model (3) FX - IR correlation FX - FX correlation -27% -52% 46% - 63% 28% 55% Equity-related contracts (11) Internal valuation model (3) Equity - IR correlation Equity correlation Equity volatility 25% - 25% 0% - 100% 12% - 96% 25% 88% 43% Credit-related contracts 1 Internal valuation model (3) Default rate Credit correlation 0% - 7% 35% - 100% 1% 66% Other contracts 1 Internal valuation model (3) Commodity volatility 0% - 57% 36% Long-term debt 638 Internal valuation model (3) IR - IR correlation FX - IR correlation FX - FX correlation Equity - IR correlation Equity - FX correlation Equity correlation Equity volatility Default rate Credit correlation 23% - 100% -27% - 52% 46% - 63% 25% - 25% -33% - 100% 0% - 100% 13% - 96% 0% - 6% 18% - 100% 76% 35% 55% 25% -3% 86% 29% 2% 66% Notes: (1) These inputs are mainly used for determining the fair values of securitization products such as CDO, CLO and ABS, other than RMBS and CMBS. (2) This input is mainly used for determining the fair values of Japanese corporate bonds and foreign corporate bonds. (3) Internal valuation model includes discounted cash flow models and the Black-Scholes option pricing model. (4) This input represents the counterparty default rate derived from the MHFG Group’s own internal credit analyses. (5) 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. IR = Interest rate FX = Foreign exchange Uncertainty of fair value measurements relating to unobservable inputs and interrelationships among unobservable inputs The following is a description of the uncertainty of the fair value measurements from the use of significant unobservable inputs and a description of interrelationships of the significant unobservable inputs used to measure the fair values of Level 3 assets and liabilities. (1) Prepayment rate The prepayment rate is the estimated rate at which voluntary unscheduled repayments of the principal of the underlying assets are expected to occur. The movement of the prepayment rate is generally negatively correlated with borrower delinquency. A change in prepayment rate would impact the valuation of the fair values of financial instruments either positively or negatively, depending on the structure of financial instruments. (2) Default rate The default rate is an estimate of the likelihood of not collecting contractual payments. An increase in the default rate would generally be accompanied by a decrease in the recovery rate and an increase in the discount margin. It would also generally impact the valuation of the fair values of financial instruments negatively. (3) Recovery rate The recovery rate is an estimate of the percentage of contractual payments that would be collected in the event of a default. An increase in recovery rate would generally be accompanied by a decrease in the default rate. It would also generally impact the valuation of the fair values of financial instruments positively. (4) Discount margin The discount margin is the portion o (5) Correlation Correlation is the likelihood of the movement of one input relative to another based on an established relationship. The change in correlation would impact the valuation of derivatives either positively or negatively, depending on the nature of the underlying assets. (6) Volatility Volatility is a measure of the expected change in variables over a fixed period of time. Some financial instruments benefit from an increase in volatility and others benefit from a decrease in volatility. Generally, for a long position in an option, an increase in volatility would result in an increase in the fair values of financial instruments. Items measured at fair value on a nonrecurring basis Certain assets and liabilities are measured at fair value on a nonrecurring basis. These assets and liabilities primarily include items that are measured at the lower of cost or fair value, and items that were initially measured at cost and have been written down to fair value as a result of impairment. The following table shows the fair value hierarchy for these items as of March 31, 2020 and September 30, 2020: March 31, 2020 Total Level 1 Level 2 Level 3 Aggregate (in billions of yen) Assets: Loans 90 — — 90 136 Loans held-for-sale 26 — 20 6 26 Equity securities (without readily determinable fair values) 2 — — 2 2 Premises and equipment - 1 — 1 — 12 Other assets — — — — 3 Goodwill — — — — 2 Total assets measured at fair value on a nonrecurring basis 119 — 21 98 181 September 30, 2020 Total Level 1 Level 2 Level 3 Aggregate (in billions of yen) Assets: Loans 131 — 2 129 200 Loans held-for-sale 17 — 11 6 18 Equity securities (without readily determinable fair values) 1 — — 1 2 Other investment s 52 31 — 21 59 Premises and equipment - — — — — 1 Total assets measured at fair value on a nonrecurring basis 201 31 13 157 280 Note: The fair values may not be current as of the dates indicated, but rather as of the date the fair value change occurred. Accordingly, the carrying values may not equal current fair value. Loans in the table above became nonaccrual and are measured based upon the observable market price of the loan or the fair value of the underlying collateral. Loans held-for-sale Equity securities (without readily determinable fair values) in the table above consist of non-marketable equity securities which are measured at fair value on a nonrecurring basis, using the measurement alternative for non-marketable equity securities. These equity securities are on a nonrecurring basis either (1) written down to fair value as a result of impairment or (2) adjusted upward or downward to fair value as a result of transactions observed for the identical or similar securities of the same issuer. The fair values of the impaired non-marketable equity securities are determined primarily by using a liquidation value technique. As significant management judgment or estimation is required in the determination of the fair values of non-marketable equity securities, they are classified as Level 3. Other investments in the table above include certain equity method investments which have been impaired and written down to fair value. The fair values of the impaired marketable equity method investments are determined by their quoted market prices. As the securities are traded on an active exchange market, they are classified as Level 1. The fair values of the impaired non-marketable equity method investments are determined primarily by using a discounted cash flow model. As significant management judgment or estimation is required in the determination of the fair values of non-marketable equity method investments, they are classified as Level 3. There were no other investments measured at fair value on a nonrecurring basis as of March 31, 2020. Premises and equipment–net and Other assets in the table above have been impaired and written down to fair value. Goodwill in the table above is due to the decline in the fair value of the reporting unit, the carrying amount of the goodwill was reduced to its fair value. There was no goodwill measured at fair value on a nonrecurring basis as of September 30, 2020. Fair value option The MHFG Group elected the fair value option for certain eligible financial instruments described below. Foreign currency denominated debt securities The MHFG Group elected the fair value option for foreign currency denominated debt securities to mitigate the volatility in earnings due to the difference in the recognition of foreign exchange risk between foreign currency denominated debt securities and financial liabilities. Following the election of the fair value option, these debt securities are reported as trading securities in Trading account assets. Certain hybrid financial instruments The MHFG Group issues structured notes as part o billion at March 31, 2020 and September 30, 2020, respectively. The net unrealized gains (losses) resulting from changes in fair values of these notes recorded in Other noninterest income (expenses) were of ¥2 billion and ¥ 17 billion for the six months ended September 30, 2019 and 2020, respectively. Changes in fair value resulting from changes in instrument-specific credit risk were estimated by incorporating the Company’s current credit spreads observable in the bond market. Fair value of financial instruments ASC 825, “Financial Instruments” (“ASC 825”), requires the disclosure of the estimated fair value of financial instruments. The fair value of financial instruments is the amount that would be exchanged between willing parties, other than in a forced sale or liquidation. Quoted market prices, if available, are best utilized as estimates of the fair values of financial instruments. However, since no quoted market prices are available for certain financial instruments, fair values for such financial instruments have been estimated based on management’s The following is a description of the valuation methodologies used for estimating the fair value of financial assets and liabilities not carried at fair value on the MHFG Group’s consolidated balance sheets. Cash and due from banks, interest-bearing deposits in other banks, call loans and funds sold, and receivables under resale agreements and securities borrowing transactions The carrying value of short-term financial assets, such as cash and due from banks, interest-bearing deposits in other banks, call loans and funds sold, and receivables under resale agreements and securities borrowing transactions approximates the fair value of these assets since they generally involve limited losses from credit risk or have short-term maturities with interest rates that approximate market rates. Investments The fair value of held-to-maturity available-for-sale non-marketable billion and ¥402 billion Loans Loans have been fair valued based on the type of loan, credit quality, prepayment assumptions and remaining maturity. The fair value of loans is determined based on discounted cash flows using interest rates approximating the MHFG Group’s current rates for similar loans. The fair value of collateral dependent nonaccrual loans is determined based on the fair value of the underlying collateral. Other financial assets The carrying value of other financial assets, which primarily consist of accounts receivable from brokers, dealers, and customers for securities transactions, accrued income and collateral provided for derivative transactions, approximates the fair value of these assets since they generally involve limited losses from credit risk or have short-term maturities with interest rates that approximate market rates. The majority of other financial assets is classified as Level 2, and included in the table in Note 6 “Other assets and liabilities.” Noninterest-bearing deposits, call money and funds purchased, and payables under repurchase agreements and securities lending transactions The carrying value of short-term financial liabilities, such as noninterest-bearing deposits, call money and funds purchased, and payables under repurchase agreements and securities lending transactions approximates the fair value of these liabilities since they generally have short-term maturities with interest rates that approximate market rates. Interest-bearing deposits The carrying value of demand deposits approximates the fair value since it represents the amount payable on demand at the balance sheet date. The fair value of time deposits and certificates of deposit is primarily estimated based on discounted cash flow analysis using current interest rates for instruments with similar maturities. The carrying value of short-term certificates of deposit approximates the fair value. Due to tru

Offsetting of financial assets

Offsetting of financial assets and financial liabilities	6 Months Ended
	Sep. 30, 2020
Offsetting of financial assets and financial liabilities	18. Offsetting of financial assets and financial liabilities Derivatives The MHFG Group enters into master netting arrangements such as International Swaps and Derivatives Association, Inc. (“ISDA”) or similar agreements with counterparties to manage mainly credit risks associated with counterparty default. If the predetermined events including counterparty default occur, these enforceable master netting arrangements or similar agreements give the Group the right to offset derivative receivables and derivative payables and related financial collateral such as cash and securities with the same counterparty. Repurchase and resale agreements and securities lending and borrowing transactions Repurchase and resale agreements and securities lending and borrowing transactions are generally covered by industry standard master repurchase agreements and industry standard master securities lending agreements with netting terms to manage mainly credit risks associated with counterparty default. In the event of default by the counterparty, these agreements with netting terms provide the Group with the right to offset receivables and payables related to such transactions with the same counterparty, and to liquidate the collateral held. The following table p Amounts not offset on the balance sheet (3) Gross amounts recognized Gross amounts offset on the balance sheet Net amounts presented on the balance sheet (2) Financial instruments (4) Cash collateral Net amounts (in billions of yen) March 31, 2020 Assets (1) Derivatives 9,819 — 9,819 (7,723 ) (629 ) 1,467 Receivables under resale agreements 17,347 — 17,347 (17,197 ) — 150 Receivables under securities borrowing transactions 1,753 — 1,753 (1,709 ) — 44 Total 28,919 — 28,919 (26,629 ) (629 ) 1,661 Liabilities (1) Derivatives 9,220 — 9,220 (7,519 ) (1,215 ) 486 Payables under repurchase agreements 17,542 — 17,542 (17,191 ) — 351 Payables under securities lending transactions 626 — 626 (623 ) — 3 Total 27,388 — 27,388 (25,333 ) (1,215 ) 840 September 30, 2020 Assets: Derivatives 8,758 — 8,758 ( 5 (6,373 ) (486 ) 1,899 Receivables under resale agreements 12,666 — 12,666 ( 6 (11,479 ) — 1,187 Receivables under securities borrowing transactions 2,186 — 2,186 ( 7 (1,846 ) — 340 Total 23,610 — 23,610 (19,698 ) (486 ) 3,426 Liabilities: Derivatives 8,251 — 8,251 ( 5 (6,148 ) (930 ) 1,173 Payables under repurchase agreements 19,326 — 19,326 ( 6 (18,038 ) — 1,288 Payables under securities lending 1,476 — 1,476 ( 7 (1,235 ) — 241 Total 29,053 — 29,053 (25,421 ) (930 ) 2,702 Notes: (1) 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. (2) Derivative assets and liabilities are recorded in Trading account assets and Trading account liabilities, respectively. (3) Amounts do not exceed the net amounts presented on the balance sheet and do not include the effect of overcollateralization, where it exists. (4) For derivatives, amounts include derivative assets or liabilities and securities collateral that are eligible for offsetting under enforceable master netting arrangements or similar agreements. (5) The amounts of derivative assets and liabilities subject to enforceable master netting arrangements or similar agreements at September 30, 2020 were ¥8,154 billion and ¥7,528 billion, respectively. (6) The amounts of Receivables under resale agreements and Payables under repurchase agreements subject to enforceable industry standard master repurchase agreements with netting terms at September 30, 2020 were ¥11,490 billion and ¥18,755 billion, respectively . (7) 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 at September 30, 2020 were ¥1,915 billion and ¥1,243 billion, respectively .

Repurchase agreements and secur

Repurchase agreements and securities lending transactions accounted for as secured borrowings	6 Months Ended
	Sep. 30, 2020
Repurchase agreements and securities lending transactions accounted for as secured borrowings	19. Repurchase agreements and securities lending transactions accounted for as secured borrowings The following table shows the gross amounts of liabilities associated with repurchase agreements and securities lending transactions, by remaining contractual maturity at March 31, 2020 and September 30, 2020: Overnight and continuous Up to 30 days 31-90 days Greater than 90 days Total (in billions of yen) March 31, 2020 Repurchase agreements 6,357 5,467 4,867 1,280 17,971 Securities lending transactions 877 231 — 316 1,424 Total 7,234 5,698 4,867 1,596 19,395 September 30, 2020 Repurchase agreements 10,154 3,684 3,162 2,326 19,326 Securities lending transactions 798 298 50 330 1,476 Total 10,952 3,982 3,212 2,656 20,802 The following table shows the gross amounts of liabilities associated with repurchase agreements and securities lending transactions, by class of underlying collateral at March 31, 2020 and September 30, 2020: Repurchase agreements Securities lending transactions (in billions of yen) March 31, 2020 Japanese government bonds and Japanese local government bonds 1,790 269 Foreign government bonds and foreign agency mortgage-backed securities 15,218 359 Commercial paper and corporate bonds 273 50 Equity securities 542 730 Other 148 16 Total (Note) 17,971 1,424 September 30, 2020 Japanese government bonds and Japanese local government bonds 3,355 372 Foreign government bonds and foreign agency mortgage-backed securities 15,100 368 Commercial paper and corporate bonds 209 53 Equity securities 579 668 Other 83 15 Total (Note) 19,326 1,476 Note: Amounts exceeded the gross amounts recognized in Note 18 “Offsetting of financial assets and financial liabilities” by ¥1,227 billion and ¥804 billion, at March 31, 2020 and September 30, 2020, respectively, which excluded the amounts relating to master netting agreements or similar agreements where the MHFG Group did not have the legal right of set-off The MHFG Group is required to post securities as collateral with a fair value equal to or in excess of the principal amount of the cash borrowed under repurchase agreements. For securities lending transactions, the Group receives collateral in the form of cash. These contracts involve risks, including (1) the counterparty may fail to return the securities at maturity and (2) the fair value of the securities posted may decline below the amount of the Group’s obligation and therefore the counterparty may require additional amounts. The Group attempts to mitigate these risks by entering into transactions mainly with central counterparty clearing houses which revalue assets and perform margin maintenance activities on a regular basis, diversifying the maturities and counterparties, and using mainly highly liquid securities. The amounts or composition of assets pledged as collateral for borrowings and for other purposes have not changed significantly since March 31, 2020, except for loans. Loans pledged as collateral at September 30, 2020 and March 31, 2020 accounted for approximately 5% and 2% of total assets, respectively. See Note 8 “Pledged assets and collateral” to the consolidated financial statements in our annual report on Form 20-F

Business segment information

Business segment information	6 Months Ended
	Sep. 30, 2020
Business segment information	20. Business segment information The MHFG Group consists of the following five in-house The services that each in-house Retail & Business Banking Company This company provides financial services for individual customers, small and medium-sized Corporate & Institutional Company This company provides financial services for large corporations, financial institutions and public corporations in Japan. Global Corporate Company This company provides financial services for Japanese overseas affiliated corporate customers and non-Japanese Global Markets Company This company invests in financial products with market Asset Management Company This company develops financial products and provides financial services that match the asset management needs of its wide range of customers from individuals to institutional investors. The reportable segment information, set forth below, is derived from the internal management reporting systems used by management to measure the performance of the Group’s operating segments. Management measures the performance of each of the operating segments in accordance with internal managerial accounting rules and practices. In addition, the format and information are presented primarily on the basis of Japanese GAAP. Therefore, they are not consistent with the consolidated financial statements prepared in accordance with U.S. GAAP. A reconciliation is provided for the total amount of all business segments’ “Net business profits (losses) + Net gains (losses) related to ETFs and others” with income before income tax expense under U.S. GAAP, and the total amount of all business segments’ “Fixed assets” with the total amount of Premises and equipment-net, right-of-use MHFG (Consolidated) Six months ended September 30, 2019 (1) Retail & Business Banking Company Corporate & Institutional Company Global Corporate Company Global Markets Company Asset Management Company Others (6) Total (in billions of yen) Gross profits + Net gains (losses) related to ETFs and others (2) 322.0 220.2 203.9 235.0 25.5 16.2 1,022.8 General and administrative expenses (3) 330.7 104.0 118.6 101.4 16.4 17.3 688.4 Equity in earnings (losses) of equity method investees—net 6.4 1.1 6.0 — 0.5 5.0 19.0 Amortization of goodwill and others 1.4 0.1 0.2 0.5 3.9 0.5 6.6 Others — — — — — (5.9 ) (5.9 ) Net business profits (losses) (4) (3.7 ) 117.2 91.1 133.1 5.7 (2.5 ) 340.9 Fixed assets (5) 508.2 208.4 160.1 92.8 0.1 732.0 1,701.6 MHFG Six months ended September 30, 2020 Retail & Business Banking Company Corporate & Institutional Company Global Corporate Company Global Markets Company Asset Management Company Others (6) Total (in billions of yen) Gross profits + Net gains (losses) related to ETFs and others (2) 307.4 234.2 222.6 291.5 23.6 14.0 1,093.3 General and administrative expenses (3) 315.0 104.6 121.4 105.6 15.7 17.0 679.3 Equity in earnings (losses) of equity method investees—net 3.6 2.4 5.8 — 0.4 (0.7 ) 11.5 Amortization of goodwill and others 1.1 0.1 0.2 0.4 3.8 0.5 6.1 Net business profits (losses) (4) (5.1 ) 131.9 106.8 185.5 4.5 (4.2 ) 419.4 Fixed assets (5) 518.5 186.3 157.0 90.9 0.1 768.5 1,721.3 Notes: (1) 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. (2) “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 non-consolidated (3) “General and administrative expenses” excludes non-allocated (4) 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 (5) “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; right-of-use (6) “Others” includes the following items: • profits and expenses pertaining to consolidated subsidiaries that are not subject to allocation; • consolidating adjustments, including elimination • equity in earnings (losses) of equity method investees-net • profits and losses pertaining to derivative transactions that reflect the counterparty risk of the individual parties and other factors in determining fair market value. Reconciliation As explained above, the measurement bases of the internal management reporting systems and the income and expenses items included are different from the accompanying consolidated statements of income. Therefore, it is impracticable to present reconciliations of all the business segment’s information, other than net business profits (losses), to the corresponding items in the accompanying consolidated statements of income. A reconciliation of “Net business profits (losses) + Net gains (losses) related to ETFs and others” for the six months ended September 30, 2019 and 2020 presented above to income before income tax expense shown on the consolidated statements of income and a reconciliation of “Fixed assets” at September 30, 2019 and 2020 to the total amount of Premises and equipment - right-of-use Six months ended September 30, 2019 (in billions of yen) Net business profits (losses) + Net gains (losses) related to ETFs and others 340.9 419.4 Adjustment to reconcile management reporting to Japanese GAAP: General and administrative expenses: non-allocated 24.5 4.1 Expenses related to portfolio problems (including reversal of (provision for) general reserve for losses on loans) (19.1 ) (84.8 ) Gains on reversal of reserves for possible losses on loans, and others 7.9 3.6 Net gains (losses) related to stocks—Net gains (losses) related to ETFs and others 55.4 (50.5 ) Net extraordinary gains (losses) (5.0 ) 65.8 Others (13.1 ) (24.2 ) Income before income tax expense under Japanese GAAP 391.5 333.4 Adjustment to reconcile Japanese GAAP to U.S. GAAP: Derivative financial instruments and hedging activities 105.0 (12.9 ) Investments (163.9 ) 285.4 Loans — (10.8 ) Allowances for credit losses (1) 0.5 35.8 Premises and equipment (51.5 ) (37.1 ) Land revaluation 0.5 2.7 Business combinations 4.1 (4.3 ) Pension liabilities (27.3 ) (84.5 ) Consolidation of variable interest entities 40.3 36.6 Foreign currency translation 14.3 (0.2 ) Others (3.0 ) 3.7 Income before income tax expense under U.S. GAAP 310.5 547.8 As of September 30, (in billions of yen) Fixed assets 1,701.6 1,721.3 U.S. GAAP adjustments (2) 964.5 818.4 Premises and equipment-net right-of-use 2,666.1 2,539.7 Notes: (1) The MHFG Group adopted ASU No.2016-13, 2019-04, 2019-05, 2019-11 off-balance-sheet (2) The U.S. GAAP adjustments are primarily comprised of GAAP differences mainly from right-of-use

Subsequent events

Subsequent events	6 Months Ended
	Sep. 30, 2020
Subsequent Events [Abstract]
Subsequent Events	21. Subsequent events Share consolidation of MHFG’s common stock On June 25, 2020, a 1-for-10 Transition from defined benefit pension plan to defined contribution pension plan MHFG and certain domestic subsidiaries changed their defined benefit pension plans including partial transition from the defined benefit pension plans to the defined contribution pension plans, effective as of October 1, 2020. 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. As a result of the settlement, the benefit obligations and the plan assets decreased by ¥22 billion and ¥24 billion, respectively.

Basis of presentation (Policies

Basis of presentation (Policies)	6 Months Ended
	Sep. 30, 2020
Basis of presentation	1. Basis of presentation Mizuho Financial Group, Inc. (“MHFG”) is a joint stock corporation with limited liability under the laws of Japan. MHFG is a holding company for Mizuho Bank, Ltd. (“MHBK”), Mizuho Trust & Banking Co., Ltd. (“MHTB”), Mizuho Securities Co., Ltd. (“MHSC”), Asset Management One Co., Ltd. (“Asset Management One”), and other subsidiaries. MHFG, through its subsidiaries (“the MHFG Group,” or “the Group”), provides domestic and international financial services in Japan and other countries. For a discussion of the Group’s segment information, see Note 20 “Business segment information.” MHFG and its domestic subsidiaries as well as its foreign subsidiaries maintain their accounting records in accordance with the accounting standards of Japan and those standards of the countries in which they are domiciled. Certain adjustments and reclassifications have been incorporated in the accompanying consolidated financial statements to conform them to the accounting principles generally accepted in the United States of America (“U.S. GAAP”). The consolidated financial statements are stated in Japanese yen, the currency of the country in which MHFG is incorporated and principally operates. The accompanying consolidated financial statements include the accounts of MHFG and its subsidiaries. MHFG’s interim financial reporting period ends on September 30. Certain of MHFG’s subsidiaries have different interim financial reporting periods than September 30. For those subsidiaries with interim financial reporting periods within three months of MHFG’s interim financial reporting period, the effect of intervening events that materially affect the financial position or results of operations through the date of each of the periods presented in the MHFG’s consolidated financial statements have been considered for adjustment and/or disclosure. When determining whether to consolidate investee entities, the MHFG Group performs an analysis of the facts and circumstances of the particular relationships between the MHFG Group and the investee entities as well as the ownership of voting shares. The consolidated financial statements also include the accounts of VIEs for which MHFG or its subsidiaries have been determined to be the primary beneficiary in accordance with the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) 810, “Consolidation” (“ASC 810”). All significant intercompany transactions and balances have been eliminated upon consolidation. The MHFG Group accounts for investments in entities over which it has significant influence by using the equity method of accounting. These investments are included in Other investments and the Group’s proportionate share of income or loss is included in Equity in earnings (losses) of equity method investees-net. On June 25, 2020, a 1-for-10 share consolidation was approved at the Ordinary General Meeting of Shareholders and it became effective on October 1, 2020. All share and per share information with respect to MHFG’s common stock and preferred stock have been restated to reflect the effect of the share consolidation and related amendments to the articles of incorporation for all periods presented. See Equity on the consolidated balance sheets, Earnings per common share and Dividends per share on the consolidated statements of income, Note 7 “Preferred and common stock,” and Note 10 “Earnings per common share” for the restated figures. In addition, certain other comparative amounts for the prior period have been reclassified in order to conform to the current period’s presentation. The unaudited consolidated financial statements should be read in conjunction with the audited financial statements and related notes thereto included in the annual financial statements for the fiscal year ended March 31, 2020. Certain financial information that is normally included in annual financial statements prepared in accordance with U.S. GAAP, but is not required for interim reporting purposes, has been condensed or omitted.
Use of estimates	Use of estimates The preparation of the consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect reported amounts and related disclosures. Specific areas, among others, requiring the application of management’s estimates and judgment include assumptions pertaining to the allowance for credit losses, valuation of deferred tax assets, valuation of derivative financial instruments, valuation of investments and valuation of pension and other employee benefits. During times of pandemics and dislocated markets, such as COVID-19,
Financial instruments—current expected credit losses ("CECL")	Financial instruments—current expected credit losses (“CECL”) The adoption of this guidance established a single allowance framework for all financial assets measured at amortized cost and certain off-balance-sheet instrument exposures. This framework requires management’s estimate to reflect credit losses over the instrument’s remaining expected lives and consider expected future changes in macroeconomic conditions. The following note and Note 2 “Issued accounting pronouncements,” Note 3 “Investments,” Note 4 “Loans” and Note 5 “Allowance for credit losses on loans” provide further information about the impact that the adoption of ASC 326, “Financial Instruments - Credit Losses” (“ASC 326”) had on the MHFG Group.
Allowance for credit losses on loans	Allowance for credit losses on loans Effective April 1, 2020, the allowance for credit losses on loans is established for current expected credit losses on the MHFG Group’s loan portfolio in accordance with ASC 326. Prior to April 1, 2020, the allowance for credit losses on loans was established based on an incurred loss model in accordance with ASC 310, “Receivables” (“ASC 310”) and ASC 450, “Contingencies” (“ASC 450”). The MHFG Group makes adjustments to the allowance for credit losses on loans through Provision (credit) for credit losses in the consolidated statements of income in each subsequent reporting period. Loan principal that management judges to be uncollectible, based on detailed loan reviews and a credit quality assessment, is charged off against the allowance for credit losses on loans. In general, the Group charges off loans when the Group determines that the obligor should be classified as substantially bankrupt or bankrupt. See Note 4 “Loans” for the definitions of obligor categories. Obligors in the retail portfolio segment are generally determined to be substantially bankrupt when they are past due for more than six months, and as for obligors in the corporate portfolio segment, the Group separately monitors the credit quality of each obligor without using time-based triggers. The Group does not record expected credit losses for accrued interest receivables because uncollectible accrued interest is reversed through interest income in a timely manner in line with the Group’s nonaccrual and past due policies for loans. The MHFG Group maintains an appropriate allowance for credit losses on loans to represent management’s estimate of the expected credit losses in the Group’s loan portfolio. The management evaluates the appropriateness of the allowance for credit losses on loans semi-annually. The allowance considers expected credit losses over the remaining expected lives of the applicable instruments. The expected life of each instrument is determined by considering expected prepayments, contractual terms and cancellation features. When determining expected credit losses, a single forward-looking macroeconomic scenario is considered over a reasonable and supportable forecast period. This forward-looking macroeconomic scenario is based on the Group’s stress testing and in line with the scenario used for the Group’s business plan. If the scenario does not reflect a sudden change in economic conditions adequately, it could be possible to make adjustments to the scenario. After the forecast period, the Group reverts to long-term historical loss experience with a certain graduated transition period, to estimate losses over the remaining lives. The macroeconomic scenario is updated at least semi-annually and is reviewed accordingly to reflect current economic conditions and the Group’s expectation of future conditions on a timely basis. For April 1, 2020 and September 30, 2020, the Group used the most recent macroeconomic scenario available during the Group’s credit loss estimation process. In terms of the internal risk ratings, for the corporate portfolio segment, the credit quality review process and the credit rating process serve as the basis for determining the allowance for credit losses on loans. Through such processes loans are categorized into groups to reflect the probability of default, whereby the MHFG Group’s management assesses the ability of borrowers to service their debt, taking into consideration current financial information, ability to generate cash, historical payment experience, analysis of relevant industry segments and current trends. For the retail portfolio segment, the different categories of past due status of loans are primarily utilized in the credit quality review and the credit rating processes as the basis for determining the allowance for credit losses on loans. In general, the MHFG Group estimates expected credit losses collectively on the loans in the case of normal and watch obligors, considering the risk associated with a particular pool and the probability that the exposures within the pool will deteriorate or default. The allowance for credit losses on nonaccrual loans includes the allowance for groups of loans which were collectively evaluated for expected credit losses, in addition to the allowance for those loans that were individually evaluated for expected credit losses. See The estimation of expected credit losses that are evaluated collectively begins with a quantitative calculation that considers the likelihood of the borrower changing delinquency status or moving from one obligor category or rating to another. The quantitative calculation covers expected credit losses over an instrument’s expected life and is estimated by applying credit loss factors to the MHFG Group’s estimated exposure at default. The credit loss factors incorporate the probability of default as well as the loss given default based on the historical loss rates and the external ratings such as S&P. The model and inputs used to determine credit losses on loans that are evaluated collectively are analyzed on a periodic basis by comparing the estimated values with the actual results subsequent to the balance sheet date. The MHFG Group divides its overall portfolio into domestic and foreign portfolios, and categorizes the domestic portfolio into four portfolio segments according to their risk profiles: corporate, retail, sovereign, and banks and financial institutions. The corporate portfolio segment consists of loans originated primarily by MHBK and MHTB, and includes mainly business loans such as those used for working capital and capital expenditure, as well as loans for which the primary source of repayment of the obligation is income generated by the relevant assets such as project finance, asset finance and real estate finance. The corporate portfolio segment is divided into two classes based on their risk characteristics: large companies, and small and medium-sized The retail portfolio segment consists mainly of residential mortgage loans originated by MHBK, and it is divided into two classes based on their risk characteristics: housing loan and others. For the retail portfolio segment, the Japanese unemployment rate is applied as a key factor. As it pertains to troubled debt restructuring (“TDR”) loans in the retail portfolio segment, which are subject to collective evaluation for expected credit losses, the restructuring itself, as well as subsequent payment defaults, if any, are considered in determining obligor categories. Expected credit loss estimates also include consideration of expected cash recoveries on loans previously charged-off, or expected recoveries on collateral dependent loans where recovery is expected through sale of the collateral. The allowance recorded for individually evaluated loans is based on (1) the present value of expected future cash flows, after considering the restructuring effect and subsequent payment default with respect to TDRs, discounted at the loan’s initial effective interest rate, or (2) the loan’s observable market price, or (3) the fair value of the collateral if the loan is collateral dependent. The collateral that the MHFG Group obtains for loans consists primarily of real estate. In obtaining the collateral, the Group evaluates the fair value of the collateral and its legal enforceability. The Group also performs subsequent re-evaluations at least once a year. As it pertains to real estate collateral, valuation is generally performed by an appraising subsidiary which is independent from the Group’s loan origination departments by using generally accepted valuation techniques such as (1) the replacement cost approach, (2) the sales comparison approach or (3) the income approach. In the case of large real estate collateral, the Group generally engages third-party appraisers to perform the valuation. The MHFG Group’s methodology for determining the appropriate allowance for credit losses on loans also considers the imprecision inherent in the methodologies used. As a result, the amounts determined under the methodologies described above could be adjusted by management to consider the potential impact of other qualitative factors which include, but are not limited to ,
Allowance for credit losses on available-for-sale securities	Allowance for credit losses on available-for-sale The MHFG Group performs periodic reviews to identify impaired securities in accordance with ASC 326. Available-for-sale securities are impaired if the fair value is less than the amortized cost (excluding accrued interest receivable). For available-for-sale available-for-sale available-for-sale is recognized immediately through earnings. In other cases, the Group evaluates expected cash flows to be received and determines if a credit loss exists, and if so, the amount of the credit loss is recognized in Provision (credit) for credit losses, while the remaining decline in fair value is recognized in other comprehensive income, net of applicable taxes. The Group generally does not record an allowance for credit losses for accrued interest receivables related to available-for-sale securities because these receivables are reversed through interest income, consistent with the Group’s past due policies. For additional information, see Note 4 “Loans.” Before the adoption of ASC 326, the previous other-than-temporary impairment model was applied for available-for-sale

Issued accounting pronounceme_2

Issued accounting pronouncements (Tables)	6 Months Ended
	Sep. 30, 2020
Accounting Standards Update and Change in Accounting Principle [Abstract]
Schedule of New Accounting Pronouncements and Changes in Accounting Principles	The following table reconciles the closing allowance for loans and off-balance-sheet the opening allowance determined with ASC 326 at April 1, 2020: At March 31, 2020 ASC 310/450 Transition Adjustment At April 1, 2020 ASC 326 (in billions of yen) Loans: Corporate 413 78 491 Retail 28 78 106 Off-balance-sheet 46 20 66

Investments (Tables)

Investments (Tables)	6 Months Ended
	Sep. 30, 2020
Amortized Cost, Gross Unrealized Gains and Losses, and Fair Value of Available-for-Sale and Held-to-Maturity Securities	The amortized cost, net of allowance for credit losses, gross unrealized gains and losses, and fair value of available-for-sale and held-to-maturity securities at March 31, 2020 and September 30, 2020 are as follows: Amortized (5)(6) Gross unrealized gains Gross unrealized losses Fair value (in millions of yen) March 31, 2020 Available-for-sale Debt securities: Japanese government bonds 12,651,677 1,319 50,224 12,602,772 Japanese local government bonds 272,412 649 494 272,567 U.S. Treasury bonds and federal agency securities 927,172 7,733 — 934,905 Other foreign government bonds 1,408,009 3,273 202 1,411,080 Agency mortgage-backed securities (1) 494,958 10,490 434 505,014 Residential mortgage-backed securities 83,077 1,405 151 84,331 Commercial mortgage-backed securities 609,559 5,551 106 615,004 Japanese corporate bonds and other debt securities (2) 1,836,540 7,489 8,772 1,835,257 Foreign corporate bonds and other debt securities (3) 849,595 2,595 168 852,022 Total 19,132,999 40,504 60,551 19,112,952 Held-to-maturity Debt securities: Japanese government bonds 479,936 13,357 — 493,293 Agency mortgage-backed securities (4) 382,095 1,245 1,303 382,037 Total 862,031 14,602 1,303 875,330 September 30, 2020 Available-for-sale Debt securities: Japanese government bonds 19,964,553 1,084 45,274 19,920,363 Japanese local government bonds 406,873 757 446 407,184 U.S. Treasury bonds and federal agency securities 625,398 1,388 2 626,784 Other foreign government bonds 1,353,376 3,020 74 1,356,322 Agency mortgage-backed securities (1) 509,808 10,650 433 520,025 Residential mortgage-backed securities 78,883 1,220 123 79,980 Commercial mortgage-backed securities 634,537 6,674 69 641,142 Japanese corporate bonds and other debt securities (2) 2,066,234 12,579 8,785 2,070,028 Foreign corporate bonds and other debt securities (3) 922,752 3,410 1,190 924,972 Total 26,562,414 40,782 56,396 26,546,800 Held-to-maturity Debt securities: Japanese government bonds 479,947 11,505 — 491,452 Agency mortgage-backed securities (4) 310,031 10,666 — 320,697 Total 789,978 22,171 — 812,149 Notes: (1) Agency mortgage-backed securities presented in this line consist of Japanese and Foreign agency mortgage-backed securities, of which the fair values were ¥504,953 million and ¥61 million, respectively, at March 31, 2020, and ¥ 519,974 51 (2) Other debt securities presented in this line primarily consist of Japanese asset-backed securities (“ABS”), of which the total fair values was million at September 30, 2020. (3) Other debt securities presented in this line primarily consist of Foreign negotiable certificates of deposit (“NCDs”) and ABS, of which the total fair values were ¥271,387 million at March 31, 2020, and ¥319,044 million at September 30, 2020. (4) All Agency mortgage-backed securities presented in this line are Ginnie Mae securities. (5) Amortized cost, net of the allowance for credit losses, of which the amounts related to available-for-sale (6) Accrued interest receivables are excluded from amortized cost, of which the amount was million at September 30, 2020 and included in Acc rued income.
Amortized Cost and Fair Value of Available-for-Sale and Held-to-Maturity Securities by Contractual Maturity	The amortized cost, net of allowance for credit losses, and fair value available-for-sale held-to-maturity Amortized cost Due in one year or less Due after one year through five years Due after five years through ten years Due after ten years Total (in millions of yen) Available-for-sale Debt securities: Japanese government bonds 14,588,119 3,630,141 1,550,745 195,548 19,964,553 Japanese local government bonds 30,537 209,317 149,994 17,025 406,873 U.S. Treasury bonds and federal agency securities 625,398 — — — 625,398 Other foreign government bonds 1,024,723 326,539 1,058 1,056 1,353,376 Agency mortgage-backed securities — — — 509,808 509,808 Residential mortgage-backed securities — — — 78,883 78,883 Commercial mortgage-backed securities 6,080 252,315 375,342 800 634,537 Japanese corporate bonds and other debt securities 94,088 820,338 587,344 564,464 2,066,234 Foreign corporate bonds and other debt securities 453,235 343,496 123,123 2,898 922,752 Total 16,822,180 5,582,146 2,787,606 1,370,482 26,562,414 Held-to-maturity Debt securities: Japanese government bonds — 479,947 — — 479,947 Agency mortgage-backed securities — — — 310,031 310,031 Total — 479,947 — 310,031 789,978 Fair value Due in one year or less Due after one year through five years Due after five years through ten years Due after ten years Total (in millions of yen) Available-for-sale Debt securities: Japanese government bonds 14,586,652 3,619,928 1,522,868 190,915 19,920,363 Japanese local government bonds 30,553 209,557 149,982 17,092 407,184 U.S. Treasury bonds and federal agency securities 626,784 — — — 626,784 Other foreign government bonds 1,025,928 328,280 1,058 1,056 1,356,322 Agency mortgage-backed securities — — — 520,025 520,025 Residential mortgage-backed securities — — — 79,980 79,980 Commercial mortgage-backed securities 6,085 254,025 380,219 813 641,142 Japanese corporate bonds and other debt securities 94,089 819,848 585,922 570,169 2,070,028 Foreign corporate bonds and other debt securities 454,356 344,474 123,244 2,898 924,972 Total 16,824,447 5,576,112 2,763,293 1,382,948 26,546,800 Held-to-maturity Debt securities: Japanese government bonds — 491,452 — — 491,452 Agency mortgage-backed securities — — — 320,697 320,697 Total — 491,452 — 320,697 812,149
Gross Unrealized Losses and Fair Value of Available-for-Sale and Held-to-Maturity Securities, Aggregated by Length of Time that Individual Securities Have Been in a Continuous Unrealized Loss Position	The following table shows the gross unrealized losses and fair value of available-for-sale held-to-maturity Less than 12 months 12 months or more Total Fair value Gross unrealized losses Fair value Gross unrealized losses Fair value Gross unrealized losses (in millions of yen) March 31, 2020 Available-for-sale Debt securities: Japanese government bonds 10,339,320 43,204 283,561 7,020 10,622,881 50,224 Japanese local government bonds 162,665 418 34,114 76 196,779 494 U.S. Treasury bonds and federal agency securities — — — — — — Other foreign government bonds 196,990 202 — — 196,990 202 Agency mortgage-backed securities (1) 30,913 227 9,504 207 40,417 434 Residential mortgage-backed securities 9,524 62 5,450 89 14,974 151 Commercial mortgage-backed securities 15,115 85 7,478 21 22,593 106 Japanese corporate bonds and other debt securities 669,572 5,507 608,361 3,265 1,277,933 8,772 Foreign corporate bonds and other debt securities 152,058 165 5,564 3 157,622 168 Total 11,576,157 49,870 954,032 10,681 12,530,189 60,551 Held-to-maturity Debt securities: Agency mortgage-backed securities (2) — — 191,244 1,303 191,244 1,303 Total — — 191,244 1,303 191,244 1,303 September 30, 2020 Available-for-sale Debt securities: Japanese government bonds 9,978,136 23,884 1,234,118 21,390 11,212,254 45,274 Japanese local government bonds 126,991 246 72,086 200 199,077 446 U.S. Treasury bonds and federal agency securities 29,093 2 — — 29,093 2 Other foreign government bonds 278,022 74 — — 278,022 74 Agency mortgage-backed securities (1) 30,948 202 9,799 231 40,747 433 Residential mortgage-backed securities 9,567 41 6,794 82 16,361 123 Commercial mortgage-backed securities 6,052 15 11,396 54 17,448 69 Japanese corporate bonds and other debt securities 565,278 3,028 597,714 5,757 1,162,992 8,785 Foreign corporate bonds and other debt securities 245,311 1,187 2,712 3 248,023 1,190 Total 11,269,398 28,679 1,934,619 27,717 13,204,017 56,396 Held-to-maturity Debt securities: Agency mortgage-backed securities (2) — — — — — — Total — — — — — — Notes: (1) Agency mortgage-backed securities presented in this line consist of Japanese agency mortgage-backed securities, of which the fair values were ¥40,417 million at March 31, 2020, and ¥40,747 million at September 30, 2020. All Japanese agency mortgage-backed securities are issued by Japan Housing Finance Agency, a Japanese government-sponsored enterprise. (2) All Agency mortgage-backed securities presented in this line are Ginnie Mae securities.
Realized Gains and Losses on Sales of Available-for-Sale Securities	The following table shows the realized gains and losses on sales of available-for-sale Six months ended September 30, 2019 2020 (in millions of yen) Gross realized gains 36,183 5,101 Gross realized losses (6,167 ) (3,694 ) Net realized gains (losses) on sales of available-for-sale 30,016 1,407
Summary of Details of Net Gains and Losses on Equity Securities	The following table shows the details of the net gains and losses on Equity securities for the six months ended September 30, 2019 and 2020: Six months ended September 30, 2019 2020 (in millions of yen) Net gains (losses) recognized during the period on equity securities (126,648 ) 266,119 Less: Net gains (losses) recognized during the period on equity securities sold during the period (3,084 ) 34,985 Unrealized gains (losses) recognized during the reporting period on equity securities still held at the (123,564 ) 231,134
Summary of Equity Securities Without Readily Determinable Fair Values	The following table shows carrying amounts of equity securities without readily determinable fair values, for which the measurement alternative is used, and cumulative amounts due to downward adjustments and impairments and upward adjustments, at March 31, 2020 and September 30, 2020: March 31, 2020 September 30, 2020 (in millions of yen) Carrying amounts at the end of the period 419,775 402,194 Downward adjustments and impairments 2,435 3,800 Upward adjustments 9,128 9,104 The following table shows amounts recognized in earnings during the period due to downward adjustments and impairments and upward adjustments for equity securities without readily determinable fair values. Six months ended September 30, 2019 2020 (in millions of yen) Downward adjustments and impairments 430 1,411 Upward adjustments 6,527 34
Summary of Composition of Other Investments	The following table summarizes the composition of Other investments at March 31, 2020 and September 30, 2020: March 31, 2020 September 30, 2020 (in millions of yen) Equity method investments 404,513 412,281 Investments held by consolidated investment companies 39,438 55,682 Total 443,951 467,963

Loans (Tables)

Loans (Tables)	6 Months Ended
	Sep. 30, 2020
Loans Outstanding by Domicile and Industry of Borrower	The table below presents loans outstanding by domicile and industry of borrower at March 31, 2020 and September 30, 2020: March 31, 2020 September 30, 2020 (in millions of yen) Domestic: Manufacturing 9,731,028 11,700,375 Construction and real estate 9,603,433 10,172,843 Services 5,992,511 6,294,310 Wholesale and retail 5,219,727 5,415,605 Transportation and communications 3,832,884 3,978,708 Banks and other financial institutions 4,634,442 4,719,863 Government and public institutions 2,198,805 2,639,956 Other industries (Note) 5,389,347 5,517,220 Individuals: Mortgage loans 8,567,099 8,357,042 Other 861,235 798,475 Total domestic 56,030,511 59,594,397 Foreign: Commercial and industrial 20,818,709 20,190,048 Banks and other financial institutions 10,475,277 10,502,326 Government and public institutions 317,284 308,171 Other 35,388 37,572 Total foreign 31,646,658 31,038,117 Total 87,677,169 90,632,514 Less: Unearned income and deferred loan fees—net 149,081 156,767 Total loans before allowance for credit losses on loans 87,528,088 90,475,747 Note: Other industries of domestic includes trade receivables and lease receivables of consolidated VIEs.
Credit Quality Information of Loans Based on MHFG Group's Internal Rating System	The table below presents credit quality information of loans based on the MHFG Group’s internal rating system at March 31, 2020 and September 30, 2020: September 30, 2020 March 31, 2020 Term loans by origination year Revolving Total Total 2020 2019 2018 2017 2016 Prior to 2016 (in millions of yen) Domestic: Corporate: Large companies: Normal obligors 9,754,935 7,343,964 7,517,546 2,710,108 2,498,507 2,978,989 8,279,869 41,083,918 37,979,353 Watch obligors excluding special attention obligors 424,745 92,446 82,206 56,363 33,737 33,847 196,544 919,888 840,289 Nonaccrual loans 142,730 55,771 41,249 20,295 11,956 29,551 136,213 437,765 343,439 Small and medium-sized Normal obligors 381,487 543,822 456,363 260,146 232,638 485,430 502,124 2,862,010 2,941,599 Watch obligors excluding special attention obligors 46,537 32,174 37,116 13,321 15,523 28,933 30,521 204,125 189,075 Nonaccrual 58,754 15,624 4,294 5,900 2,636 9,849 28,118 125,175 119,759 Retail: Housing Loan: Normal obligors 437,780 668,358 627,669 634,528 783,929 4,879,204 — 8,031,468 8,215,781 Watch obligors excluding special attention obligors 560 1,178 1,827 1,579 2,217 43,397 — 50,758 57,478 Nonaccrual 18,941 6,528 1,525 1,432 1,778 38,456 — 68,660 57,696 Others: Normal obligors 327,506 209,899 152,679 106,359 102,735 361,209 523,640 1,784,027 1,783,779 Watch obligors excluding special attention obligors 36,270 17,587 11,754 6,911 4,534 6,846 12,185 96,087 81,463 Nonaccrual 26,633 6,905 1,945 1,000 965 9,532 11,567 58,547 59,782 Sovereign Normal obligors 1,907,424 264,528 126,868 87,021 92,664 485,721 13,700 2,977,926 2,559,420 Watch obligors excluding special attention obligors 2,859 6,914 2,951 1,134 257 34 — 14,149 10,939 Nonaccrual — — — — — — — — — Banks and other financial institutions Normal obligors 15,637 155,415 261,601 26,841 85,303 74,009 187,102 805,908 790,659 Watch obligors excluding special attention obligors — — — — — — — — — Nonaccrual 167 — 180 — — — 1,600 1,947 — Total domestic 13,582,965 9,421,113 9,327,773 3,932,938 3,869,379 9,465,007 9,923,183 59,522,358 56,030,511 Foreign: Corporate: Normal obligors 10,181,936 5,813,342 3,419,918 1,298,791 804,580 1,624,422 4,630,806 27,773,795 28,555,991 Watch obligors excluding special attention obligors 172,225 43,785 47,998 37,862 15,899 35,532 84,646 437,947 336,470 Nonaccrual 41,085 25,405 12,954 5,422 8,448 21,241 43,592 158,147 135,522 Retail: Normal obligors 3,613 9,806 6,008 2,956 1,517 2,527 102 26,529 30,862 Watch obligors excluding special attention obligors 174 1,110 647 361 109 11 — 2,412 858 Nonaccrual 26 506 287 103 44 1 — 967 6 Sovereign Normal obligors 91,542 99,248 32,403 149,794 5,907 90,988 81,008 550,890 558,384 Watch obligors excluding special attention obligors — — — — — 20,124 — 20,124 19,971 Nonaccrual — 741 — — — — — 741 — Banks and other financial institutions Normal obligors 750,039 654,755 421,876 95,375 4,509 3,536 49,997 1,980,087 2,008,516 Watch obligors excluding special attention obligors 912 152 686 — — — — 1,750 78 Nonaccrual — — — — — — — — — Total foreign 11,241,552 6,648,850 3,942,777 1,590,664 841,013 1,798,382 4,890,151 30,953,389 31,646,658 Total 24,824,517 16,069,963 13,270,550 5,523,602 4,710,392 11,263,389 14,813,334 90,475,747 87,677,169 Notes: (1) Special attention obligors are watch obligors with debt in TDR or 90 days or more delinquent debt. Loans to such obligors are considered nonaccrual. (2) The primary component of the retail portfolio segment is housing loans to individuals which obligor category is classified based on past due status. The trigger to reclassify obligors from normal obligors to watch obligors excluding special attention obligors is when the past due status is more than 30 days. (3) There were no significant revolving line of credit arrangements that converted to term loans during the six months ended September 30, 2020.
Impaired Loans Information	The table below presents nonaccrual loans information at March 31, 2020 and September 30, 2020: Amortized cost Nonaccrual loans with an allowance Nonaccrual loans without an allowance Total nonaccrual loans Interest income recognized (in millions of yen) March 31, 2020 Domestic: Corporate: Large companies 333,442 9,997 343,439 4,155 Small and medium-sized 102,786 16,973 119,759 1,724 Retail: Housing Loan 28,263 29,433 57,696 937 Others 36,220 23,562 59,782 846 Total domestic 500,711 79,965 580,676 7,662 Foreign: Total foreign 95,289 40,239 135,528 3,032 Total 596,000 120,204 716,204 10,694 September 30, 2020 Domestic: Corporate: Large companies 416,637 21,128 437,765 2,501 Small and medium-sized 105,556 19,619 125,175 777 Retail: Housing Loan 40,358 28,302 68,660 535 Others 36,270 22,277 58,547 373 Banks and other financial institutions 1,947 — 1,947 3 Total domestic 600,768 91,326 692,094 4,189 Foreign: Total foreign 110,295 49,560 159,855 958 Total 711,063 140,886 851,949 5,147 Notes: (1) Amounts represent the outstanding bal a (2) Amounts represent the amount of interest income on nonaccrual loans recognized on a cash basis and included in Interest income on loans in the consolidated statements of income. (3) The majority of total foreign consist of corporate.
Troubled Debt Restructurings Entered Modified Periods by Type of Concession Granted	The following table presents modified loans that were determined to be TDRs during the six months ended September 30, 2019 and 2020: Loan forgiveness or debt to equity swaps Interest rate reduction and/or postponement of principal and/or Recorded investment (1) Charge-offs (in millions of yen) September 30, 2019 Domestic: Corporate: Large companies 689 3,806 152,373 Small and medium-sized — — 55,344 Retail: Housing Loan — — 3,742 Others — — 7,468 Total domestic 689 3,806 218,927 Foreign: Total foreign 470 4,922 38,646 Total 1,159 8,728 257,573 September 30, 2020 Domestic: Corporate: Large companies — — 264,952 Small and medium-sized — — 54,760 Retail: Housing Loan — — 14,690 Others — — 9,130 Banks and other financial institutions — — 1,600 Total domestic — — 345,132 Foreign: Total foreign — — 80,889 Total — — 426,021 Notes: (1) Amounts represent the b o (2) The majority of total foreign consist of corporate
Payment Defaults Occurred During Periods with Respect to Loans Modified as Troubled Debt Restructurings within Previous Twelve Months	The following table presents payment defaults which occurred during the six months ended September 30, 2019 and 2020 with respect to the loans modified as TDRs within the previous twelve months: Recorded investment September 30, 2019 September 30, 2020 (in millions of yen) Domestic: Corporate: Large companies 5,875 2,084 Small and medium-sized 2,444 3,861 Retail: Housing Loan 686 505 Others 1,349 1,104 Total domestic 10,354 7,554 Foreign: Total foreign 6,436 43,786 Total 16,790 51,340
Age Analysis of Past Due Loans	The table below presents an analysis of the age of the amortized cost basis in loans that are past due at March 31, 2020 and September 30, 2020: 30-59 days past due 60-89 days past due 90 days or more past due Total past due Current Total (in millions of yen) March 31, 2020 Domestic: Corporate: Large companies 2,146 2,013 38,364 42,523 39,120,558 39,163,081 Small and medium-sized 2,347 894 9,187 12,428 3,238,005 3,250,433 Retail: Housing Loan 15,703 10,078 26,690 52,471 8,278,484 8,330,955 Others 6,179 2,013 15,239 23,431 1,901,593 1,925,024 Sovereign — — — — 2,570,359 2,570,359 Banks and other financial institutions — — — — 790,659 790,659 Total domestic 26,375 14,998 89,480 130,853 55,899,658 56,030,511 Foreign: Total foreign 1,214 181 28,722 30,117 31,616,541 31,646,658 Total 27,589 15,179 118,202 160,970 87,516,199 87,677,169 September 30, 2020 Domestic: Corporate: Large companies 311 269 38,868 39,448 42,402,123 42,441,571 Small and medium-sized 2,093 604 11,226 13,923 3,177,387 3,191,310 Retail: Housing Loan 15,831 7,870 25,922 49,623 8,101,263 8,150,886 Others 4,720 1,436 14,152 20,308 1,918,353 1,938,661 Sovereign — — — — 2,992,075 2,992,075 Banks and other financial institutions — — — — 807,855 807,855 Total domestic 22,955 10,179 90,168 123,302 59,399,056 59,522,358 Foreign: Total foreign 1,826 636 60,535 62,997 30,890,392 30,953,389 Total 24,781 10,815 150,703 186,299 90,289,448 90,475,747 Note: The majority of total foreign consist of corporate .

Allowance for credit losses o_2

Allowance for credit losses on loans (Tables)	6 Months Ended
	Sep. 30, 2020
Changes in Allowance for Loan Losses, Allowance for Loan Losses and Loans Outstanding Disaggregated on Basis of Impairment Method, by Portfolio Segment	Changes in Allowance for credit losses on loans by portfolio segment for the six months ended September 30, 2019 and 2020 are shown below: Corporate Retail Total (in millions of yen) Six months ended September 30, 2019 Balance at beginning of period 277,955 29,246 307,201 Provision (credit) for credit losses on loans 12,268 1,505 13,773 Charge-offs (25,147 ) (3,887 ) (29,034 ) Recoveries 2,785 1,269 4,054 Net charge-offs (22,362 ) (2,618 ) (24,980 ) Others (Note) (4,570 ) (2 ) (4,572 ) Balance at end of period 263,291 28,131 291,422 Six months ended September 30, 2020 Balance at beginning of period 413,026 27,829 440,855 April 1, 2020 adoption of CECL 77,514 78,241 155,755 Adjusted Balance at beginning of period 490,540 106,070 596,610 Provision (credit) for credit losses on loans 64,133 (11,051 ) 53,082 Charge-offs (28,417 ) (3,446 ) (31,863 ) Recoveries 5,260 479 5,739 Net charge-offs (23,157 ) (2,967 ) (26,124 ) Others (Note) (997 ) (45 ) (1,042 ) Balance at end of period 530,519 92,007 622,526 Note: Others includes primarily foreign exchange translation.

Other assets and liabilities (T

Other assets and liabilities (Tables)	6 Months Ended
	Sep. 30, 2020
Details of Other Assets and Liabilities	The following table sets forth the details of other assets and liabilities at March 31, 2020 and September 30, 2020: March 31, 2020 September 30, 2020 (in millions of yen) Other assets: Accounts receivable: Receivables from brokers, dealers and customers for securities transactions 783,439 898,924 Other 358,702 416,064 Collateral pledged: Collateral pledged for derivative transactions 1,246,026 1,079,050 Margins provided for futures contracts 602,039 316,791 Other 941,167 909,155 Prepaid pension cost 711,981 986,767 Right-of-use 613,068 586,365 Security deposits 107,294 108,204 Loans held for sale 60,084 22,404 Other 542,079 540,514 Total 5,965,879 5,864,238 Other liabilities: Accounts payable: Payables to brokers, dealers and customers for securities transactions 2,161,075 2,065,408 Other 375,127 365,446 Guaranteed trust principal ( Note 824,431 808,172 Lease liabilities 627,250 600,087 Collateral accepted: Collateral accepted for derivative transactions 846,426 587,426 Margins accepted for futures contracts 797,317 558,138 Unearned income 122,072 120,352 Other 1,244,697 1,194,591 Total 6,998,395 6,299,620 Note: Guaranteed trust principal, included in All other liabilities in the disclosure about consolidated VIEs in the accompanying balance sheets, is a liability of certain consolidated trust arrangements that meet the definition of a VIE for which the MHFG Group provides guarantees for the repayment of principal. See Note 15 “Variable interest entities and securitizations” for further discussion of the guaranteed principal money trusts.

Preferred and common stock (Tab

Preferred and common stock (Tables)	6 Months Ended
	Sep. 30, 2020
Preferred stock
Schedule of Stock by Class	The composition of preferred stock at March 31, 2020 and September 30, 2020 is as follows: Class of stock March 31, 2020 September 30, 2020 Authorized Issued Authorized Issued (number of shares) Class XIV preferred stock 90,000,000 — 90,000,000 — Class XV preferred stock 90,000,000 — 90,000,000 — Class XVI preferred stock 150,000,000 — 150,000,000 —

Accumulated other comprehensi_2

Accumulated other comprehensive income (loss), net of tax (Tables)	6 Months Ended
	Sep. 30, 2020
Changes in Each Component of AOCI	Changes in each component of Accumulated other comprehensive income (loss), net of tax (“AOCI”) for the six months ended September 30, 2019 and 2020 are as follows: Six months ended September 30, 2019 2020 (in millions of yen) AOCI, balance at beginning of period, previously reported 164,021 (9,494 ) Cumulative effect of change in accounting principles (Note) (1,052 ) — AOCI, balance at beginning of period, adjusted 162,969 (9,494 ) Net unrealized gains (losses) on available-for-sale Balance at beginning of period 22,019 (19,592 ) Unrealized holding gains (losses) during period 25,843 644 Less: reclassification adjustments for losses (gains) included in net income (20,824 ) 754 Change during period 5,019 1,398 Balance at end of period 27,038 (18,194 ) Foreign currency translation adjustments: Balance at beginning of period, previously reported (58,558 ) (109,872 ) Cumulative effect of change in accounting principles (Note) (1,052 ) — Balance at beginning of period, adjusted (59,610 ) (109,872 ) Foreign currency translation adjustments during period (63,466 ) (36,652 ) Less: reclassification adjustments for losses (gains) included in net income — (409 ) Change during period (63,466 ) (37,061 ) Balance at end of period (123,076 ) (146,933 ) Pension liability adjustments: Balance at beginning of period 196,446 69,455 Unrealized gains (losses) during period (1,720 ) 190,394 Less: reclassification adjustments for losses (gains) included in net income (2,130 ) 672 Change during period (3,850 ) 191,066 Balance at end of period 192,596 260,521 Own credit risk adjustments: Balance at beginning of period 4,114 50,515 Unrealized gains (losses) during period 7,320 (9,340 ) Less: reclassification adjustments for losses (gains) included in net income (1,277 ) (2,732 ) Change during period 6,043 (12,072 ) Balance at end of period 10,157 38,443 Total other comprehensive income (loss), net of tax attributable to MHFG shareholders (56,254 ) 143,331 AOCI, balance at end of period 106,715 133,837 Note: The MHFG Group adopted ASU No.2017-12, No.2017-12”) No.2017-12
Amounts Reclassified Out of Accumulated Other Comprehensive Income into Net Income	The following table shows the amounts reclassified out of AOCI into net income during the six months ended September 30, 2020: Six months ended September 30, 2020 Before tax (1) Tax effect (2) Net of tax before allocation to noncontrolling interests Net of tax attributable to noncontrolling interests (2) Net of tax attributable to MHFG shareholders (in millions of yen) Amounts reclassified out of AOCI into net income: Affected line items in the Net unrealized gains (losses) on available-for-sale (1,065 ) 306 (759 ) 5 (754 ) Investment gains (losses)-net Provision (credit) for credit Foreign currency translation adjustments 409 — 409 — 409 Foreign exchange gains (losses)-net Pension liability adjustments (1,004 ) 321 (683 ) 11 (672 ) Salaries and employee benefits Own credit risk adjustments 4,111 (1,259 ) 2,852 (120 ) 2,732 Other noninterest income (expenses) Total 2,451 (632 ) 1,819 (104 ) 1,715 Notes: (1) The financial statement li n e (2) 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.

Regulatory matters (Tables)

Regulatory matters (Tables)	6 Months Ended
	Sep. 30, 2020
Capital Adequacy Ratios of MHFG, MHBK, and MHTB Calculated in Accordance with Japanese GAAP and Guidelines Established by Financial Services Agency	Capital adequacy ratios and leverage ratios of MHFG, MHBK, and MHTB as of March 31, 2020 and September 30, 2020 calculated in accordance with Japanese GAAP and the guidelines established by the Financial Services Agency are set forth in the following table: March 31, 2020 September 30, 2020 Amount Ratio Amount Ratio (in billions of yen, except percentages) Consolidated: MHFG: Common Equity Tier 1 capital: Required (1) 4,978 8.01 5,159 8.01 Actual 7,245 11.65 7,453 11.57 Tier 1 capital: Required (1) 5,910 9.51 6,125 9.51 Actual 9,024 14.52 9,468 14.69 Total risk-based capital: Required (1) 7,152 11.51 7,413 11.51 Actual 10,722 17.25 11,133 17.28 Leverage Ratio: Required 6,629 3.00 5,874 (2) 3.00 Actual 9,024 4.08 9,468 (2) 4.83 MHBK: Common Equity Tier 1 capital: Required 2,567 4.50 2,689 4.50 Actual 6,501 11.39 6,756 11.30 Tier 1 capital: Required 3,422 6.00 3,585 6.00 Actual 8,275 14.50 8,765 14.66 Total risk-based capital: Required 4,563 8.00 4,780 8.00 Actual 9,865 17.29 10,338 17.30 Leverage Ratio: Required 6,160 3.00 5,450 (2) 3.00 Actual 8,275 4.02 8,765 (2) 4.82 MHTB: Common Equity Tier 1 capital: Required 93 4.50 87 4.50 Actual 489 23.64 509 26.24 Tier 1 capital: Required 124 6.00 116 6.00 Actual 489 23.66 509 26.24 Total risk-based capital: Required 165 8.00 155 8.00 Actual 491 23.74 510 26.27 Leverage Ratio: Required 216 3.00 156 (2) 3.00 Actual 489 6.79 509 (2) 9.79 March 31, 2020 September 30, 2020 Amount Ratio Amount Ratio (in billions of yen, except percentages) Non-consolidated: MHBK: Common Equity Tier 1 capital: Required 2,403 4.50 2,525 4.50 Actual 6,130 11.47 6,369 11.34 Tier 1 capital: Required 3,204 6.00 3,367 6.00 Actual 7,905 14.80 8,381 14.93 Total risk-based capital: Required 4,272 8.00 4,489 8.00 Actual 9,482 17.75 9,943 17.71 Leverage Ratio: Required 5,884 3.00 5,178 (2) 3.00 Actual 7,905 4.03 8,381 (2) 4.85 MHTB: Common Equity Tier 1 capital: Required 93 4.50 87 4.50 Actual 475 23.10 494 25.49 Tier 1 capital: Required 123 6.00 116 6.00 Actual 475 23.10 494 25.49 Total risk-based capital: Required 165 8.00 155 8.00 Actual 477 23.18 494 25.52 Leverage Ratio: Required 214 3.00 153 (2) 3.00 Actual 475 6.66 494 (2) 9.66 Notes: (1) The required ratios disclosed above, at March 31, 2020 and September 30, 2020, include the capital conservation buffer of 2.5%, the countercyclical capital buffer of 0.01%, and the additional loss absorbency requirements for global systemically important banks (“G-SIBs”) (“D-SIBs”) (2) The required and actual amounts disclosed above at September 30, 2020 exclude amounts of deposits to the Bank of Japan.

Earnings per common share (Tabl

Earnings per common share (Tables)	6 Months Ended
	Sep. 30, 2020
Computation of Basic and Diluted Earnings Per Common Share	The following table sets forth the computation of basic and diluted earnings per common share for the six months ended September 30, 2019 and 2020: Six months ended September 30, 2019 2020 (in millions of yen) Net income: Net income attributable to MHFG common shareholders 212,984 315,886 Effect of dilutive securities — — Net income attributable to common shareholders after assumed conversions 212,984 315,886 Six months ended September 30, 2019 2020 (thousands of shares) Shares: Weighted average common shares outstanding 2,536,800 2,537,272 Effect of dilutive securities: Stock options and the common shares of MHFG under the stock compensation programs (Note) 209 93 Weighted average common shares after assumed conversions 2,537,009 2,537,365 Six months ended September 30, 2019 2020 (in yen) Earnings per common share: Basic net income per common share 83.96 124.50 Diluted net income per common share (Note) 83.95 124.49 Note: For the six months ended September 30, 2020, 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.

Income taxes (Tables)

Income taxes (Tables)	6 Months Ended
	Sep. 30, 2020
Components of Income Tax Expense	The following table presents the components of Income tax expense for the six months ended September 30, 2019 and 2020: Six months ended 2019 2020 (in millions of yen) Current tax expense 88,437 79,954 Deferred tax expense (benefit) (5,317 ) 57,807 Total income tax expense 83,120 137,761
Detailed Amounts of Tax Effects of Items Recorded Directly in Equity	The preceding table does not reflect the tax effects of items recorded directly in Equity for the six months ended September 30, 2019 and 2020. The detailed amounts recorded directly in Equity are as follows: Six months ended 2019 2020 (in millions of yen) Net unrealized gains (losses) on available-for-sale Unrealized gains (losses) 11,023 579 Less: reclassification adjustments (9,192 ) 306 Total 1,831 885 Pension liability adjustments: Unrealized gains (losses) (643 ) 83,994 Less: reclassification adjustments (937 ) 321 Total (1,580 ) 84,315 Own credit risk adjustments: Unrealized gains (losses) (43 ) (2,351 ) Less: reclassification adjustments (588 ) (1,259 ) Total (631 ) (3,610 ) Total tax effect before allocation to noncontrolling interests (380 ) 81,590

Pension and other employee be_2

Pension and other employee benefit plans (Tables)	6 Months Ended
	Sep. 30, 2020
Components of Net Periodic Benefit Cost of Severance Indemnities and Pension Plans	The following table summarizes the components of net periodic benefit cost of the severance indemnities and pension plans of the MHFG Group for the six months ended September 30, 2019 and 2020: Six months ended 2019 2020 (in millions of yen) Service cost-benefits earned during the period 22,729 22,695 Interest costs on projected benefit obligations 2,666 2,931 Expected return on plan assets (20,158 ) (20,073 ) Amortization of prior service cost (benefits) 19 205 Amortization of net actuarial loss (gain) (3,064 ) 836 Special termination benefits 2,188 4,981 Net periodic benefit cost 4,380 11,575

Derivative financial instrume_2

Derivative financial instruments (Tables)	6 Months Ended
	Sep. 30, 2020
Summary of Notional and Fair Value Amounts of Derivative Instruments Outstanding	The following table summarizes the notional and fair value amounts of derivative instruments outstanding as of March 31, 2020 and September 30, 2020. The fair values of derivatives are presented on a gross basis, derivative receivables and payables are not offset. In addition, they are not offset against the amounts recognized for the right to reclaim cash collateral or the obligation to return cash collateral under master netting agreements in the consolidated balance sheets, or the table below. Fair value Derivative receivables (2) Derivative payables (2) March 31, 2020 Notional amount (1) Designated as hedges Not designated as hedges Designated as hedges Not designated as hedges (in billions of yen) Interest rate contracts 1,123,546 — 7,232 — 6,788 Foreign exchange contracts 185,359 — 2,926 — 2,899 Equity-related contracts 6,684 — 310 — 266 Credit-related contracts 4,676 — 30 — 29 Other contracts 400 — 38 — 39 Total 1,320,665 — 10,536 — 10,021 Fair value Derivative receivables (2) Derivative payables (2) September 30, 2020 Notional amount (1) Designated as hedges Not designated as hedges Designated as hedges Not designated as hedges (in billions of yen) Interest rate contracts 1,084,971 — 6,135 — 5,728 Foreign exchange contracts 174,856 — 2,143 — 2,160 Equity-related contracts 7,012 — 397 — 260 Credit-related contracts 7,742 — 55 — 77 Other contracts 397 — 28 — 26 Total 1,274,978 — 8,758 — 8,251 Notes: (1) Notional amount includes the sum of gross long and gross short third-party contracts. (2) Derivative receivables and payables are recorded in Trading account assets and Trading account liabilities, respectively.
Summary of Notional and Fair Value Amounts of Credit Derivatives	The following table summarizes the notional and fair value amounts of credit derivatives at March 31, 2020 and September 30, 2020: March 31, 2020 September 30, 2020 Notional amount Fair value Notional amount Fair value (in billions of yen) Credit protection written: Investment grade 1,400 (5 ) 2,687 37 Non-investment 416 — 530 8 Total 1,816 (5 ) 3,217 45 Credit protection purchased 3,028 6 4,693 (67 ) Note: The rating scale is based upon either the external ratings or the internal ratings of the underlying reference credit. The lowest investment grade rating is considered to be BBB - non-investment Non-investment
Maximum Potential Amount of Future Payments for Credit Protection Written by Expiration Period	The following table shows the maximum potential amount of future payments for credit protection written by expiration period at March 31, 2020 and September 30, 2020: Maximum payout/Notional amount March 31, 2020 September 30, 2020 (in billions of yen) One year or less 270 233 After one year through five years 1,368 2,793 After five years 178 191 Total 1,816 3,217 Note: The maximum potential amount of future payments is the aggregate notional amount of the credit derivatives where the Group wrote the credit protection, and it has not been reduced by the effect of any amounts that the Group may possibly collect on the underlying assets and the related cash flows, nor netted against that of credit protection purchased.
Quantitative Information about Derivative Instruments with Credit-risk-related Contingent Features	The following table shows the quantitative information about derivative instruments with credit-risk-related contingent features at March 31, 2020 and September 30, 2020: March 31, September 30, (in billions of yen) Aggregate fair value of derivative instruments with credit-risk-related contingent features in net liability positions 888 747 Collateral provided to counterparties in the normal course of business 818 703 Amount required to be posted as collateral or settled immediately if credit-risk-related contingent features were triggered 70 44
Not Designated as Hedging Instrument
Schedule of Derivative Instruments, Gain (Loss) in Statement of Financial Performance	The following table summarizes gains and losses on derivatives not designated or qualifying as hedges during the six months ended September 30, 2019 and 2020: Gains (losses) recorded in income for six months ended September 30, 2019 2020 (in millions of yen) Interest rate contracts 210,909 32,791 Foreign exchange contracts (30,736 ) 26,277 Equity-related contracts (1) (494 ) (31,999 ) Credit-related contracts (2) (3,546 ) (29,219 ) Other contracts (1,650 ) 26,692 Total 174,483 24,542 Notes: (1) The net gains (losses) excluded from the assessment of the effectiveness of fair value hedges is not included (2) Amounts include the net gains (losses) of ¥(426) million and ¥(1,221) million on the credit derivatives economically managing the credit risk of loans during the six months ended September 30, 2019 and 2020, respectively.
Net Investment Hedging | Designated as Hedging Instrument
Schedule of Derivative Instruments, Gain (Loss) in Statement of Financial Performance	The following table summarizes gains and losses information related to net investment hedges for the six months ended September 30, 2019 and 2020: Gains (losses) recorded in other for six months ended September 30, 2019 2020 (in millions of yen) Financial instruments hedging foreign exchange risk (1,044 ) 1,538 Total (1,044 ) 1,538 Note: Related to the net investment hedges, gains (losses) of ¥(260) million and ¥(1,312) million were reclassified

Commitments and contingencies (

Commitments and contingencies (Tables)	6 Months Ended
	Sep. 30, 2020
Summary of Maximum Potential Amount of Future Payments under Guarantees	the MHFG Group is exposed to unlimited losses; therefore, the table shows the notional amounts of the contracts as a substitute for the maximum exposure. March 31, 2020 September 30, 2020 (in billions of yen) Performance guarantees 2,456 2,527 Guarantees on loans 301 266 Guarantees on securities 110 96 Other guarantees 2,314 2,306 Guarantees for the repayment of trust principal 59 31 Liabilities of trust accounts 446 456 Derivative financial instruments 21,756 21,097
Summary of Contractual Amounts with Regard to Undrawn Commitments	The table below summarizes the contractual amounts with regard to these undrawn commitments at March 31, 2020 and September 30, 2020: March 31, 2020 September 30, 2020 (in billions of yen) Commitments to extend credit (Note) 76,633 86,359 Commercial letters of credit 690 537 Total 77,323 86,896 Note: Commitments to extend credit include commitments to invest in securities.
Performance guarantees, Guarantees on loans, Guarantees on securities and Other guarantees
Summary of Maximum Potential Amount of Future Payments under Guarantees	The table below presents the maximum potential amount of future payments of performance guarantees, guarantees on loans, guarantees on securities and other guarantees classified based on internal ratings at March 31, 2020 and September 30, 2020: March 31, 2020 September 30, 2020 (in billions of yen) Investment grade 4,233 4,079 Non-investment 948 1,116 Total 5,181 5,195 Note: Investment grade in the internal rating scale generally corresponds to BBB-

Variable interest entities an_2

Variable interest entities and securitizations (Tables)	6 Months Ended
	Sep. 30, 2020
Schedule of Variable Interest Entities	The table below shows the consolidated assets of the Group’s consolidated VIEs as well as total assets and maximum exposure to loss for its significant unconsolidated VIEs, in which the Group has determined that its maximum exposure to loss is greater than specific thresholds or meets certain other criteria as of March 31, 2020 and September 30, 2020: Consolidated VIEs Significant unconsolidated VIEs March 31, 2020 Consolidated assets Total assets Maximum exposure to (in billions of yen) Asset-backed commercial paper/loan programs 2,160 — — Asset-backed securitizations 572 77 7 Investments in securitization products 370 — — Investment funds 2,694 2,299 514 Trust arrangements and other 19 — — Total 5,815 2,376 521 Consolidated VIEs Significant unconsolidated VIEs September 30, 2020 Consolidated assets Total assets Maximum exposure to (in billions of yen) Asset-backed commercial paper/loan programs 2,045 — — Asset-backed securitizations 780 77 8 Investments in securitization products 370 — — Investment funds 2,283 2,346 483 Trust arrangements and other 5,557 — — Total 11,035 2,423 491
Unconsolidated VIEs
Schedule of Variable Interest Entities	The tables below present the carrying amounts and classification of assets and liabilities on the MHFG Group’s balance sheets that relate to its variable interests in significant unconsolidated VIEs, as of March 31, 2020 and September 30, 2020: Assets on balance sheets related to unconsolidated VIEs: March 31, 2020 September 30, 2020 (in billions of yen) Trading account assets 108 113 Investments 267 231 Loans 55 58 Total 430 402 Liabilities on balance sheets and maximum exposure to loss related to unconsolidated VIEs: March 31, 2020 September 30, 2020 (in billions of yen) Payables under securities lending transactions 47 48 Trading account liabilities 2 2 Total 49 50 Maximum exposure to loss (Note) 521 491 Note: This represents the maximum amount the Group could possibly be required to record in its consolidated statements of income associated with on-balance-sheet off-balance-sheet

Noninterest income (Tables)

Noninterest income (Tables)	6 Months Ended
	Sep. 30, 2020
Summary of Noninterest Income	Details of Noninterest income for t Six months ended September 30, 2019 2020 (in millions of yen) Fee and commission income: Securities-related business (1) 64,498 78,441 Deposits-related business (1) 7,570 7,408 Lending-related business (2)(4) 68,609 79,619 Remittance business (1) 56,075 54,785 Asset management business (1) 48,291 45,948 Trust-related business (1) 56,459 54,425 Agency business (1) 15,152 15,064 Guarantee-related business (3) 13,898 15,560 Fees for other customer services (1) 73,440 77,067 Total Fee and commission income 403,992 428,317 Foreign exchange gains (losses)—net (3) 27,923 22,785 Trading account gains (losses)—net (2) 395,405 257,591 Investment gains (losses)—net: Debt securities (3) 31,092 46 Equity securities (3) (126,648 ) 266,119 Equity in earnings (losses) of equity method investees-net (3) 22,066 5,788 Gains on disposal of premises and equipment (3) 1,693 6,849 Other noninterest income (2)(5) 34,839 23,715 Total 790,362 1,011,210 Notes: (1) These amounts are revenues from contracts within the scope of ASC 606, “Revenue from contracts with customers” (“ASC 606”). (2) Part of these amounts are considered to be revenues from contracts that are within the scope of ASC 606. (3) These amounts are revenues from contracts that do not meet the scope of ASC 606. (4) Most of the lending-related fees such as commitment fees and arrangement fees are not within the scope of ASC 606. (5) These amounts include the net unrealized gains resulting from changes in fair values of structured notes that contain embedded derivatives. See Note 17 “Fair value” for further details.

Fair value (Tables)

Fair value (Tables)	6 Months Ended
	Sep. 30, 2020
Summary of Assets and Liabilities Measured at Fair Value on a Recurring Basis, Including Fair Value Option Elected	Assets and liabilities measured at fair valu e March 31, 2020 Level 1 Level 2 Level 3 Assets/ Liabilities measured at fair value (in billions of yen) Assets: Trading securities (1) Japanese government bonds 1,516 22 — 1,538 Japanese local government bonds — 170 — 170 U.S. Treasury bonds and federal agency securities 4,580 461 — 5,041 Other foreign government bonds 1,128 547 — 1,675 Agency mortgage-backed securities — 3,390 — 3,390 Residential mortgage-backed securities — — 10 10 Certificates of deposit and commercial paper — 1,036 — 1,036 Corporate bonds and other (2) 41 1,398 1,115 2,554 Equity securities 1,000 650 30 1,680 Trading securities measured at net asset value (3) 462 Derivative financial instruments: Interest rate contracts 153 7,070 9 7,232 Foreign exchange contracts 9 2,900 17 2,926 Equity-related contracts 169 125 16 310 Credit-related contracts — 22 8 30 Other contracts 3 11 24 38 Available-for-sale Japanese government bonds 11,950 653 — 12,603 Japanese local government bonds — 273 — 273 U.S. Treasury bonds and federal agency securities 935 — — 935 Other foreign government bonds 436 975 — 1,411 Agency mortgage-backed securities — 505 — 505 Residential mortgage-backed securities — 53 31 84 Commercial mortgage-backed securities — — 615 615 Japanese corporate bonds and other debt securities — 1,678 157 1,835 Foreign corporate bonds and other debt securities — 678 174 852 Equity securities: Equity securities with readily determinable fair values 2,670 95 — 2,765 Equity securities measured at net asset value (3) 72 Other investments — — 39 39 Total assets measured at fair value on a recurring basis 24,590 22,712 2,245 50,081 Liabilities: Trading securities sold, not yet purchased 1,880 515 — 2,395 Derivative financial instruments: Interest rate contracts 163 6,611 14 6,788 Foreign exchange contracts 8 2,890 1 2,899 Equity-related contracts 186 47 33 266 Credit-related contracts — 19 10 29 Other contracts 6 10 23 39 Long-term debt (4) — 1,916 621 2,537 Total liabilities measured at fair value on a recurring basis 2,243 12,008 702 14,953 September 30, 2020 Level 1 Level 2 Level 3 Assets/ Liabilities measured at fair value (in billions of yen) Assets: Trading securities (1) Japanese government bonds 3,257 11 — 3,268 Japanese local government bonds — 138 — 138 U.S. Treasury bonds and federal agency securities 4,963 829 — 5,792 Other foreign government bonds 938 526 — 1,464 Agency mortgage-backed securities — 4,348 — 4,348 Residential mortgage-backed securities — — 9 9 Certificates of deposit and commercial paper — 1,259 — 1,259 Corporate bonds and other (2) 22 1,348 1,085 2,455 Equity securities 929 570 30 1,529 Trading securities measured at net asset value (3) 447 Derivative financial instruments: Interest rate contracts 40 6,088 7 6,135 Foreign exchange contracts — 2,123 20 2,143 Equity-related contracts 98 287 12 397 Credit-related contracts — 52 3 55 Other contracts 3 10 15 28 Available-for-sale Japanese government bonds 19,600 320 — 19,920 Japanese local government bonds — 407 — 407 U.S. Treasury bonds and federal agency securities 627 — — 627 Other foreign government bonds 430 926 — 1,356 Agency mortgage-backed securities — 520 — 520 Residential mortgage-backed securities — 53 27 80 Commercial mortgage-backed securities — — 641 641 Japanese corporate bonds and other debt securities — 1,579 491 2,070 Foreign corporate bonds and other debt securities — 747 178 925 Equity securities: Equity securities with readily determinable fair values 2,976 40 — 3,016 Equity securities measured at net asset value (3) 83 Other investments — — 56 56 Total assets measured at fair value on a recurring basis 33,883 22,181 2,574 59,168 Liabilities: Trading securities sold, not yet purchased 2,051 268 20 2,339 Derivative financial instruments: Interest rate contracts 39 5,679 10 5,728 Foreign exchange contracts — 2,159 1 2,160 Equity-related contracts 128 109 23 260 Credit-related contracts — 75 2 77 Other contracts 4 8 14 26 Long-term debt (4) — 2,164 638 2,802 Total liabilities measured at fair value on a recurring basis 2,222 10,462 708 13,392 Notes: (1) Trading securities include foreign currency denominated s (2) The amount includes CLO and convertible bonds, which are classified in Level 3. (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, 2020 and September 30, 2020 were ¥47 billion and ¥ 56 (4) Amounts represent items for which the Group elected the fair value option or for which it applied the practicability exception.
Reconciliation for All Assets and Liabilities Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs (Level 3)	The following table presents a reconciliation for all assets and liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) for the six months ended September 30, 2019 and 2020: Six months ended September 30, 2019 April 1, 2019 Gains (losses) in Earnings Gains (losses) in OCI Transfers into Level 3 Transfers out of Level 3 Purchases Sales Issuances Settle- ments September 30, 2019 Change in unrealized gains (losses) still held (6) (in billions of yen) Assets: Trading securities: Residential mortgage-backed securities 11 — (2) — — — — — — (1 ) 10 — Corporate bonds and other 1,044 (15 ) (2) — — — 338 (105 ) — (125 ) 1,137 (14 ) Equity securities 28 2 (2) — — — 1 — — (1 ) 30 — Derivative financial instruments, net (1) Interest rate contracts 13 (9 ) (2) — — — — — — 1 5 (8 ) Foreign exchange contracts 22 (10 ) (2) — — — — — — (2 ) 10 (9 ) Equity-related contracts (5 ) 1 (2) — — — — — — (3 ) (7 ) 2 Credit-related contracts 1 — (2) — — — — — — — 1 — Other contracts 1 — (2) — — — — — — — 1 — Available-for-sale Residential mortgage-backed securities 40 — (3) — (4) — — — — — (7 ) 33 — Commercial mortgage-backed securities 500 — (3) 1 (4) — — 89 (35 ) — (6 ) 549 — Japanese corporate bonds and other 120 1 (3) 4 (4) — — 97 — — (53 ) 169 — Foreign corporate bonds and other debt securities 103 — (3) (5 ) (4) — — 38 — — (3 ) 133 — Other investments 35 1 (3) — — — 10 — — (10 ) 36 2 Liabilities: Trading securities sold, not yet purchased 1 — (2) — — — (9 ) 8 — — — — Long-term debt 655 (6 ) (5) — (4) 17 (6 ) — — 108 (134 ) 646 (10 ) Six months ended September 30, 2020 April 1, 2020 Gains (losses) Earnings Gains (losses) OCI Transfers into Level 3 Transfers out of Level 3 Purchases Sales Issuances Settle- ments September 30, 2020 Change in unrealized gains (losses) still held (6) (in billions of yen) Assets: Trading securities: Residential mortgage-backed securities 10 — (2) — — — — — — (1 ) 9 — Corporate bonds and other 1,115 18 (2) — — (1 ) 189 (113 ) — (123 ) 1,085 18 Equity securities 30 (2 ) (2) — — — 2 — — — 30 (1 ) Derivative financial instruments, net (1) Interest rate contracts (5 ) (3 ) (2) — — — — — — 5 (3 ) 1 Foreign exchange contracts 16 4 (2) — — — — — — (1 ) 19 5 Equity-related contracts (17 ) 4 (2) — — — — — — 2 (11 ) 3 Credit-related contracts (2 ) 3 (2) — 1 1 — — — (2 ) 1 1 Other contracts 1 — (2) — — — — — — — 1 — Available-for-sale Residential mortgage-backed securities 31 — (3) — (4) — — — — — (4 ) 27 — Commercial mortgage-backed securities 615 — (3) 1 (4) — — 78 (51 ) — (2 ) 641 — Japanese corporate bonds and other debt securities 157 (7 ) (3) 8 (4) — — 344 — — (11 ) 491 — Foreign corporate bonds and other debt securities 174 1 (3) 8 (4) — — 31 — — (36 ) 178 — Other investments 39 (1 ) (3) — — — 38 (1 ) — (19 ) 56 (1 ) Liabilities: Trading securities sold, not yet purchased — — (2) — — — — 20 — — 20 — Long-term debt 621 (37 ) (5) (8 ) (4) 19 (35 ) — — 108 (120 ) 638 (27 ) Notes: (1) Total Level 3 derivative exposures have been netted on the table for presentation purposes only. (2) Gains (losses) in Earnings are reported in Trading account gains (losses)-net, (losses)-net (3) Gains (losses) in Earnings are reported in Investment gains (losses)-net. (4) Gains (losses) in OCI are reported in Other comprehensive income (loss). (5) Gains (losses) in Earnings are reported in Other noninterest income (expenses). (6) 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 September 30, 2019 and 2020. The amounts of unrealized gains (losses) in OCI related to Available-for-sale securities and Long-term debt were ¥7 billion and ¥(8) billion, at September 30, 2020, respectively.
Quantitative Information about Significant Unobservable Inputs Related to Material Classes of Level 3 Assets and Liabilities	Quantitative information about Level 3 fair value measurements The following table presents information about significant unobservable inputs related to the MHFG Group’s material classes of Level 3 assets and liabilities at March 31, 2020 and September 30, 2020: March 31, 2020 Products/Instruments Fair value Principal valuation technique Unobservable inputs Range of input values Weighted average (5) (in billions of yen, except for percentages and basis points) Trading securities and Available-for-sale Residential mortgage-backed securities 41 Discounted cash flow Price-based Prepayment rate Default rate Recovery rate Discount margin 4% - 16% 0% - 1% 100% - 100% 5bps - 170bps 7% 0% 100% 52bps Commercial mortgage-backed securities 615 Discounted cash flow Price-based Discount margin 7bps - 185bps 22bps Corporate bonds and other debt securities 1,446 Discounted cash flow Price-based Prepayment rate (1) Default rate (1) Recovery rate (1) Discount margin (1) Discount margin (2) 13% - 21% 0% - 2% 10% - 70% 61bps - 1,160bps 5bps - 1,528bps 21% 2% 67% 256bps 58bps Derivative financial instruments, net: Interest rate contracts (5 ) Internal valuation model (3) IR – IR correlation Default rate (4) 23% - 100% 0% - 63% Foreign exchange contracts 16 Internal valuation model (3) FX – IR correlation FX – FX correlation Default rate (4) -37% - 49% 56% - 65% 0% - 63% Equity-related contracts (17 ) Internal valuation model (3) Equity – IR correlation Equity correlation Equity volatility 25% - 25% 0% - 100% 13% - 157% Credit-related contracts (2 ) Internal valuation model (3) Default rate Credit correlation 0% - 15% 30% - 100% Long-term debt 621 Internal valuation model (3) IR – IR correlation FX – IR correlation FX – FX correlation Equity – IR correlation Equity – FX correlation Equity correlation Equity volatility Default rate Credit correlation 23% - 100% -37% - 50% 56% - 65% 25% - 25% -33% - 100% 0% - 100% 15% - 157% 0% - 12% 15% - 100% September 30, 2020 Products/Instruments Fair value Principal valuation technique Unobservable inputs Range of input values Average (5) (in billions of yen, except for percentages and basis points) Trading securities and Available-for-sale securities: Residential mortgage-backed securities 36 Discounted cash flow Price-based Prepayment rate Default rate Recovery rate Discount margin 3% - 16% 0% - 1% 100% - 100% 5bps - 170bps 7% 0% 100% 50bps Commercial mortgage-backed securities 641 Discounted cash flow Price-based Discount margin 6bps - 185bps 21bps Corporate bonds and other debt securities 1,754 Discounted cash flow Price-based Prepayment rate (1) Default rate (1) Recovery rate (1) Discount margin (1) Discount margin (2) 1% - 22% 0% - 3% 10% - 69% 25bps - 173bps 4bps - 696bps 19% 1% 67% 123bps 233bps Derivative financial instruments, net: Interest rate contracts (3) Internal valuation model (3) IR - IR correlation 23% - 100% 76% Foreign exchange contracts 19 Internal valuation model (3) FX - IR correlation FX - FX correlation -27% -52% 46% - 63% 28% 55% Equity-related contracts (11) Internal valuation model (3) Equity - IR correlation Equity correlation Equity volatility 25% - 25% 0% - 100% 12% - 96% 25% 88% 43% Credit-related contracts 1 Internal valuation model (3) Default rate Credit correlation 0% - 7% 35% - 100% 1% 66% Other contracts 1 Internal valuation model (3) Commodity volatility 0% - 57% 36% Long-term debt 638 Internal valuation model (3) IR - IR correlation FX - IR correlation FX - FX correlation Equity - IR correlation Equity - FX correlation Equity correlation Equity volatility Default rate Credit correlation 23% - 100% -27% - 52% 46% - 63% 25% - 25% -33% - 100% 0% - 100% 13% - 96% 0% - 6% 18% - 100% 76% 35% 55% 25% -3% 86% 29% 2% 66% Notes: (1) These inputs are mainly used for determining the fair values of securitization products such as CDO, CLO and ABS, other than RMBS and CMBS. (2) This input is mainly used for determining the fair values of Japanese corporate bonds and foreign corporate bonds. (3) Internal valuation model includes discounted cash flow models and the Black-Scholes option pricing model. (4) This input represents the counterparty default rate derived from the MHFG Group’s own internal credit analyses. (5) 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. IR = Interest rate FX = Foreign exchange
Summary of Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis	The following table shows the fair value hierarchy for these items as of March 31, 2020 and September 30, 2020: March 31, 2020 Total Level 1 Level 2 Level 3 Aggregate (in billions of yen) Assets: Loans 90 — — 90 136 Loans held-for-sale 26 — 20 6 26 Equity securities (without readily determinable fair values) 2 — — 2 2 Premises and equipment - 1 — 1 — 12 Other assets — — — — 3 Goodwill — — — — 2 Total assets measured at fair value on a nonrecurring basis 119 — 21 98 181 September 30, 2020 Total Level 1 Level 2 Level 3 Aggregate (in billions of yen) Assets: Loans 131 — 2 129 200 Loans held-for-sale 17 — 11 6 18 Equity securities (without readily determinable fair values) 1 — — 1 2 Other investment s 52 31 — 21 59 Premises and equipment - — — — — 1 Total assets measured at fair value on a nonrecurring basis 201 31 13 157 280 Note: The fair values may not be current as of the dates indicated, but rather as of the date the fair value change occurred. Accordingly, the carrying values may not equal current fair value.
Carrying Amounts and Fair Values of Certain Financial Instruments, Excluding Financial Instruments Carried at Fair Value on a Recurring Basis and Those outside Scope of ASC 825	The following table shows the carrying amounts an d March 31, 2020 Carrying amount Estimated fair value Total Level 1 Level 2 Level 3 (in billions of yen) Financial assets: Cash and due from banks, interest-bearing deposits in other banks, call loans and funds sold, and receivables under resale agreements and securities borrowing 63,755 63,755 1,318 62,437 — Investments 862 875 493 382 — Loans, net of allowance (Note) 86,914 88,124 — — 88,124 Financial liabilities: Noninterest-bearing deposits, call money and funds purchased, and payables under repurchase agreements and securities lending transactions 51,954 51,954 29,812 22,142 — Interest-bearing deposits 114,653 114,659 58,935 55,724 — Due to trust accounts 250 250 — 250 — Other short-term borrowings 4,914 4,914 — 4,914 — Long-term debt 7,821 7,708 — 6,813 895 September 30, 2020 Carrying amount Estimated fair value Total Level 1 Level 2 Level 3 (in billions of yen) Financial assets: Cash and due from banks, interest-bearing deposits in other banks, call loans and funds sold, and receivables under resale agreements and securities borrowing 58,623 58,623 42,233 16,390 — Investments 790 812 491 321 — Loans, net of allowance (Note) 89,611 90,983 — — 90,983 Financial liabilities: Noninterest-bearing deposits, call money and funds purchased, and payables under repurchase agreements and securities lending transactions 53,640 53,640 — 53,640 — Interest-bearing deposits 118,333 118,347 — 118,347 — Due to trust accounts 564 564 — 564 — Other short-term borrowings 7,526 7,526 — 7,526 — Long-term debt 8,266 8,493 — 7,155 1,338 Note: Loans, net of allowance include items measured at fair value on a nonrecurring basis.

Offsetting of financial asset_2

Offsetting of financial assets and financial liabilities (Tables)	6 Months Ended
	Sep. 30, 2020
Information of Offsetting of Financial Assets and Financial Liabilities	The following table p Amounts not offset on the balance sheet (3) Gross amounts recognized Gross amounts offset on the balance sheet Net amounts presented on the balance sheet (2) Financial instruments (4) Cash collateral Net amounts (in billions of yen) March 31, 2020 Assets (1) Derivatives 9,819 — 9,819 (7,723 ) (629 ) 1,467 Receivables under resale agreements 17,347 — 17,347 (17,197 ) — 150 Receivables under securities borrowing transactions 1,753 — 1,753 (1,709 ) — 44 Total 28,919 — 28,919 (26,629 ) (629 ) 1,661 Liabilities (1) Derivatives 9,220 — 9,220 (7,519 ) (1,215 ) 486 Payables under repurchase agreements 17,542 — 17,542 (17,191 ) — 351 Payables under securities lending transactions 626 — 626 (623 ) — 3 Total 27,388 — 27,388 (25,333 ) (1,215 ) 840 September 30, 2020 Assets: Derivatives 8,758 — 8,758 ( 5 (6,373 ) (486 ) 1,899 Receivables under resale agreements 12,666 — 12,666 ( 6 (11,479 ) — 1,187 Receivables under securities borrowing transactions 2,186 — 2,186 ( 7 (1,846 ) — 340 Total 23,610 — 23,610 (19,698 ) (486 ) 3,426 Liabilities: Derivatives 8,251 — 8,251 ( 5 (6,148 ) (930 ) 1,173 Payables under repurchase agreements 19,326 — 19,326 ( 6 (18,038 ) — 1,288 Payables under securities lending 1,476 — 1,476 ( 7 (1,235 ) — 241 Total 29,053 — 29,053 (25,421 ) (930 ) 2,702 Notes: (1) 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. (2) Derivative assets and liabilities are recorded in Trading account assets and Trading account liabilities, respectively. (3) Amounts do not exceed the net amounts presented on the balance sheet and do not include the effect of overcollateralization, where it exists. (4) For derivatives, amounts include derivative assets or liabilities and securities collateral that are eligible for offsetting under enforceable master netting arrangements or similar agreements. (5) The amounts of derivative assets and liabilities subject to enforceable master netting arrangements or similar agreements at September 30, 2020 were ¥8,154 billion and ¥7,528 billion, respectively. (6) The amounts of Receivables under resale agreements and Payables under repurchase agreements subject to enforceable industry standard master repurchase agreements with netting terms at September 30, 2020 were ¥11,490 billion and ¥18,755 billion, respectively . (7) 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 at September 30, 2020 were ¥1,915 billion and ¥1,243 billion, respectively .

Repurchase agreements and sec_2

Repurchase agreements and securities lending transactions accounted for as secured borrowings (Tables)	6 Months Ended
	Sep. 30, 2020
Gross Amounts of Liabilities by Remaining Contractual Maturity	The following table shows the gross amounts of liabilities associated with repurchase agreements and securities lending transactions, by remaining contractual maturity at March 31, 2020 and September 30, 2020: Overnight and continuous Up to 30 days 31-90 days Greater than 90 days Total (in billions of yen) March 31, 2020 Repurchase agreements 6,357 5,467 4,867 1,280 17,971 Securities lending transactions 877 231 — 316 1,424 Total 7,234 5,698 4,867 1,596 19,395 September 30, 2020 Repurchase agreements 10,154 3,684 3,162 2,326 19,326 Securities lending transactions 798 298 50 330 1,476 Total 10,952 3,982 3,212 2,656 20,802
Gross Amounts of Liabilities by Class of Underlying Collateral	The following table shows the gross amounts of liabilities associated with repurchase agreements and securities lending transactions, by class of underlying collateral at March 31, 2020 and September 30, 2020: Repurchase agreements Securities lending transactions (in billions of yen) March 31, 2020 Japanese government bonds and Japanese local government bonds 1,790 269 Foreign government bonds and foreign agency mortgage-backed securities 15,218 359 Commercial paper and corporate bonds 273 50 Equity securities 542 730 Other 148 16 Total (Note) 17,971 1,424 September 30, 2020 Japanese government bonds and Japanese local government bonds 3,355 372 Foreign government bonds and foreign agency mortgage-backed securities 15,100 368 Commercial paper and corporate bonds 209 53 Equity securities 579 668 Other 83 15 Total (Note) 19,326 1,476 Note: Amounts exceeded the gross amounts recognized in Note 18 “Offsetting of financial assets and financial liabilities” by ¥1,227 billion and ¥804 billion, at March 31, 2020 and September 30, 2020, respectively, which excluded the amounts relating to master netting agreements or similar agreements where the MHFG Group did not have the legal right of set-off

Business segment information (T

Business segment information (Tables)	6 Months Ended
	Sep. 30, 2020
Reportable Segment Information Derived from Internal Management Reporting Systems, on Basis of Japanese GAAP	The reportable segment information, set forth below, is derived from the internal management reporting systems used by management to measure the performance of the Group’s operating segments. Management measures the performance of each of the operating segments in accordance with internal managerial accounting rules and practices. In addition, the format and information are presented primarily on the basis of Japanese GAAP. Therefore, they are not consistent with the consolidated financial statements prepared in accordance with U.S. GAAP. A reconciliation is provided for the total amount of all business segments’ “Net business profits (losses) + Net gains (losses) related to ETFs and others” with income before income tax expense under U.S. GAAP, and the total amount of all business segments’ “Fixed assets” with the total amount of Premises and equipment-net, right-of-use MHFG (Consolidated) Six months ended September 30, 2019 (1) Retail & Business Banking Company Corporate & Institutional Company Global Corporate Company Global Markets Company Asset Management Company Others (6) Total (in billions of yen) Gross profits + Net gains (losses) related to ETFs and others (2) 322.0 220.2 203.9 235.0 25.5 16.2 1,022.8 General and administrative expenses (3) 330.7 104.0 118.6 101.4 16.4 17.3 688.4 Equity in earnings (losses) of equity method investees—net 6.4 1.1 6.0 — 0.5 5.0 19.0 Amortization of goodwill and others 1.4 0.1 0.2 0.5 3.9 0.5 6.6 Others — — — — — (5.9 ) (5.9 ) Net business profits (losses) (4) (3.7 ) 117.2 91.1 133.1 5.7 (2.5 ) 340.9 Fixed assets (5) 508.2 208.4 160.1 92.8 0.1 732.0 1,701.6 MHFG Six months ended September 30, 2020 Retail & Business Banking Company Corporate & Institutional Company Global Corporate Company Global Markets Company Asset Management Company Others (6) Total (in billions of yen) Gross profits + Net gains (losses) related to ETFs and others (2) 307.4 234.2 222.6 291.5 23.6 14.0 1,093.3 General and administrative expenses (3) 315.0 104.6 121.4 105.6 15.7 17.0 679.3 Equity in earnings (losses) of equity method investees—net 3.6 2.4 5.8 — 0.4 (0.7 ) 11.5 Amortization of goodwill and others 1.1 0.1 0.2 0.4 3.8 0.5 6.1 Net business profits (losses) (4) (5.1 ) 131.9 106.8 185.5 4.5 (4.2 ) 419.4 Fixed assets (5) 518.5 186.3 157.0 90.9 0.1 768.5 1,721.3 Notes: (1) 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. (2) “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 non-consolidated (3) “General and administrative expenses” excludes non-allocated (4) 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 (5) “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; right-of-use (6) “Others” includes the following items: • profits and expenses pertaining to consolidated subsidiaries that are not subject to allocation; • consolidating adjustments, including elimination • equity in earnings (losses) of equity method investees-net • profits and losses pertaining to derivative transactions that reflect the counterparty risk of the individual parties and other factors in determining fair market value. F-73
Reconciliation of Total Net Business Profits under Internal Management Reporting Systems to Income Before Income Tax Expense on Consolidated Statements of Income	A reconciliation of “Net business profits (losses) + Net gains (losses) related to ETFs and others” for the six months ended September 30, 2019 and 2020 presented above to income before income tax expense shown on the consolidated statements of income and a reconciliation of “Fixed assets” at September 30, 2019 and 2020 to the total amount of Premises and equipment - right-of-use Six months ended September 30, 2019 (in billions of yen) Net business profits (losses) + Net gains (losses) related to ETFs and others 340.9 419.4 Adjustment to reconcile management reporting to Japanese GAAP: General and administrative expenses: non-allocated 24.5 4.1 Expenses related to portfolio problems (including reversal of (provision for) general reserve for losses on loans) (19.1 ) (84.8 ) Gains on reversal of reserves for possible losses on loans, and others 7.9 3.6 Net gains (losses) related to stocks—Net gains (losses) related to ETFs and others 55.4 (50.5 ) Net extraordinary gains (losses) (5.0 ) 65.8 Others (13.1 ) (24.2 ) Income before income tax expense under Japanese GAAP 391.5 333.4 Adjustment to reconcile Japanese GAAP to U.S. GAAP: Derivative financial instruments and hedging activities 105.0 (12.9 ) Investments (163.9 ) 285.4 Loans — (10.8 ) Allowances for credit losses (1) 0.5 35.8 Premises and equipment (51.5 ) (37.1 ) Land revaluation 0.5 2.7 Business combinations 4.1 (4.3 ) Pension liabilities (27.3 ) (84.5 ) Consolidation of variable interest entities 40.3 36.6 Foreign currency translation 14.3 (0.2 ) Others (3.0 ) 3.7 Income before income tax expense under U.S. GAAP 310.5 547.8
Reconciliation of Assets from Segment to Consolidated	As of September 30, (in billions of yen) Fixed assets 1,701.6 1,721.3 U.S. GAAP adjustments (2) 964.5 818.4 Premises and equipment-net right-of-use 2,666.1 2,539.7 Notes: (1) The MHFG Group adopted ASU No.2016-13, 2019-04, 2019-05, 2019-11 off-balance-sheet (2) The U.S. GAAP adjustments are primarily comprised of GAAP differences mainly from right-of-use

Basis of presentation - Additio

Basis of presentation - Additional Information (Detail)	Jun. 25, 2020
Disclosure of Accounting Policies [Line Items]
Stockholders equity stock consolidation	1-for-10 share

Issued accounting pronounceme_3

Issued accounting pronouncements - Additional Information (Detail) $ in Billions	Apr. 01, 2020USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Financing receivable, allowance for credit loss, period increase (decrease)	$ 176
Fresh-start adjustment, increase (decrease), retained earnings (deficit)	$ 125

Issued accounting pronounceme_4

Issued accounting pronouncements - Summary of Accounting Standards Update and Change in Accounting Principle (Detail) - JPY (¥) ¥ in Millions	Sep. 30, 2020	Apr. 01, 2020	Mar. 31, 2020	Sep. 30, 2019	Mar. 31, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans and leases receivable, allowance	¥ 622,526		¥ 440,855	¥ 291,422	¥ 307,201
Off-balance sheet, credit loss, liability			46,000
Corporate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans and leases receivable, allowance	530,519		413,026	263,291	277,955
Retail
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans and leases receivable, allowance	¥ 92,007		27,829	¥ 28,131	¥ 29,246
Cumulative effect of change in accounting principles
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans and leases receivable, allowance			155,755
Off-balance sheet, credit loss, liability		¥ 20,000
Cumulative effect of change in accounting principles | Corporate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans and leases receivable, allowance		78,000	77,514
Cumulative effect of change in accounting principles | Retail
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans and leases receivable, allowance		78,000	78,241
Cumulative effect, period of adoption, adjusted balance
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans and leases receivable, allowance			596,610
Off-balance sheet, credit loss, liability		66,000
Cumulative effect, period of adoption, adjusted balance | Corporate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans and leases receivable, allowance		491,000	490,540
Cumulative effect, period of adoption, adjusted balance | Retail
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans and leases receivable, allowance		¥ 106,000	¥ 106,070

Investments - Amortized Cost, G

Investments - Amortized Cost, Gross Unrealized Gains and Losses, and Fair Value of Available-for-Sale and Held-to-Maturity Securities (Detail) - JPY (¥) ¥ in Millions		Sep. 30, 2020	Mar. 31, 2020
Schedule of Investments [Line Items]
Amortized cost, net available-for-sale securities	[1],[2]	¥ 26,562,414	¥ 19,132,999
Gross unrealized gains, available-for-sale securities		40,782	40,504
Gross unrealized losses, available-for-sale securities		56,396	60,551
Fair value, available-for-sale securities		26,546,800	19,112,952
Amortized cost, held-to-maturity securities	[1],[2]	789,978	862,031
Gross unrealized gains, held-to-maturity securities		22,171	14,602
Gross unrealized losses, held-to-maturity securities		0	1,303
Total		812,149	875,330
Debt securities | Japanese government bonds
Schedule of Investments [Line Items]
Amortized cost, net available-for-sale securities	[1],[2]	19,964,553	12,651,677
Gross unrealized gains, available-for-sale securities		1,084	1,319
Gross unrealized losses, available-for-sale securities		45,274	50,224
Fair value, available-for-sale securities		19,920,363	12,602,772
Amortized cost, held-to-maturity securities	[1],[2]	479,947	479,936
Gross unrealized gains, held-to-maturity securities		11,505	13,357
Gross unrealized losses, held-to-maturity securities		0
Total		491,452	493,293
Debt securities | Japanese local government bonds
Schedule of Investments [Line Items]
Amortized cost, net available-for-sale securities	[1],[2]	406,873	272,412
Gross unrealized gains, available-for-sale securities		757	649
Gross unrealized losses, available-for-sale securities		446	494
Fair value, available-for-sale securities		407,184	272,567
Debt securities | U.S. Treasury bonds and federal agency securities
Schedule of Investments [Line Items]
Amortized cost, net available-for-sale securities	[1],[2]	625,398	927,172
Gross unrealized gains, available-for-sale securities		1,388	7,733
Gross unrealized losses, available-for-sale securities		2
Fair value, available-for-sale securities		626,784	934,905
Debt securities | Other foreign government bonds
Schedule of Investments [Line Items]
Amortized cost, net available-for-sale securities	[1],[2]	1,353,376	1,408,009
Gross unrealized gains, available-for-sale securities		3,020	3,273
Gross unrealized losses, available-for-sale securities		74	202
Fair value, available-for-sale securities		1,356,322	1,411,080
Debt securities | Agency mortgage-backed securities
Schedule of Investments [Line Items]
Amortized cost, net available-for-sale securities	[3]	509,808	494,958
Gross unrealized gains, available-for-sale securities	[3]	10,650	10,490
Gross unrealized losses, available-for-sale securities	[3],[4]	433	434
Fair value, available-for-sale securities	[3]	520,025	505,014
Amortized cost, held-to-maturity securities	[5]	310,031	382,095
Gross unrealized gains, held-to-maturity securities	[5]	10,666	1,245
Gross unrealized losses, held-to-maturity securities	[5]	0	1,303
Total	[5]	320,697	382,037
Debt securities | Residential mortgage-backed securities
Schedule of Investments [Line Items]
Amortized cost, net available-for-sale securities	[1],[2]	78,883	83,077
Gross unrealized gains, available-for-sale securities		1,220	1,405
Gross unrealized losses, available-for-sale securities		123	151
Fair value, available-for-sale securities		79,980	84,331
Debt securities | Commercial mortgage-backed securities
Schedule of Investments [Line Items]
Amortized cost, net available-for-sale securities	[1],[2]	634,537	609,559
Gross unrealized gains, available-for-sale securities		6,674	5,551
Gross unrealized losses, available-for-sale securities		69	106
Fair value, available-for-sale securities		641,142	615,004
Debt securities | Japanese corporate bonds and other debt securities
Schedule of Investments [Line Items]
Amortized cost, net available-for-sale securities	[6]	2,066,234	1,836,540
Gross unrealized gains, available-for-sale securities	[6]	12,579	7,489
Gross unrealized losses, available-for-sale securities	[6]	8,785	8,772
Fair value, available-for-sale securities	[6]	2,070,028	1,835,257
Debt securities | Foreign corporate bonds and other debt securities
Schedule of Investments [Line Items]
Amortized cost, net available-for-sale securities	[7]	922,752	849,595
Gross unrealized gains, available-for-sale securities	[7]	3,410	2,595
Gross unrealized losses, available-for-sale securities	[7]	1,190	168
Fair value, available-for-sale securities	[7]	¥ 924,972	¥ 852,022
[1]	Accrued interest receivables are excluded from amortized cost, of which the amount was ¥4,153 million at September 30, 2020 and included in Accrued income.
[2]	Amortized cost, net of the allowance for credit losses, of which the amounts related to available-for-sale securities was ¥7,551 million at September 30, 2020.
[3]	Agency mortgage-backed securities presented in this line consist of Japanese and Foreign agency mortgage-backed securities, of which the fair values were ¥504,953 million and ¥61 million, respectively, at March 31, 2020, and ¥519,974 million and ¥51 million, respectively, at September 30, 2020. 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.
[4]	Agency mortgage-backed securities presented in this line consist of Japanese and Foreign agency mortgage-backed securities, of which the fair values were ¥40,417 million and ¥0 million, respectively, at March 31, 2020, and ¥0 million and ¥0 million, respectively, at September 30, 2020. 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 Ginnie Mae securities, which are guaranteed by the United States government.
[5]	All Agency mortgage-backed securities presented in this line are Ginnie Mae securities.
[6]	Other debt securities presented in this line primarily consist of Japanese asset-backed securities (“ABS”), of which the total fair values was ¥139,888 million at September 30, 2020.
[7]	Other debt securities presented in this line primarily consist of Foreign negotiable certificates of deposit (“NCDs”) and ABS, of which the total fair values were ¥271,387 million at March 31, 2020, and ¥319,044 million at September 30, 2020.

Investments - Amortized Cost,_2

Investments - Amortized Cost, Gross Unrealized Gains and Losses, and Fair Value of Available-for-Sale and Held-to-Maturity Securities (Parenthetical) (Detail) - JPY (¥) ¥ in Millions		Sep. 30, 2020	Mar. 31, 2020
Schedule of Investments [Line Items]
Fair value, available-for-sale securities		¥ 26,546,800	¥ 19,112,952
Amortised cost net of allowance for credit loss available for sale securities	[1],[2]	26,562,414	19,132,999
Net of Allowance for Credit Loss [Member]
Schedule of Investments [Line Items]
Amortised cost net of allowance for credit loss available for sale securities		7,551
Debt securities | Agency mortgage-backed securities
Schedule of Investments [Line Items]
Fair value, available-for-sale securities	[3]	520,025	505,014
Amortised cost net of allowance for credit loss available for sale securities	[3]	509,808	494,958
Debt securities | Negotiable certificates of deposits, asset- backed securities and collateral loan obligations
Schedule of Investments [Line Items]
Fair value, available-for-sale securities		319,044	271,387
Debt securities | Japanese agency mortgage-backed securities | Agency mortgage-backed securities
Schedule of Investments [Line Items]
Fair value, available-for-sale securities		519,974	504,953
Debt securities | Foreign agency mortgage-backed securities | Agency mortgage-backed securities
Schedule of Investments [Line Items]
Fair value, available-for-sale securities		51	61
Foreign government and corporate debt securities | Japanese agency mortgage-backed securities
Schedule of Investments [Line Items]
Fair value, available-for-sale securities			¥ 139,888
Available-for sale and held-to-maturity securities | Accrued Income [Member]
Schedule of Investments [Line Items]
Accrued interest receivables		¥ 4,153
[1]	Accrued interest receivables are excluded from amortized cost, of which the amount was ¥4,153 million at September 30, 2020 and included in Accrued income.
[2]	Amortized cost, net of the allowance for credit losses, of which the amounts related to available-for-sale securities was ¥7,551 million at September 30, 2020.
[3]	Agency mortgage-backed securities presented in this line consist of Japanese and Foreign agency mortgage-backed securities, of which the fair values were ¥504,953 million and ¥61 million, respectively, at March 31, 2020, and ¥519,974 million and ¥51 million, respectively, at September 30, 2020. 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.

Investments - Amortized Cost an

Investments - Amortized Cost and Fair Value of Available-for-Sale and Held-to-Maturity Securities by Contractual Maturity (Detail) - JPY (¥) ¥ in Millions		Sep. 30, 2020	Mar. 31, 2020
Investments Classified by Contractual Maturity Date [Line Items]
Due in one year or less, amortized cost		¥ 16,822,180
Due after one year through five years, amortized cost		5,582,146
Due after five years through ten years,amortized cost		2,787,606
Due after ten years, amortized cost		1,370,482
Total		26,562,414
Due after one year through five years, amortized cost		479,947
Due after ten years, amortized cost		310,031
Amortized cost, held-to-maturity securities	[1],[2]	789,978	¥ 862,031
Due in one year or less, fair value		16,824,447
Due after one year through five years, fair value		5,576,112
Due after five years through ten years, fair value		2,763,293
Due after ten years, fair value		1,382,948
Total		26,546,800
Due after one year through five years, fair value		491,452
Due after ten years, fair value		320,697
Total		812,149	875,330
Debt securities | Japanese government bonds
Investments Classified by Contractual Maturity Date [Line Items]
Due in one year or less, amortized cost		14,588,119
Due after one year through five years, amortized cost		3,630,141
Due after five years through ten years,amortized cost		1,550,745
Due after ten years, amortized cost		195,548
Total		19,964,553
Due after one year through five years, amortized cost		479,947
Amortized cost, held-to-maturity securities	[1],[2]	479,947	479,936
Due in one year or less, fair value		14,586,652
Due after one year through five years, fair value		3,619,928
Due after five years through ten years, fair value		1,522,868
Due after ten years, fair value		190,915
Total		19,920,363
Due after one year through five years, fair value		491,452
Total		491,452	493,293
Debt securities | Japanese local government bonds
Investments Classified by Contractual Maturity Date [Line Items]
Due in one year or less, amortized cost		30,537
Due after one year through five years, amortized cost		209,317
Due after five years through ten years,amortized cost		149,994
Due after ten years, amortized cost		17,025
Total		406,873
Due in one year or less, fair value		30,553
Due after one year through five years, fair value		209,557
Due after five years through ten years, fair value		149,982
Due after ten years, fair value		17,092
Total		407,184
Debt securities | U.S. Treasury bonds and federal agency securities
Investments Classified by Contractual Maturity Date [Line Items]
Due in one year or less, amortized cost		625,398
Total		625,398
Due in one year or less, fair value		626,784
Total		626,784
Debt securities | Other foreign government bonds
Investments Classified by Contractual Maturity Date [Line Items]
Due in one year or less, amortized cost		1,024,723
Due after one year through five years, amortized cost		326,539
Due after five years through ten years,amortized cost		1,058
Due after ten years, amortized cost		1,056
Total		1,353,376
Due in one year or less, fair value		1,025,928
Due after one year through five years, fair value		328,280
Due after five years through ten years, fair value		1,058
Due after ten years, fair value		1,056
Total		1,356,322
Debt securities | Agency mortgage-backed securities
Investments Classified by Contractual Maturity Date [Line Items]
Due after ten years, amortized cost		509,808
Total		509,808
Due after ten years, amortized cost		310,031
Amortized cost, held-to-maturity securities	[3]	310,031	382,095
Due after ten years, fair value		520,025
Total		520,025
Due after ten years, fair value		320,697
Total	[3]	320,697	¥ 382,037
Debt securities | Residential mortgage-backed securities
Investments Classified by Contractual Maturity Date [Line Items]
Due after ten years, amortized cost		78,883
Total		78,883
Due after ten years, fair value		79,980
Total		79,980
Debt securities | Commercial mortgage-backed securities
Investments Classified by Contractual Maturity Date [Line Items]
Due in one year or less, amortized cost		6,080
Due after one year through five years, amortized cost		252,315
Due after five years through ten years,amortized cost		375,342
Due after ten years, amortized cost		800
Total		634,537
Due in one year or less, fair value		6,085
Due after one year through five years, fair value		254,025
Due after five years through ten years, fair value		380,219
Due after ten years, fair value		813
Total		641,142
Debt securities | Japanese corporate bonds and other debt securities
Investments Classified by Contractual Maturity Date [Line Items]
Due in one year or less, amortized cost		94,088
Due after one year through five years, amortized cost		820,338
Due after five years through ten years,amortized cost		587,344
Due after ten years, amortized cost		564,464
Total		2,066,234
Due in one year or less, fair value		94,089
Due after one year through five years, fair value		819,848
Due after five years through ten years, fair value		585,922
Due after ten years, fair value		570,169
Total		2,070,028
Debt securities | Foreign corporate bonds and other debt securities
Investments Classified by Contractual Maturity Date [Line Items]
Due in one year or less, amortized cost		453,235
Due after one year through five years, amortized cost		343,496
Due after five years through ten years,amortized cost		123,123
Due after ten years, amortized cost		2,898
Total		922,752
Due in one year or less, fair value		454,356
Due after one year through five years, fair value		344,474
Due after five years through ten years, fair value		123,244
Due after ten years, fair value		2,898
Total		¥ 924,972
[1]	Accrued interest receivables are excluded from amortized cost, of which the amount was ¥4,153 million at September 30, 2020 and included in Accrued income.
[2]	Amortized cost, net of the allowance for credit losses, of which the amounts related to available-for-sale securities was ¥7,551 million at September 30, 2020.
[3]	All Agency mortgage-backed securities presented in this line are Ginnie Mae securities.

Investments - Additional Inform

Investments - Additional Information (Detail) - JPY (¥) ¥ in Millions	6 Months Ended
	Sep. 30, 2020	Mar. 31, 2020
Gain (Loss) on Securities [Line Items]
Equity method Investments, carrying value	¥ 412,281	¥ 404,513
Credit losses on available-for-sale securities	8,000
Held-to-maturity Securities
Gain (Loss) on Securities [Line Items]
Impairment loss on securities	¥ 0
Orient Corporation
Gain (Loss) on Securities [Line Items]
Percentage of proportionate share to the total outstanding common stock	49.00%
Chiba Kogya Bank LTD [Member]
Gain (Loss) on Securities [Line Items]
Percentage of proportionate share to the total outstanding common stock	16.89%
Joint Stock Commercial Bank Foreign Trade of Vietnam [Member]
Gain (Loss) on Securities [Line Items]
Percentage of proportionate share to the total outstanding common stock	15.00%
Mizuho Leasing Company LTD [Member]
Gain (Loss) on Securities [Line Items]
Percentage of proportionate share to the total outstanding common stock	23.52%
Matthew International Capital Management LLC [Member]
Gain (Loss) on Securities [Line Items]
Percentage of proportionate share to the total outstanding common stock	16.41%
Custody Bank of Japan Ltd [Member]
Gain (Loss) on Securities [Line Items]
Percentage of proportionate share to the total outstanding common stock	27.00%
Equity securities (marketable)
Gain (Loss) on Securities [Line Items]
Equity method Investments, carrying value	¥ 215,059	213,243
Equity method Investments, aggregated market values	¥ 344,131	¥ 287,488

Investments - Gross Unrealized

Investments - Gross Unrealized Losses and Fair Value of Available-for-Sale and Held-to-Maturity Securities, Aggregated by Length of Time that Individual Securities Have Been in a Continuous Unrealized Loss Position (Detail) - JPY (¥) ¥ in Millions		Sep. 30, 2020	Mar. 31, 2020
Gain (Loss) on Securities [Line Items]
Less than 12 months, Fair value, available-for-sale securities		¥ 11,269,398	¥ 11,576,157
Less than 12 months Gross unrealized losses, available-for-sale securities		28,679	49,870
12 months or more Fair value, available-for-sale securities		1,934,619	954,032
12 months or more Gross unrealized losses, available-for-sale securities		27,717	10,681
Total Fair value, available-for-sale securities		13,204,017	12,530,189
Total Gross unrealized losses, available-for-sale securities		56,396	60,551
Less than 12 months, Fair value, held-to-maturity securities		0
Less than 12 months Gross unrealized losses, held-to-maturity securities		0
12 months or more Fair value, held-to-maturity securities		0	191,244
12 months or more Gross unrealized losses, held-to-maturity securities		0	1,303
Total Fair value, held-to-maturity securities		0	191,244
Total Gross unrealized losses, held-to-maturity securities		0	1,303
Debt securities | Japanese government bonds
Gain (Loss) on Securities [Line Items]
Less than 12 months, Fair value, available-for-sale securities		9,978,136	10,339,320
Less than 12 months Gross unrealized losses, available-for-sale securities		23,884	43,204
12 months or more Fair value, available-for-sale securities		1,234,118	283,561
12 months or more Gross unrealized losses, available-for-sale securities		21,390	7,020
Total Fair value, available-for-sale securities		11,212,254	10,622,881
Total Gross unrealized losses, available-for-sale securities		45,274	50,224
Total Gross unrealized losses, held-to-maturity securities		0
Debt securities | Japanese local government bonds
Gain (Loss) on Securities [Line Items]
Less than 12 months, Fair value, available-for-sale securities		126,991	162,665
Less than 12 months Gross unrealized losses, available-for-sale securities		246	418
12 months or more Fair value, available-for-sale securities		72,086	34,114
12 months or more Gross unrealized losses, available-for-sale securities		200	76
Total Fair value, available-for-sale securities		199,077	196,779
Total Gross unrealized losses, available-for-sale securities		446	494
Debt securities | U.S. Treasury bonds and federal agency securities
Gain (Loss) on Securities [Line Items]
Less than 12 months, Fair value, available-for-sale securities		29,093
Less than 12 months Gross unrealized losses, available-for-sale securities		2
12 months or more Fair value, available-for-sale securities		0
12 months or more Gross unrealized losses, available-for-sale securities		0
Total Fair value, available-for-sale securities		29,093
Total Gross unrealized losses, available-for-sale securities		2
Debt securities | Other foreign government bonds
Gain (Loss) on Securities [Line Items]
Less than 12 months, Fair value, available-for-sale securities		278,022	196,990
Less than 12 months Gross unrealized losses, available-for-sale securities		74	202
12 months or more Fair value, available-for-sale securities		0
12 months or more Gross unrealized losses, available-for-sale securities		0
Total Fair value, available-for-sale securities		278,022	196,990
Total Gross unrealized losses, available-for-sale securities		74	202
Debt securities | Agency mortgage-backed securities
Gain (Loss) on Securities [Line Items]
Less than 12 months, Fair value, available-for-sale securities		30,948	30,913
Less than 12 months Gross unrealized losses, available-for-sale securities		202	227
12 months or more Fair value, available-for-sale securities	[1]	9,799	9,504
12 months or more Gross unrealized losses, available-for-sale securities	[1]	231	207
Total Fair value, available-for-sale securities	[1]	40,747	40,417
Total Gross unrealized losses, available-for-sale securities	[1],[2]	433	434
Less than 12 months, Fair value, held-to-maturity securities	[3]	0
Less than 12 months Gross unrealized losses, held-to-maturity securities	[3]	0
12 months or more Fair value, held-to-maturity securities	[3]	0	191,244
12 months or more Gross unrealized losses, held-to-maturity securities	[3]	0	1,303
Total Fair value, held-to-maturity securities	[3]	0	191,244
Total Gross unrealized losses, held-to-maturity securities	[3]	0	1,303
Debt securities | Residential mortgage-backed securities
Gain (Loss) on Securities [Line Items]
Less than 12 months, Fair value, available-for-sale securities		9,567	9,524
Less than 12 months Gross unrealized losses, available-for-sale securities		41	62
12 months or more Fair value, available-for-sale securities		6,794	5,450
12 months or more Gross unrealized losses, available-for-sale securities		82	89
Total Fair value, available-for-sale securities		16,361	14,974
Total Gross unrealized losses, available-for-sale securities		123	151
Debt securities | Commercial mortgage-backed securities
Gain (Loss) on Securities [Line Items]
Less than 12 months, Fair value, available-for-sale securities		6,052	15,115
Less than 12 months Gross unrealized losses, available-for-sale securities		15	85
12 months or more Fair value, available-for-sale securities		11,396	7,478
12 months or more Gross unrealized losses, available-for-sale securities		54	21
Total Fair value, available-for-sale securities		17,448	22,593
Total Gross unrealized losses, available-for-sale securities		69	106
Debt securities | Japanese corporate bonds and other debt securities
Gain (Loss) on Securities [Line Items]
Less than 12 months, Fair value, available-for-sale securities		565,278	669,572
Less than 12 months Gross unrealized losses, available-for-sale securities		3,028	5,507
12 months or more Fair value, available-for-sale securities		597,714	608,361
12 months or more Gross unrealized losses, available-for-sale securities		5,757	3,265
Total Fair value, available-for-sale securities		1,162,992	1,277,933
Total Gross unrealized losses, available-for-sale securities	[4]	8,785	8,772
Debt securities | Foreign corporate bonds and other debt securities
Gain (Loss) on Securities [Line Items]
Less than 12 months, Fair value, available-for-sale securities		245,311	152,058
Less than 12 months Gross unrealized losses, available-for-sale securities		1,187	165
12 months or more Fair value, available-for-sale securities		2,712	5,564
12 months or more Gross unrealized losses, available-for-sale securities		3	3
Total Fair value, available-for-sale securities		248,023	157,622
Total Gross unrealized losses, available-for-sale securities	[5]	¥ 1,190	¥ 168
[1]	Agency mortgage-backed securities presented in this line consist of Japanese and Foreign agency mortgage-backed securities, of which the fair values were ¥40,417 million and ¥0 million, respectively, at March 31, 2020, and ¥0 million and ¥0 million, respectively, at September 30, 2020. 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 Ginnie Mae securities, which are guaranteed by the United States government.
[2]	Agency mortgage-backed securities presented in this line consist of Japanese and Foreign agency mortgage-backed securities, of which the fair values were ¥504,953 million and ¥61 million, respectively, at March 31, 2020, and ¥519,974 million and ¥51 million, respectively, at September 30, 2020. 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.
[3]	All Agency mortgage-backed securities presented in this line are Ginnie Mae securities.
[4]	Other debt securities presented in this line primarily consist of Japanese asset-backed securities (“ABS”), of which the total fair values was ¥139,888 million at September 30, 2020.
[5]	Other debt securities presented in this line primarily consist of Foreign negotiable certificates of deposit (“NCDs”) and ABS, of which the total fair values were ¥271,387 million at March 31, 2020, and ¥319,044 million at September 30, 2020.

Investments - Gross Unrealize_2

Investments - Gross Unrealized Losses and Fair Value of Available-for-Sale and Held-to-Maturity Securities, Aggregated by Length of Time that Individual Securities Have Been in a Continuous Unrealized Loss Position (Parenthetical) (Detail) - JPY (¥) ¥ in Millions		Sep. 30, 2020	Mar. 31, 2020
Gain (Loss) on Securities [Line Items]
Fair value, available-for-sale securities		¥ 13,204,017	¥ 12,530,189
Debt securities | Agency mortgage-backed securities
Gain (Loss) on Securities [Line Items]
Fair value, available-for-sale securities	[1]	40,747	40,417
Debt securities | Domestic Government Sponsored Enterprises Debt Securities [Member] | Agency mortgage-backed securities
Gain (Loss) on Securities [Line Items]
Fair value, available-for-sale securities		¥ 40,747	¥ 40,417
[1]	Agency mortgage-backed securities presented in this line consist of Japanese and Foreign agency mortgage-backed securities, of which the fair values were ¥40,417 million and ¥0 million, respectively, at March 31, 2020, and ¥0 million and ¥0 million, respectively, at September 30, 2020. 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 Ginnie Mae securities, which are guaranteed by the United States government.

Investments - Realized Gains an

Investments - Realized Gains and Losses on Sales of Available-for-Sale Securities (Detail) - JPY (¥) ¥ in Millions	6 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Debt Securities, Available-for-sale [Line Items]
Gross realized gains	¥ 5,101	¥ 36,183
Gross realized losses	(3,694)	(6,167)
Net realized gains (losses) on sales of available-for-sale securities	¥ 1,407	¥ 30,016

Investments - Summary of Detail

Investments - Summary of Details of Net Gains and Losses on Equity Securities (Detail) - JPY (¥) ¥ in Millions		6 Months Ended
		Sep. 30, 2020	Sep. 30, 2019
Gain (Loss) on Securities [Line Items]
Net gains (losses) recognized during the period on equity securities	[1]	¥ 266,119	¥ (126,648)
Less: Net gains (losses) recognized during the period on equity securities sold during the period		34,985	(3,084)
Unrealized gains (losses) recognized during the reporting period on equity securities still held at the reporting period		¥ 231,134	¥ (123,564)
[1]	These amounts are revenues from contracts that do not meet the scope of ASC 606.

Investments - Summary of Equity

Investments - Summary of Equity Securities Without Readily Determinable Fair Values (Detail) - JPY (¥) ¥ in Millions	Sep. 30, 2020	Mar. 31, 2020
Equity Securities without Readily Determinable Fair Value [Line Items]
Carrying amounts at the end of the period	¥ 402,194	¥ 419,775
Downward adjustments and impairments	3,800	2,435
Upward adjustments	¥ 9,104	¥ 9,128

Investments - Summary of Downwa

Investments - Summary of Downward Adjustments and Impairments and Upward Adjustments (Detail) - JPY (¥) ¥ in Millions	6 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Equity Securities without Readily Determinable Fair Value [Line Items]
Downward adjustments and impairments	¥ 1,411	¥ 430
Upward adjustments	¥ 34	¥ 6,527

Investments - Summary of Compos

Investments - Summary of Composition of Other Investments (Detail) - JPY (¥) ¥ in Millions	Sep. 30, 2020	Mar. 31, 2020
Schedule of Investments [Line Items]
Equity method investments	¥ 412,281	¥ 404,513
Investments held by consolidated investment companies	55,682	39,438
Total	¥ 467,963	¥ 443,951

Loans - Loans Outstanding by Do

Loans - Loans Outstanding by Domicile and Industry of Borrower (Detail) - JPY (¥) ¥ in Millions		Sep. 30, 2020	Mar. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		¥ 90,632,514	¥ 87,677,169
Less: Unearned income and deferred loan fees—net		156,767	149,081
Total loans before allowance for credit losses on loans		90,475,747	87,528,088
Domestic
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		59,594,397	56,030,511
Domestic | Manufacturing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		11,700,375	9,731,028
Domestic | Construction and real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		10,172,843	9,603,433
Domestic | Services
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		6,294,310	5,992,511
Domestic | Wholesale and retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		5,415,605	5,219,727
Domestic | Transportation and communications
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		3,978,708	3,832,884
Domestic | Banks and other financial institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		4,719,863	4,634,442
Domestic | Government and public institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		2,639,956	2,198,805
Domestic | Other industries
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[1]	5,517,220	5,389,347
Domestic | Mortgage loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		8,357,042	8,567,099
Domestic | Other individual loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		798,475	861,235
Foreign
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		31,038,117	31,646,658
Foreign | Banks and other financial institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		10,502,326	10,475,277
Foreign | Government and public institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		308,171	317,284
Foreign | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		20,190,048	20,818,709
Foreign | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		¥ 37,572	¥ 35,388
[1]	Other industries of domestic includes trade receivables and lease receivables of consolidated VIEs.

Loans - Additional Information

Loans - Additional Information (Detail) - JPY (¥) ¥ in Millions	6 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Mar. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net losses on sales of loans	¥ 1,178	¥ 179
Loans held for sale	22,404		¥ 60,084
Accrued Income [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrued interest receivables	82,321
Impaired Financing Receivables with No Related Allowance
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired loans partially charged off	¥ 32,783		¥ 20,378

Loans - Credit Quality Informat

Loans - Credit Quality Information of Loans Based on MHFG Group's Internal Rating System (Detail) - JPY (¥) ¥ in Millions	Sep. 30, 2020	Mar. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	¥ 90,632,514	¥ 87,677,169
Domestic
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	59,594,397	56,030,511
Foreign
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	31,038,117	31,646,658
Normal obligors | Domestic | Retail | Housing loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	437,780
2019	668,358
2018	627,669
2017	634,528
2016	783,929
Prior to 2016	4,879,204
Revolving loan	0
Total	8,031,468
Total		8,215,781
Normal obligors | Domestic | Retail | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	327,506
2019	209,899
2018	152,679
2017	106,359
2016	102,735
Prior to 2016	361,209
Revolving loan	523,640
Total	1,784,027
Total		1,783,779
Watch obligors | Domestic | Retail | Housing loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	560
2019	1,178
2018	1,827
2017	1,579
2016	2,217
Prior to 2016	43,397
Revolving loan	0
Total	50,758
Total		57,478
Watch obligors | Domestic | Retail | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	36,270
2019	17,587
2018	11,754
2017	6,911
2016	4,534
Prior to 2016	6,846
Revolving loan	12,185
Total	96,087
Total		81,463
Nonaccrual loans | Domestic | Retail | Housing loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	18,941
2019	6,528
2018	1,525
2017	1,432
2016	1,778
Prior to 2016	38,456
Revolving loan	0
Total	68,660
Total		57,696
Nonaccrual loans | Domestic | Retail | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	26,633
2019	6,905
2018	1,945
2017	1,000
2016	965
Prior to 2016	9,532
Revolving loan	11,567
Total	58,547
Total		59,782
Financing Receivables Not Impaired
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	24,824,517
2019	16,069,963
2018	13,270,550
2017	5,523,602
2016	4,710,392
Prior to 2016	11,263,389
Revolving loan	14,813,334
Total	90,475,747
Total		87,677,169
Financing Receivables Not Impaired | Domestic
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	13,582,965
2019	9,421,113
2018	9,327,773
2017	3,932,938
2016	3,869,379
Prior to 2016	9,465,007
Revolving loan	9,923,183
Total	59,522,358
Total		56,030,511
Financing Receivables Not Impaired | Foreign
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	11,241,552
2019	6,648,850
2018	3,942,777
2017	1,590,664
2016	841,013
Prior to 2016	1,798,382
Revolving loan	4,890,151
Total	30,953,389
Total		31,646,658
Financing Receivables Not Impaired | Normal obligors | Domestic | Soverign
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	1,907,424
2019	264,528
2018	126,868
2017	87,021
2016	92,664
Prior to 2016	485,721
Revolving loan	13,700
Total	2,977,926
Total		2,559,420
Financing Receivables Not Impaired | Normal obligors | Domestic | Financial institutions borrower
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	15,637
2019	155,415
2018	261,601
2017	26,841
2016	85,303
Prior to 2016	74,009
Revolving loan	187,102
Total	805,908
Total		790,659
Financing Receivables Not Impaired | Normal obligors | Domestic | Corporate | Large companies
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	9,754,935
2019	7,343,964
2018	7,517,546
2017	2,710,108
2016	2,498,507
Prior to 2016	2,978,989
Revolving loan	8,279,869
Total	41,083,918
Total		37,979,353
Financing Receivables Not Impaired | Normal obligors | Domestic | Corporate | Small and medium sized companies
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	381,487
2019	543,822
2018	456,363
2017	260,146
2016	232,638
Prior to 2016	485,430
Revolving loan	502,124
Total	2,862,010
Total		2,941,599
Financing Receivables Not Impaired | Normal obligors | Foreign | Soverign
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	91,542
2019	99,248
2018	32,403
2017	149,794
2016	5,907
Prior to 2016	90,988
Revolving loan	81,008
Total	550,890
Total		558,384
Financing Receivables Not Impaired | Normal obligors | Foreign | Financial institutions borrower
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	750,039
2019	654,755
2018	421,876
2017	95,375
2016	4,509
Prior to 2016	3,536
Revolving loan	49,997
Total	1,980,087
Total		2,008,516
Financing Receivables Not Impaired | Normal obligors | Foreign | Corporate
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	10,181,936
2019	5,813,342
2018	3,419,918
2017	1,298,791
2016	804,580
Prior to 2016	1,624,422
Revolving loan	4,630,806
Total	27,773,795
Total		28,555,991
Financing Receivables Not Impaired | Normal obligors | Foreign | Retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	3,613
2019	9,806
2018	6,008
2017	2,956
2016	1,517
Prior to 2016	2,527
Revolving loan	102
Total	26,529
Total		30,862
Financing Receivables Not Impaired | Watch obligors | Domestic | Soverign
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	2,859
2019	6,914
2018	2,951
2017	1,134
2016	257
Prior to 2016	34
Revolving loan	0
Total	14,149
Total		10,939
Financing Receivables Not Impaired | Watch obligors | Domestic | Financial institutions borrower
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior to 2016	0
Revolving loan	0
Total	0
Total		0
Financing Receivables Not Impaired | Watch obligors | Domestic | Corporate | Large companies
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	424,745
2019	92,446
2018	82,206
2017	56,363
2016	33,737
Prior to 2016	33,847
Revolving loan	196,544
Total	919,888
Total		840,289
Financing Receivables Not Impaired | Watch obligors | Domestic | Corporate | Small and medium sized companies
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	46,537
2019	32,174
2018	37,116
2017	13,321
2016	15,523
Prior to 2016	28,933
Revolving loan	30,521
Total	204,125
Total		189,075
Financing Receivables Not Impaired | Watch obligors | Foreign | Soverign
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior to 2016	20,124
Revolving loan	0
Total	20,124
Total		19,971
Financing Receivables Not Impaired | Watch obligors | Foreign | Financial institutions borrower
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	912
2019	152
2018	686
2017	0
2016	0
Prior to 2016	0
Revolving loan	0
Total	1,750
Total		78
Financing Receivables Not Impaired | Watch obligors | Foreign | Corporate
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	172,225
2019	43,785
2018	47,998
2017	37,862
2016	15,899
Prior to 2016	35,532
Revolving loan	84,646
Total	437,947
Total		336,470
Financing Receivables Not Impaired | Watch obligors | Foreign | Retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	174
2019	1,110
2018	647
2017	361
2016	109
Prior to 2016	11
Revolving loan	0
Total	2,412
Total		858
Financing Receivables Not Impaired | Nonaccrual loans | Domestic | Soverign
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior to 2016	0
Revolving loan	0
Total	0
Total		0
Financing Receivables Not Impaired | Nonaccrual loans | Domestic | Financial institutions borrower
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	167
2019	0
2018	180
2017	0
2016	0
Prior to 2016	0
Revolving loan	1,600
Total	1,947
Total		0
Financing Receivables Not Impaired | Nonaccrual loans | Domestic | Corporate | Large companies
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	142,730
2019	55,771
2018	41,249
2017	20,295
2016	11,956
Prior to 2016	29,551
Revolving loan	136,213
Total	437,765
Total		343,439
Financing Receivables Not Impaired | Nonaccrual loans | Domestic | Corporate | Small and medium sized companies
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	58,754
2019	15,624
2018	4,294
2017	5,900
2016	2,636
Prior to 2016	9,849
Revolving loan	28,118
Total	125,175
Total		119,759
Financing Receivables Not Impaired | Nonaccrual loans | Foreign | Soverign
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	0
2019	741
2018	0
2017	0
2016	0
Prior to 2016	0
Revolving loan	0
Total	741
Total		0
Financing Receivables Not Impaired | Nonaccrual loans | Foreign | Financial institutions borrower
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior to 2016	0
Revolving loan	0
Total	0
Total		0
Financing Receivables Not Impaired | Nonaccrual loans | Foreign | Corporate
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	41,085
2019	25,405
2018	12,954
2017	5,422
2016	8,448
Prior to 2016	21,241
Revolving loan	43,592
Total	158,147
Total		135,522
Financing Receivables Not Impaired | Nonaccrual loans | Foreign | Retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
2020	26
2019	506
2018	287
2017	103
2016	44
Prior to 2016	1
Revolving loan	0
Total	¥ 967
Total		¥ 6

Loans - Impaired Loans Informat

Loans - Impaired Loans Information (Detail) - JPY (¥) ¥ in Millions	6 Months Ended	12 Months Ended
	Sep. 30, 2020	Mar. 31, 2020
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual loans with an allowance	¥ 711,063	¥ 596,000
Nonaccrual loans without an allowance	140,886	120,204
Total nonaccrual loans	851,949	716,204
Interest income recognized	5,147	10,694
Domestic
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual loans with an allowance	600,768	500,711
Nonaccrual loans without an allowance	91,326	79,965
Total nonaccrual loans	692,094	580,676
Interest income recognized	4,189	7,662
Domestic | Retail | Housing loan
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual loans with an allowance	40,358	28,263
Nonaccrual loans without an allowance	28,302	29,433
Total nonaccrual loans	68,660	57,696
Interest income recognized	535	937
Domestic | Retail | Other
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual loans with an allowance	36,270	36,220
Nonaccrual loans without an allowance	22,277	23,562
Total nonaccrual loans	58,547	59,782
Interest income recognized	373	846
Domestic | Large companies | Corporate
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual loans with an allowance	416,637	333,442
Nonaccrual loans without an allowance	21,128	9,997
Total nonaccrual loans	437,765	343,439
Interest income recognized	2,501	4,155
Domestic | Small and medium sized companies | Corporate
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual loans with an allowance	105,556	102,786
Nonaccrual loans without an allowance	19,619	16,973
Total nonaccrual loans	125,175	119,759
Interest income recognized	777	1,724
Domestic | Banks and other financial institutions
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual loans with an allowance	1,947
Nonaccrual loans without an allowance	0
Total nonaccrual loans	1,947
Interest income recognized	3
Foreign
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual loans with an allowance	110,295	95,289
Nonaccrual loans without an allowance	49,560	40,239
Total nonaccrual loans	159,855	135,528
Interest income recognized	¥ 958	¥ 3,032

Loans - Troubled Debt Restructu

Loans - Troubled Debt Restructurings Entered Modified Periods by Type of Concession Granted (Detail) - JPY (¥) ¥ in Millions		6 Months Ended
		Sep. 30, 2020	Sep. 30, 2019
Financing Receivable, Modifications [Line Items]
Loan forgiveness or debt to equity swaps Recorded investment	[1]	¥ 0	¥ 1,159
Loan forgiveness or debt to equity swaps charge-offs		0	8,728
Interest rate reduction and/or postponement of principal and/or interest		426,021	257,573
Domestic
Financing Receivable, Modifications [Line Items]
Loan forgiveness or debt to equity swaps Recorded investment	[1]	0	689
Loan forgiveness or debt to equity swaps charge-offs		0	3,806
Interest rate reduction and/or postponement of principal and/or interest		345,132	218,927
Domestic | Housing loan | Retail
Financing Receivable, Modifications [Line Items]
Loan forgiveness or debt to equity swaps Recorded investment	[1]	0
Loan forgiveness or debt to equity swaps charge-offs		0
Interest rate reduction and/or postponement of principal and/or interest		14,690	3,742
Domestic | Other | Retail
Financing Receivable, Modifications [Line Items]
Loan forgiveness or debt to equity swaps Recorded investment	[1]	0
Loan forgiveness or debt to equity swaps charge-offs		0
Interest rate reduction and/or postponement of principal and/or interest		9,130	7,468
Domestic | Large companies | Corporate
Financing Receivable, Modifications [Line Items]
Loan forgiveness or debt to equity swaps Recorded investment	[1]	0	689
Loan forgiveness or debt to equity swaps charge-offs		0	3,806
Interest rate reduction and/or postponement of principal and/or interest		264,952	152,373
Domestic | Small and medium sized companies | Corporate
Financing Receivable, Modifications [Line Items]
Loan forgiveness or debt to equity swaps Recorded investment	[1]	0
Loan forgiveness or debt to equity swaps charge-offs		0
Interest rate reduction and/or postponement of principal and/or interest		54,760	55,344
Domestic | Banks and other financial institutions
Financing Receivable, Modifications [Line Items]
Loan forgiveness or debt to equity swaps Recorded investment	[1]	0
Loan forgiveness or debt to equity swaps charge-offs		0
Interest rate reduction and/or postponement of principal and/or interest		1,600
Foreign
Financing Receivable, Modifications [Line Items]
Loan forgiveness or debt to equity swaps Recorded investment	[1]	0	470
Loan forgiveness or debt to equity swaps charge-offs		0	4,922
Interest rate reduction and/or postponement of principal and/or interest		¥ 80,889	¥ 38,646
[1]	Amounts represent the book values of loans immediately after the restructurings.

Loans - Payment Defaults Occurr

Loans - Payment Defaults Occurred During Periods with Respect to Loans Modified as Troubled Debt Restructurings within Previous Six Months (Detail) - JPY (¥) ¥ in Millions	6 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Financing Receivable, Modifications [Line Items]
Recorded investment	¥ 51,340	¥ 16,790
Housing loan
Financing Receivable, Modifications [Line Items]
Recorded investment	505	686
Other
Financing Receivable, Modifications [Line Items]
Recorded investment	1,104	1,349
Domestic
Financing Receivable, Modifications [Line Items]
Recorded investment	7,554	10,354
Domestic | Corporate | Large companies
Financing Receivable, Modifications [Line Items]
Recorded investment	2,084	5,875
Domestic | Corporate | Small and medium sized companies
Financing Receivable, Modifications [Line Items]
Recorded investment	3,861	2,444
Foreign
Financing Receivable, Modifications [Line Items]
Recorded investment	¥ 43,786	¥ 6,436

Loans - Age Analysis of Past Du

Loans - Age Analysis of Past Due Loans (Detail) - JPY (¥) ¥ in Millions	6 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Mar. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	¥ 51,340	¥ 16,790
Housing loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	505	686
Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	1,104	1,349
Domestic
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	7,554	10,354
Domestic | Corporate | Large companies
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	2,084	5,875
Domestic | Corporate | Small and medium sized companies
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	3,861	2,444
Foreign
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	43,786	¥ 6,436
30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	24,781		¥ 27,589
30-59 Days Past Due | Soverign
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	0
30-59 Days Past Due | Domestic
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	22,955		26,375
30-59 Days Past Due | Domestic | Corporate | Large companies
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	311		2,146
30-59 Days Past Due | Domestic | Corporate | Small and medium sized companies
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	2,093		2,347
30-59 Days Past Due | Domestic | Retail | Housing loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	15,831		15,703
30-59 Days Past Due | Domestic | Retail | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	4,720		6,179
30-59 Days Past Due | Domestic | Banks and other financial institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	0
30-59 Days Past Due | Foreign
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	1,826		1,214
60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	10,815		15,179
60-89 Days Past Due | Soverign
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	0
60-89 Days Past Due | Domestic
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	10,179		14,998
60-89 Days Past Due | Domestic | Corporate | Large companies
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	269		2,013
60-89 Days Past Due | Domestic | Corporate | Small and medium sized companies
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	604		894
60-89 Days Past Due | Domestic | Retail | Housing loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	7,870		10,078
60-89 Days Past Due | Domestic | Retail | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	1,436		2,013
60-89 Days Past Due | Domestic | Banks and other financial institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	0
60-89 Days Past Due | Foreign
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	636		181
90 Days or More Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	150,703		118,202
90 Days or More Past Due | Soverign
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	0
90 Days or More Past Due | Domestic
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	90,168		89,480
90 Days or More Past Due | Domestic | Corporate | Large companies
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	38,868		38,364
90 Days or More Past Due | Domestic | Corporate | Small and medium sized companies
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	11,226		9,187
90 Days or More Past Due | Domestic | Retail | Housing loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	25,922		26,690
90 Days or More Past Due | Domestic | Retail | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	14,152		15,239
90 Days or More Past Due | Domestic | Banks and other financial institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	0
90 Days or More Past Due | Foreign
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	60,535		28,722
Total past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	186,299		160,970
Total past due | Domestic
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	123,302		130,853
Total past due | Domestic | Soverign
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	0
Total past due | Domestic | Corporate | Large companies
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	39,448		42,523
Total past due | Domestic | Corporate | Small and medium sized companies
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	13,923		12,428
Total past due | Domestic | Retail | Housing loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	49,623		52,471
Total past due | Domestic | Retail | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	20,308		23,431
Total past due | Domestic | Banks and other financial institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	0
Total past due | Foreign
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	62,997		30,117
Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	90,289,448		87,516,199
Current | Domestic
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	59,399,056		55,899,658
Current | Domestic | Soverign
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	2,992,075		2,570,359
Current | Domestic | Corporate | Large companies
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	42,402,123		39,120,558
Current | Domestic | Corporate | Small and medium sized companies
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	3,177,387		3,238,005
Current | Domestic | Retail | Housing loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	8,101,263		8,278,484
Current | Domestic | Retail | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	1,918,353		1,901,593
Current | Domestic | Banks and other financial institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	807,855		790,659
Current | Foreign
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	30,890,392		31,616,541
Total
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	90,475,747		87,677,169
Total | Domestic
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	59,522,358		56,030,511
Total | Domestic | Soverign
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	2,992,075		2,570,359
Total | Domestic | Corporate | Large companies
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	42,441,571		39,163,081
Total | Domestic | Corporate | Small and medium sized companies
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	3,191,310		3,250,433
Total | Domestic | Retail | Housing loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	8,150,886		8,330,955
Total | Domestic | Retail | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	1,938,661		1,925,024
Total | Domestic | Banks and other financial institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	807,855		790,659
Total | Foreign
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	¥ 30,953,389		¥ 31,646,658

Allowance for Credit Losses o_3

Allowance for Credit Losses on Loans (Changes in Allowance for Credit Losses On Loan and Loans Outstanding Disaggregated on Basis of Impairment Method, by Portfolio Segment) (Detail) - JPY (¥) ¥ in Millions		6 Months Ended
		Sep. 30, 2020	Sep. 30, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at beginning of period		¥ 440,855	¥ 307,201
Provision (credit) for credit losses on loans		53,082	13,773
Charge-offs		(31,863)	(29,034)
Recoveries		5,739	4,054
Net charge-offs		(26,124)	(24,980)
Others	[1]	(1,042)	(4,572)
Balance at end of fiscal year		622,526	291,422
Cumulative effect of change in accounting principles
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at beginning of period		155,755
Cumulative effect, period of adoption, adjusted balance
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at beginning of period		596,610
Corporate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at beginning of period		413,026	277,955
Provision (credit) for credit losses on loans		64,133	12,268
Charge-offs		(28,417)	(25,147)
Recoveries		5,260	2,785
Net charge-offs		(23,157)	(22,362)
Others	[1]	(997)	(4,570)
Balance at end of fiscal year		530,519	263,291
Corporate | Cumulative effect of change in accounting principles
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at beginning of period		77,514
Corporate | Cumulative effect, period of adoption, adjusted balance
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at beginning of period		490,540
Retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at beginning of period		27,829	29,246
Provision (credit) for credit losses on loans		(11,051)	1,505
Charge-offs		(3,446)	(3,887)
Recoveries		479	1,269
Net charge-offs		(2,967)	(2,618)
Others	[1]	(45)	(2)
Balance at end of fiscal year		92,007	¥ 28,131
Retail | Cumulative effect of change in accounting principles
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at beginning of period		78,241
Retail | Cumulative effect, period of adoption, adjusted balance
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at beginning of period		¥ 106,070
[1]	Others includes primarily foreign exchange translation.

Other Assets and Liabilities (D

Other Assets and Liabilities (Details of Other Assets and Liabilities) (Detail) - JPY (¥) ¥ in Millions		Sep. 30, 2020	Mar. 31, 2020
Other assets:
Receivables from brokers, dealers and customers for securities transactions		¥ 898,924	¥ 783,439
Other		416,064	358,702
Collateral pledged for derivative transactions		1,079,050	1,246,026
Margins provided for futures contracts		316,791	602,039
Other		909,155	941,167
Prepaid pension cost		986,767	711,981
Right-of-use assets		586,365	613,068
Security deposits		108,204	107,294
Loans held for sale		22,404	60,084
Other		540,514	542,079
Total		5,864,238	5,965,879
Other liabilities:
Payables to brokers, dealers and customers for securities transactions		2,065,408	2,161,075
Other		365,446	375,127
Guaranteed trust principal	[1]	808,172	824,431
Lease liabilities		¥ 600,087	627,250
Operating Lease, Liability, Statement of Financial Position [Extensible List]		us-gaap:OperatingLeaseLiability
Collateral accepted for derivative transactions		¥ 587,426	846,426
Margins accepted for futures contracts		558,138	797,317
Unearned income		120,352	122,072
Other		1,194,591	1,244,697
Total		¥ 6,299,620	¥ 6,998,395
[1]	Guaranteed trust principal, included in All other liabilities in the disclosure about consolidated VIEs in the accompanying balance sheets, is a liability of certain consolidated trust arrangements that meet the definition of a VIE for which the MHFG Group provides guarantees for the repayment of principal. See Note 15 “Variable interest entities and securitizations” for further discussion of the guaranteed principal money trusts.

Preferred and Common Stock (Com

Preferred and Common Stock (Composition of Preferred Stock) (Detail) - shares	Sep. 30, 2020	Mar. 31, 2020
Class Fourteen Preferred Stock
Class of Stock [Line Items]
Number of shares Authorized	90,000,000	90,000,000
Number of shares Issued	0	0
Class Fifteen Preferred Stock
Class of Stock [Line Items]
Number of shares Authorized	90,000,000	90,000,000
Number of shares Issued	0	0
Class Sixteen Preferred Stock
Class of Stock [Line Items]
Number of shares Authorized	150,000,000	150,000,000
Number of shares Issued	0	0

Preferred and Common Stock - Ad

Preferred and Common Stock - Additional Information (Detail) - shares	Sep. 30, 2020	Mar. 31, 2020
Class of Stock [Line Items]
Common Stock, Shares, Issued	2,539,249,894	2,539,249,894

Accumulated other comprehensi_3

Accumulated other comprehensive income (loss), net of tax (Changes in Each Component of AOCI) (Detail) - JPY (¥) ¥ in Millions		6 Months Ended
		Sep. 30, 2020	Sep. 30, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period		¥ 9,175,624
Less: reclassification adjustments for losses (gains) included in net income		(1,819)
Change during period		142,550	¥ (56,583)
Balance at end of fiscal year		9,140,053	9,486,573
Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period		(9,494)	164,021
Change during period		143,331	(56,254)
Balance at end of fiscal year		133,837	106,715
Accumulated Other Comprehensive Income | Cumulative effect of change in accounting principles
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period		0	(1,052)	[1]
Accumulated Other Comprehensive Income | Cumulative effect, period of adoption, adjusted balance
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period		(9,494)	162,969
Net unrealized gains (losses) on available-for-sale securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period		(19,592)	22,019
Unrealized gains (losses) during period		644	25,843
Less: reclassification adjustments for losses (gains) included in net income		754	(20,824)
Change during period		1,398	5,019
Balance at end of fiscal year		(18,194)	27,038
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period		(109,872)	(58,558)
Foreign currency translation adjustments during period		(36,652)	(63,466)
Less: reclassification adjustments for losses (gains) included in net income		(409)
Change during period		(37,061)	(63,466)
Balance at end of fiscal year		(146,933)	(123,076)
Foreign currency translation adjustments | Cumulative effect of change in accounting principles
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	[1]		(1,052)
Foreign currency translation adjustments | Cumulative effect, period of adoption, adjusted balance
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period		(109,872)	(59,610)
Pension liability adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period		69,455	196,446
Unrealized gains (losses) during period		190,394	(1,720)
Less: reclassification adjustments for losses (gains) included in net income		672	(2,130)
Change during period		191,066	(3,850)
Balance at end of fiscal year		260,521	192,596
Accumulated Own Credit Risk Adjustment Including Portion Attributable to Noncontrolling Interest
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period		50,515	4,114
Unrealized gains (losses) during period		(9,340)	7,320
Less: reclassification adjustments for losses (gains) included in net income		(2,732)	(1,277)
Change during period		(12,072)	6,043
Balance at end of fiscal year		¥ 38,443	¥ 10,157
[1]	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.

Accumulated other comprehensi_4

Accumulated other comprehensive income (loss), net of tax (Amounts Reclassified Out of Accumulated Other Comprehensive Income into Net Income) (Detail) ¥ in Millions	6 Months Ended
	Sep. 30, 2020JPY (¥)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Before tax	¥ 2,451	[1]
Tax effect	(632)	[2]
Net of tax before allocation to noncontrolling interests	1,819
Net of tax attributable to noncontrolling interests	(104)	[2]
Net of tax attributable to MHFG shareholders	1,715
Accumulated Net Unrealized Investment Gain (Loss) | Gain (Loss) on Investments
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Before tax	(1,065)	[1]
Tax effect	306	[2]
Net of tax before allocation to noncontrolling interests	(759)
Net of tax attributable to noncontrolling interests	5	[2]
Net of tax attributable to MHFG shareholders	(754)
Accumulated Defined Benefit Plans Adjustment | Salaries and employee benefits
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Before tax	(1,004)	[1]
Tax effect	321	[2]
Net of tax before allocation to noncontrolling interests	(683)
Net of tax attributable to noncontrolling interests	11	[2]
Net of tax attributable to MHFG shareholders	(672)
Accumulated Own Credit Risk Adjustment | Other Noninterest Income (Expenses)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Before tax	4,111	[1]
Tax effect	(1,259)	[2]
Net of tax before allocation to noncontrolling interests	2,852
Net of tax attributable to noncontrolling interests	(120)	[2]
Net of tax attributable to MHFG shareholders	2,732
Accumulated Foreign Currency Adjustment Including Portion Attributable to Noncontrolling Interest [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net of tax before allocation to noncontrolling interests	409
Accumulated Foreign Currency Adjustment Including Portion Attributable to Noncontrolling Interest [Member] | Foreign exchange gains (losses)-net
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Before tax	409	[1]
Net of tax before allocation to noncontrolling interests	409
Net of tax attributable to MHFG shareholders	¥ 409
[1]	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.
[2]	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.

Regulatory Matters (Capital Ade

Regulatory Matters (Capital Adequacy Ratios of MHFG, MHBK, and MHTB Calculated in Accordance with Japanese GAAP and Guidelines Established by Financial Services Agency) (Detail) - JPY (¥) ¥ in Billions		Sep. 30, 2020		Mar. 31, 2020
Mizuho Financial Group Inc | Consolidated
Common Equity Tier 1 capital:
Required	[1]	¥ 5,159		¥ 4,978
Actual		7,453		7,245
Required	[1]	6,125		5,910
Actual		¥ 9,468		¥ 9,024
Required	[1]	9.51%		9.51%
Actual		14.69%		14.52%
Required	[1]	¥ 7,413		¥ 7,152
Actual		¥ 11,133		¥ 10,722
Required	[1]	11.51%		11.51%
Actual		17.28%		17.25%
Required		¥ 5,874	[2]	¥ 6,629
Actual		¥ 9,468	[2]	¥ 9,024
Common Equity Tier 1 capital:
Required	[1]	8.01%		8.01%
Actual		11.57%		11.65%
Leverage Ratio:
Required		3.00%		3.00%
Actual		4.83%		4.08%
Mizuho Bank Limited | Consolidated
Common Equity Tier 1 capital:
Required		¥ 2,689		¥ 2,567
Actual		6,756		6,501
Required		3,585		3,422
Actual		¥ 8,765		¥ 8,275
Required		6.00%		6.00%
Actual		14.66%		14.50%
Required		¥ 4,780		¥ 4,563
Actual		¥ 10,338		¥ 9,865
Required		8.00%		8.00%
Actual		17.30%		17.29%
Required		¥ 5,450	[2]	¥ 6,160
Actual		¥ 8,765	[2]	¥ 8,275
Common Equity Tier 1 capital:
Required		4.50%		4.50%
Actual		11.30%		11.39%
Leverage Ratio:
Required		3.00%		3.00%
Actual		4.82%		4.02%
Mizuho Bank Limited | Non-consolidated
Common Equity Tier 1 capital:
Required		¥ 2,525		¥ 2,403
Actual		6,369		6,130
Required		3,367		3,204
Actual		¥ 8,381		¥ 7,905
Required		6.00%		6.00%
Actual		14.93%		14.80%
Required		¥ 4,489		¥ 4,272
Actual		¥ 9,943		¥ 9,482
Required		8.00%		8.00%
Actual		17.71%		17.75%
Required		¥ 5,178	[2]	¥ 5,884
Actual		¥ 8,381	[2]	¥ 7,905
Common Equity Tier 1 capital:
Required		4.50%		4.50%
Actual		11.34%		11.47%
Leverage Ratio:
Required		3.00%		3.00%
Actual		4.85%		4.03%
Mizuho Trust & Banking Company Limited | Consolidated
Common Equity Tier 1 capital:
Required		¥ 87		¥ 93
Actual		509		489
Required		116		124
Actual		¥ 509		¥ 489
Required		6.00%		6.00%
Actual		26.24%		23.66%
Required		¥ 155		¥ 165
Actual		¥ 510		¥ 491
Required		8.00%		8.00%
Actual		26.27%		23.74%
Required		¥ 156	[2]	¥ 216
Actual		¥ 509	[2]	¥ 489
Common Equity Tier 1 capital:
Required		4.50%		4.50%
Actual		26.24%		23.64%
Leverage Ratio:
Required		3.00%		3.00%
Actual		9.79%		6.79%
Mizuho Trust & Banking Company Limited | Non-consolidated
Common Equity Tier 1 capital:
Required		¥ 87		¥ 93
Actual		494		475
Required		116		123
Actual		¥ 494		¥ 475
Required		6.00%		6.00%
Actual		25.49%		23.10%
Required		¥ 155		¥ 165
Actual		¥ 494		¥ 477
Required		8.00%		8.00%
Actual		25.52%		23.18%
Required		¥ 153	[2]	¥ 214
Actual		¥ 494	[2]	¥ 475
Common Equity Tier 1 capital:
Required		4.50%		4.50%
Actual		25.49%		23.10%
Leverage Ratio:
Required		3.00%		3.00%
Actual		9.66%		6.66%
[1]	The required ratios disclosed above, at March 31, 2020 and September 30, 2020, include the capital conservation buffer of 2.5%, the countercyclical capital buffer of 0.01%, and the additional loss absorbency requirements for global systemically important banks (“G-SIBs”) and domestic systemically important banks (“D-SIBs”) of 1.0%, which are all in addition to the regulatory minima. The respective required amounts are determined by applying the ratios to the sum of the risk weighted assets and certain other risk amounts.
[2]	The required and actual amounts disclosed above at September 30, 2020 exclude amounts of deposits to the Bank of Japan.

Regulatory Matters (Capital A_2

Regulatory Matters (Capital Adequacy Ratios of MHFG, MHBK, and MHTB Calculated in Accordance with Japanese GAAP and Guidelines Established by Financial Services Agency) (Parenthetical) (Detail)	6 Months Ended	12 Months Ended
	Sep. 30, 2020	Mar. 31, 2020
Japan Gaap Schedule Of Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]
Capital conservation buffer	2.50%	2.50%
Additional loss absorbency requirements for G-SIBs and D-SIBs	1.00%	1.00%
Countercyclical capital buffer	0.01%	0.01%

Earnings Per Common Share (Comp

Earnings Per Common Share (Computation of Basic and Diluted Earnings Per Common Share) (Detail) - JPY (¥) ¥ / shares in Units, shares in Thousands, ¥ in Millions		6 Months Ended
		Sep. 30, 2020	Sep. 30, 2019
Net income:
Net income attributable to MHFG common shareholders		¥ 315,886	¥ 212,984
Effect of dilutive securities
Net income attributable to common shareholders after assumed conversions		¥ 315,886	¥ 212,984
Shares:
Weighted average common shares outstanding		2,537,272	2,536,800
Effect of dilutive securities:
Stock options and the common shares of MHFG under the stock compensation programs	[1]	93	209
Weighted average common shares after assumed conversions		2,537,365	2,537,009
Earnings per common share:
Basic net income per common share		¥ 124.50	¥ 83.96
Diluted net income per common share	[1]	¥ 124.49	¥ 83.95
[1]	For the six months ended September 30, 2020, 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.

Income Taxes (Components of Inc

Income Taxes (Components of Income Tax Expense) (Detail) - JPY (¥) ¥ in Millions	6 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Reconciliation of Provision of Income Taxes [Line Items]
Current tax expense	¥ 79,954	¥ 88,437
Deferred tax expense (benefit)	57,807	(5,317)
Total income tax expense	¥ 137,761	¥ 83,120

Income Taxes (Detailed Amounts

Income Taxes (Detailed Amounts of Tax Effects of Items Recorded Directly in Equity) (Detail) - JPY (¥) ¥ in Millions	6 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Net unrealized gains (losses) on available-for-sale securities:
Unrealized gains (losses)	¥ 579	¥ 11,023
Less: reclassification adjustments	306	(9,192)
Total	885	1,831
Pension liability adjustments:
Unrealized gains (losses)	83,994	(643)
Less: reclassification adjustments	321	(937)
Total	84,315	(1,580)
Own credit risk adjustments:
Unrealized gains (losses)	(2,351)	(43)
Less: reclassification adjustments	(1,259)	(588)
Total	(3,610)	(631)
Total tax effect before allocation to noncontrolling interests	¥ 81,590	¥ (380)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - JPY (¥) ¥ in Millions	6 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Income Taxes [Line Items]
Statutory tax rate	30.62%	30.62%
Effective tax rate	25.15%	26.77%
Net operating loss carryforwards	¥ 623,000
Unrecognized Tax Benefits	¥ 4,382

Pension and Other Employee Be_3

Pension and Other Employee Benefit Plans (Components of Net Periodic Costs of Severance Indemnities and Pension Plans) (Detail) - JPY (¥) ¥ in Millions	6 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Defined Benefit Plan Disclosure [Line Items]
Service cost-benefits earned during the period	¥ 22,695	¥ 22,729
Interest costs on projected benefit obligations	2,931	2,666
Expected return on plan assets	(20,073)	(20,158)
Amortization of prior service cost (benefits)	205	19
Amortization of net actuarial loss (gain)	836	(3,064)
Special termination benefits	4,981	2,188
Net periodic benefit cost	¥ 11,575	¥ 4,380

Pension and Other Employee Be_4

Pension and Other Employee Benefit Plans - Additional Information (Detail) - JPY (¥) ¥ in Millions	6 Months Ended
	Sep. 30, 2020	Mar. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Pension plan, contribution expected to be paid during the next fiscal year		¥ 41,000
Total payment to pension plans	¥ 25,000
Additional contribution expected to be paid during remainder of fiscal year	16,000
Defined benefit plans, prior service costs recognised	¥ 73,998
Defined contribution plans effective date	Oct. 1, 2020

Derivative Financial Instrume_3

Derivative Financial Instruments (Summary of Notional and Fair Value Amounts of Derivative Instruments Outstanding) (Detail) - JPY (¥) ¥ in Billions		Sep. 30, 2020	Mar. 31, 2020
Derivatives, Fair Value [Line Items]
Notional amount	[1]	¥ 1,274,978	¥ 1,320,665
Interest rate contracts
Derivatives, Fair Value [Line Items]
Notional amount	[1]	1,084,971	1,123,546
Foreign exchange contracts
Derivatives, Fair Value [Line Items]
Notional amount	[1]	174,856	185,359
Equity-related contracts
Derivatives, Fair Value [Line Items]
Notional amount	[1]	7,012	6,684
Credit-related contracts
Derivatives, Fair Value [Line Items]
Notional amount	[1]	7,742	4,676
Other contracts
Derivatives, Fair Value [Line Items]
Notional amount	[1]	397	400
Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Fair value of derivative receivables	[2]	8,758	10,536
Fair value of derivative payables	[2]	8,251	10,021
Not Designated as Hedging Instrument | Interest rate contracts
Derivatives, Fair Value [Line Items]
Fair value of derivative receivables	[2]	6,135	7,232
Fair value of derivative payables	[2]	5,728	6,788
Not Designated as Hedging Instrument | Foreign exchange contracts
Derivatives, Fair Value [Line Items]
Fair value of derivative receivables	[2]	2,143	2,926
Fair value of derivative payables	[2]	2,160	2,899
Not Designated as Hedging Instrument | Equity-related contracts
Derivatives, Fair Value [Line Items]
Fair value of derivative receivables	[2]	397	310
Fair value of derivative payables	[2]	260	266
Not Designated as Hedging Instrument | Credit-related contracts
Derivatives, Fair Value [Line Items]
Fair value of derivative receivables	[2]	55	30
Fair value of derivative payables	[2]	77	29
Not Designated as Hedging Instrument | Other contracts
Derivatives, Fair Value [Line Items]
Fair value of derivative receivables	[2]	28	38
Fair value of derivative payables	[2]	¥ 26	¥ 39
[1]	Notional amount includes the sum of gross long and gross short third-party contracts.
[2]	Derivative receivables and payables are recorded in Trading account assets and Trading account liabilities, respectively.

Derivative Financial Instrume_4

Derivative Financial Instruments - Additional Information (Detail) - JPY (¥) ¥ in Millions	Sep. 30, 2020	Mar. 31, 2020
Derivative [Line Items]
Cash collateral provided and not offset against derivative positions and included in Other assets	¥ 1,079,050	¥ 1,246,026
Cash collateral accepted and not offset against derivative positions and included in Other liabilities	¥ 587,426	¥ 846,426

Derivative Financial Instrume_5

Derivative Financial Instruments (Summary of Gains and Losses Information Related to Net Investment Hedges) (Detail) - JPY (¥) ¥ in Millions	6 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recorded in OCI	¥ 1,538	¥ (1,044)
Financial instruments hedging foreign exchange risk
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recorded in OCI	¥ 1,538	¥ (1,044)

Derivative Financial Instrume_6

Derivative Financial Instruments (Summary of Gains and Losses Information Related to Net Investment Hedges) (Parenthetical) (Detail) - JPY (¥) ¥ in Millions	Sep. 30, 2020	Sep. 30, 2019
Financial instruments hedging foreign exchange risk
Derivative Instruments, Gain (Loss) [Line Items]
Accumulated other comprehensive income reclassified to earnings	¥ (1,312)	¥ (260)

Derivative Financial Instrume_7

Derivative Financial Instruments (Summary of Gains and Losses on Derivatives not Designated or Qualifying as Hedges) (Detail) - JPY (¥) ¥ in Millions		6 Months Ended
		Sep. 30, 2020	Sep. 30, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recorded in income		¥ 24,542	¥ 174,483
Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recorded in income		32,791	210,909
Foreign exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recorded in income		26,277	(30,736)
Equity-related contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recorded in income	[1]	(31,999)	(494)
Credit-related contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recorded in income	[2]	(29,219)	(3,546)
Other contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recorded in income		¥ 26,692	¥ (1,650)
[1]	The net gains (losses) excluded from the assessment of the effectiveness of fair value hedges is not included in the above table.
[2]	Amounts include the net gains (losses) of ¥(426) million and ¥(1,221) million on the credit derivatives economically managing the credit risk of loans during the six months ended September 30, 2019 and 2020, respectively.

Derivative Financial Instrume_8

Derivative Financial Instruments (Summary of Gains and Losses on Derivatives not Designated or Qualifying as Hedges) (Parenthetical) (Detail) - JPY (¥) ¥ in Millions		6 Months Ended
		Sep. 30, 2020	Sep. 30, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recorded in income		¥ 24,542	¥ 174,483
Credit-related contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recorded in income	[1]	(29,219)	(3,546)
Credit-related contracts | Loans related to credit derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recorded in income		¥ (1,221)	¥ (426)
[1]	Amounts include the net gains (losses) of ¥(426) million and ¥(1,221) million on the credit derivatives economically managing the credit risk of loans during the six months ended September 30, 2019 and 2020, respectively.

Derivative Financial Instrume_9

Derivative Financial Instruments (Summary of Notional and Fair Value Amounts of Credit Derivatives) (Detail) - JPY (¥) ¥ in Billions	Sep. 30, 2020	Mar. 31, 2020
Credit protection written
Credit Derivatives [Line Items]
Notional amount	¥ 3,217	¥ 1,816
Fair value	45	(5)
Credit protection written | Investment grade
Credit Derivatives [Line Items]
Notional amount	2,687	1,400
Fair value	37	(5)
Credit protection written | Non-investment grade
Credit Derivatives [Line Items]
Notional amount	530	416
Fair value	8
Credit protection purchased
Credit Derivatives [Line Items]
Notional amount	4,693	3,028
Fair value	¥ (67)	¥ 6

Derivative Financial Instrum_10

Derivative Financial Instruments (Maximum Potential Amount of Future Payments for Credit Protection Written by Expiration Period) (Detail) - JPY (¥) ¥ in Billions	Sep. 30, 2020	Mar. 31, 2020
Credit Derivatives [Line Items]
Maximum payout/Notional amount	¥ 3,217	¥ 1,816
One year or less
Credit Derivatives [Line Items]
Maximum payout/Notional amount	233	270
After one year through five years
Credit Derivatives [Line Items]
Maximum payout/Notional amount	2,793	1,368
After five years
Credit Derivatives [Line Items]
Maximum payout/Notional amount	¥ 191	¥ 178

Derivative Financial Instrum_11

Derivative Financial Instruments (Quantitative Information about Derivative Instruments with Credit-risk-related Contingent Features) (Detail) - JPY (¥) ¥ in Billions	Sep. 30, 2020	Mar. 31, 2020
Credit Derivatives [Line Items]
Aggregate fair value of derivative instruments with credit-risk-related contingent features in net liability positions	¥ 747	¥ 888
Collateral provided to counterparties in the normal course of business	703	818
Amount required to be posted as collateral or settled immediately if credit-risk-related contingent features were triggered	¥ 44	¥ 70

Commitments and Contingencies_2

Commitments and Contingencies (Summary of Maximum Potential Amount of Future Payments under Guarantees) (Detail) - JPY (¥) ¥ in Billions	Sep. 30, 2020	Mar. 31, 2020
Performance guarantees
Guarantor Obligations [Line Items]
Maximum potential/Contractual or Notional amount	¥ 2,527	¥ 2,456
Guarantees on loans
Guarantor Obligations [Line Items]
Maximum potential/Contractual or Notional amount	266	301
Guarantees on securities
Guarantor Obligations [Line Items]
Maximum potential/Contractual or Notional amount	96	110
Other guarantees
Guarantor Obligations [Line Items]
Maximum potential/Contractual or Notional amount	2,306	2,314
Guarantees for repayment of trust principal
Guarantor Obligations [Line Items]
Maximum potential/Contractual or Notional amount	31	59
Liabilities of trust accounts
Guarantor Obligations [Line Items]
Maximum potential/Contractual or Notional amount	456	446
Derivative financial instruments
Guarantor Obligations [Line Items]
Maximum potential/Contractual or Notional amount	¥ 21,097	¥ 21,756

Commitments and Contingencies_3

Commitments and Contingencies (Summary of Maximum Potential Amount of Future Payments of Certain Guarantees Classified Based on Internal Ratings) (Detail) - Performance guarantees, Guarantees on loans, Guarantees on securities and Other guarantees - JPY (¥) ¥ in Billions	Sep. 30, 2020	Mar. 31, 2020
Guarantor Obligations [Line Items]
Maximum potential/Contractual or Notional amount	¥ 5,195	¥ 5,181
Investment grade
Guarantor Obligations [Line Items]
Maximum potential/Contractual or Notional amount	4,079	4,233
Non-investment grade
Guarantor Obligations [Line Items]
Maximum potential/Contractual or Notional amount	¥ 1,116	¥ 948

Commitments and Contingencies_4

Commitments and Contingencies (Summary of Contractual Amounts with Regard to Undrawn Commitments) (Detail) - JPY (¥) ¥ in Billions		Sep. 30, 2020	Mar. 31, 2020
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Off-balance-sheet instruments, contractual amounts of the undrawn commitments		¥ 86,896	¥ 77,323
Commitments to Extend Credit
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Off-balance-sheet instruments, contractual amounts of the undrawn commitments	[1]	86,359	76,633
Commercial letters of credit
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Off-balance-sheet instruments, contractual amounts of the undrawn commitments		¥ 537	¥ 690
[1]	Commitments to extend credit include commitments to invest in securities.

Variable Interest Entities an_3

Variable Interest Entities and Securitizations (Consolidated Assets of Consolidated VIEs as well as Total Assets and Maximum Exposure to Loss for Significant Unconsolidated VIEs) (Detail) - JPY (¥) ¥ in Millions	Sep. 30, 2020	Mar. 31, 2020
Variable Interest Entity [Line Items]
Consolidated VIEs- Consolidated assets	¥ 217,594,620	¥ 211,218,760
Significant unconsolidated VIEs- Maximum exposure to loss	491,000	521,000
Consolidated VIEs
Variable Interest Entity [Line Items]
Consolidated VIEs- Consolidated assets	11,035,019	5,815,146
Unconsolidated VIEs
Variable Interest Entity [Line Items]
Consolidated VIEs- Consolidated assets	2,423,000	2,376,000
Asset-backed commercial paper/loan programs | Consolidated VIEs
Variable Interest Entity [Line Items]
Consolidated VIEs- Consolidated assets	2,045,000	2,160,000
Asset-backed securitizations
Variable Interest Entity [Line Items]
Significant unconsolidated VIEs- Maximum exposure to loss	8,000	7,000
Asset-backed securitizations | Consolidated VIEs
Variable Interest Entity [Line Items]
Consolidated VIEs- Consolidated assets	780,000	572,000
Asset-backed securitizations | Unconsolidated VIEs
Variable Interest Entity [Line Items]
Consolidated VIEs- Consolidated assets	77,000	77,000
Investments in securitization products | Consolidated VIEs
Variable Interest Entity [Line Items]
Consolidated VIEs- Consolidated assets	370,000	370,000
Investment funds
Variable Interest Entity [Line Items]
Significant unconsolidated VIEs- Maximum exposure to loss	483,000	514,000
Investment funds | Consolidated VIEs
Variable Interest Entity [Line Items]
Consolidated VIEs- Consolidated assets	2,283,000	2,694,000
Investment funds | Unconsolidated VIEs
Variable Interest Entity [Line Items]
Consolidated VIEs- Consolidated assets	2,346,000	2,299,000
Trust arrangements and other | Consolidated VIEs
Variable Interest Entity [Line Items]
Consolidated VIEs- Consolidated assets	¥ 5,557,000	¥ 19,000

Variable Interest Entities an_4

Variable Interest Entities and Securitizations (Carrying Amounts and Classification of Assets and Liabilities on Consolidated Balance Sheets that Relate to Variable Interests in Significant Unconsolidated VIEs) (Detail) - JPY (¥) ¥ in Millions		Sep. 30, 2020	Mar. 31, 2020
Assets on balance sheets related to unconsolidated VIEs:
Trading account assets		¥ 29,467,045	¥ 28,092,871
Loans		89,853,221	87,087,233
Total assets		217,594,620	211,218,760
Liabilities on balance sheets and maximum exposure to loss related to unconsolidated VIEs:
Payables under securities lending transactions		1,475,850	1,423,638
Trading account liabilities		10,590,312	12,416,785
Total		208,454,567	202,043,136
Maximum exposure to loss		491,000	521,000
Unconsolidated VIEs
Assets on balance sheets related to unconsolidated VIEs:
Total assets		2,423,000	2,376,000
Unconsolidated VIEs | Mizuho Financial Group Inc
Assets on balance sheets related to unconsolidated VIEs:
Trading account assets		113,000	108,000
Investments		231,000	267,000
Loans		58,000	55,000
Total assets		402,000	430,000
Liabilities on balance sheets and maximum exposure to loss related to unconsolidated VIEs:
Payables under securities lending transactions		48,000	47,000
Trading account liabilities		2,000	2,000
Total		50,000	49,000
Maximum exposure to loss	[1]	¥ 491,000	¥ 521,000
[1]	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.

Variable Interest Entities an_5

Variable Interest Entities and Securitizations - Additional Information (Detail) - JPY (¥) ¥ in Millions	Sep. 30, 2020	Mar. 31, 2020
Variable Interest Entity [Line Items]
Long-term debt	¥ 11,049,044	¥ 10,346,152
Noncontrolling interests	390,077	663,259
Consolidated VIEs
Variable Interest Entity [Line Items]
Noncontrolling interests	275,000	541,000
Debt Instrument [Member]
Variable Interest Entity [Line Items]
Long-term debt	317,000	356,000
Assets associated with securitization transactions
Variable Interest Entity [Line Items]
Transferred assets continue to be carried on the consolidated balance sheets	174,000	176,000
Assets associated with loan participation transactions
Variable Interest Entity [Line Items]
Transferred assets continue to be carried on the consolidated balance sheets	¥ 142,000	¥ 153,000

Summary of Noninterest Income (

Summary of Noninterest Income (Detail) - JPY (¥) ¥ in Millions		6 Months Ended
		Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Fee and commission income		¥ 428,317	¥ 403,992
Foreign exchange gains (losses)—net	[1]	22,785	27,923
Trading account gains (losses)—net	[2]	257,591	395,405
Investment gains (losses)—net:
Debt securities	[1]	46	31,092
Equity securities	[1]	266,119	(126,648)
Equity in earnings (losses) of equity method investees—net	[1]	5,788	22,066
Gains on disposal of premises and equipment	[1]	6,849	1,693
Other noninterest income	[2],[3]	23,715	34,839
Total noninterest income		1,011,210	790,362
Securities related business
Disaggregation of Revenue [Line Items]
Fee and commission income	[4]	78,441	64,498
Deposits related business
Disaggregation of Revenue [Line Items]
Fee and commission income	[4]	7,408	7,570
Lending related business
Disaggregation of Revenue [Line Items]
Fee and commission income	[2],[5]	79,619	68,609
Correspondent clearing
Disaggregation of Revenue [Line Items]
Fee and commission income	[4]	54,785	56,075
Investment advisory, management and administrative service
Disaggregation of Revenue [Line Items]
Fee and commission income	[4]	45,948	48,291
Fiduciary and trust
Disaggregation of Revenue [Line Items]
Fee and commission income	[4]	54,425	56,459
Agency business
Disaggregation of Revenue [Line Items]
Fee and commission income	[4]	15,064	15,152
Guarantee related business
Disaggregation of Revenue [Line Items]
Fee and commission income	[1]	15,560	13,898
Financial service, other
Disaggregation of Revenue [Line Items]
Fee and commission income	[4]	77,067	73,440
Financial service
Disaggregation of Revenue [Line Items]
Fee and commission income		¥ 428,317	¥ 403,992
[1]	These amounts are revenues from contracts that do not meet the scope of ASC 606.
[2]	Part of these amounts are considered to be revenues from contracts that are within the scope of ASC 606.
[3]	These amounts include the net unrealized gains resulting from changes in fair values of structured notes that contain embedded derivatives. See Note 17 “Fair value” for further details.
[4]	These amounts are revenues from contracts within the scope of ASC 606, “Revenue from contracts with customers” (“ASC 606”).
[5]	Most of the lending-related fees such as commitment fees and arrangement fees are not within the scope of ASC 606.

Noninterest Income - Additional

Noninterest Income - Additional Information (Detail) - JPY (¥) ¥ in Millions		6 Months Ended
		Sep. 30, 2020	Sep. 30, 2019
Other Revenues [Line Items]
Trust fees		¥ 25,000	¥ 25,000
Fees related to trust business		29,000	31,000
Trading account gains (losses)—net	[1]	257,591	395,405
Other noninterest income	[1],[2]	23,715	34,839
Revenue from contracts with customers ("ASC 606")
Other Revenues [Line Items]
Trading account gains (losses)—net		45,000	33,000
Other noninterest income		¥ 7,000	¥ 12,000
[1]	Part of these amounts are considered to be revenues from contracts that are within the scope of ASC 606.
[2]	These amounts include the net unrealized gains resulting from changes in fair values of structured notes that contain embedded derivatives. See Note 17 “Fair value” for further details.

Fair Value - Additional Informa

Fair Value - Additional Information (Detail) - JPY (¥) ¥ in Billions	6 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Mar. 31, 2020
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Carrying amounts of other equity interests of which fair value is not readily determinable	¥ 402		¥ 420
Net Derivative Asset Liability Measured On Recurring Basis Unobservable Inputs Reconciliation Transfers Into Level3	1
Net Derivative Asset Liability Measured On Recurring Basis Unobservable Inputs Reconciliation Transfers Out Of Level3	1
Senior borrowings and bonds
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
The differences between the aggregate fair value and aggregate unpaid principal balance of the notes for which the fair value option has been elected	61		¥ 112
Net unrealized gains (losses) resulting from changes in fair values of the notes	¥ 17	¥ 2
Investment funds
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Underlying assets, estimated remaining liquidation period	10 years
Long-term debt
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value of liabilities transferred out of Level 3	¥ 35	6
Fair value of liabilities transferred into Level 3	19	¥ 17
Trading securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value of assets transferred out of Level 3	¥ 1

Fair Value (Summary of Assets a

Fair Value (Summary of Assets and Liabilities Measured at Fair Value on a Recurring Basis, Including Fair Value Option Elected) (Detail) - JPY (¥) ¥ in Millions		Sep. 30, 2020	Mar. 31, 2020
Assets:
Available-for-sale securities		¥ 26,546,800	¥ 19,112,952
Liabilities:
Long-term debt		2,802,428	2,537,082
Fair Value, Measurements, Recurring
Assets:
Equity securities with readily determinable fair values		3,016,000	2,765,000
Equity securities measured at net asset value	[1]	83,000	72,000
Other investments		56,000	39,000
Total assets measured at fair value		59,168,000	50,081,000
Liabilities:
Trading securities sold, not yet purchased		2,339,000	2,395,000
Long-term debt	[2]	2,802,000	2,537,000
Total liabilities measured at fair value		13,392,000	14,953,000
Fair Value, Measurements, Recurring | Trading Account Asset
Assets:
Securities measured at net asset value	[1],[3]	447,000	462,000
Fair Value, Measurements, Recurring | Interest rate contracts
Assets:
Assets, derivatives		6,135,000	7,232,000
Liabilities:
Liabilities, derivatives		5,728,000	6,788,000
Fair Value, Measurements, Recurring | Foreign exchange contracts
Assets:
Assets, derivatives		2,143,000	2,926,000
Liabilities:
Liabilities, derivatives		2,160,000	2,899,000
Fair Value, Measurements, Recurring | Equity-related contracts
Assets:
Assets, derivatives		397,000	310,000
Liabilities:
Liabilities, derivatives		260,000	266,000
Fair Value, Measurements, Recurring | Credit-related contracts
Assets:
Assets, derivatives		55,000	30,000
Liabilities:
Liabilities, derivatives		77,000	29,000
Fair Value, Measurements, Recurring | Other contracts
Assets:
Assets, derivatives		28,000	38,000
Liabilities:
Liabilities, derivatives		26,000	39,000
Fair Value, Measurements, Recurring | Japanese government bonds
Assets:
Assets, trading securities	[3]	3,268,000	1,538,000
Available-for-sale securities		19,920,000	12,603,000
Fair Value, Measurements, Recurring | Japanese local government bonds
Assets:
Assets, trading securities	[3]	138,000	170,000
Available-for-sale securities		407,000	273,000
Fair Value, Measurements, Recurring | U.S. Treasury bonds and federal agency securities
Assets:
Assets, trading securities	[3]	5,792,000	5,041,000
Available-for-sale securities		627,000	935,000
Fair Value, Measurements, Recurring | Other foreign government bonds
Assets:
Assets, trading securities	[3]	1,464,000	1,675,000
Available-for-sale securities		1,356,000	1,411,000
Fair Value, Measurements, Recurring | Agency mortgage-backed securities
Assets:
Assets, trading securities	[3]	4,348,000	3,390,000
Available-for-sale securities		520,000	505,000
Fair Value, Measurements, Recurring | Residential mortgage-backed securities
Assets:
Assets, trading securities	[3]	9,000	10,000
Available-for-sale securities		80,000	84,000
Fair Value, Measurements, Recurring | Commercial mortgage-backed securities
Assets:
Available-for-sale securities		641,000	615,000
Fair Value, Measurements, Recurring | Certificates of deposit and commercial paper
Assets:
Assets, trading securities	[3]	1,259,000	1,036,000
Fair Value, Measurements, Recurring | Corporate bonds and other debt securities
Assets:
Assets, trading securities	[3],[4]	2,455,000	2,554,000
Fair Value, Measurements, Recurring | Equity securities
Assets:
Assets, trading securities	[3]	1,529,000	1,680,000
Fair Value, Measurements, Recurring | Japanese corporate bonds and other debt securities
Assets:
Available-for-sale securities		2,070,000	1,835,000
Fair Value, Measurements, Recurring | Foreign corporate bonds and other debt securities
Assets:
Available-for-sale securities		925,000	852,000
Fair Value, Measurements, Recurring | Level 1
Assets:
Equity securities with readily determinable fair values		2,976,000	2,670,000
Total assets measured at fair value		33,883,000	24,590,000
Liabilities:
Trading securities sold, not yet purchased		2,051,000	1,880,000
Total liabilities measured at fair value		2,222,000	2,243,000
Fair Value, Measurements, Recurring | Level 1 | Interest rate contracts
Assets:
Assets, derivatives		40,000	153,000
Liabilities:
Liabilities, derivatives		39,000	163,000
Fair Value, Measurements, Recurring | Level 1 | Foreign exchange contracts
Assets:
Assets, derivatives			9,000
Liabilities:
Liabilities, derivatives			8,000
Fair Value, Measurements, Recurring | Level 1 | Equity-related contracts
Assets:
Assets, derivatives		98,000	169,000
Liabilities:
Liabilities, derivatives		128,000	186,000
Fair Value, Measurements, Recurring | Level 1 | Other contracts
Assets:
Assets, derivatives		3,000	3,000
Liabilities:
Liabilities, derivatives		4,000	6,000
Fair Value, Measurements, Recurring | Level 1 | Japanese government bonds
Assets:
Assets, trading securities	[3]	3,257,000	1,516,000
Available-for-sale securities		19,600,000	11,950,000
Fair Value, Measurements, Recurring | Level 1 | U.S. Treasury bonds and federal agency securities
Assets:
Assets, trading securities	[3]	4,963,000	4,580,000
Available-for-sale securities		627,000	935,000
Fair Value, Measurements, Recurring | Level 1 | Other foreign government bonds
Assets:
Assets, trading securities	[3]	938,000	1,128,000
Available-for-sale securities		430,000	436,000
Fair Value, Measurements, Recurring | Level 1 | Corporate bonds and other debt securities
Assets:
Assets, trading securities	[3],[4]	22,000	41,000
Fair Value, Measurements, Recurring | Level 1 | Equity securities
Assets:
Assets, trading securities	[3]	929,000	1,000,000
Fair Value, Measurements, Recurring | Level 2
Assets:
Equity securities with readily determinable fair values		40,000	95,000
Total assets measured at fair value		22,181,000	22,712,000
Liabilities:
Trading securities sold, not yet purchased		268,000	515,000
Long-term debt	[2]	2,164,000	1,916,000
Total liabilities measured at fair value		10,462,000	12,008,000
Fair Value, Measurements, Recurring | Level 2 | Interest rate contracts
Assets:
Assets, derivatives		6,088,000	7,070,000
Liabilities:
Liabilities, derivatives		5,679,000	6,611,000
Fair Value, Measurements, Recurring | Level 2 | Foreign exchange contracts
Assets:
Assets, derivatives		2,123,000	2,900,000
Liabilities:
Liabilities, derivatives		2,159,000	2,890,000
Fair Value, Measurements, Recurring | Level 2 | Equity-related contracts
Assets:
Assets, derivatives		287,000	125,000
Liabilities:
Liabilities, derivatives		109,000	47,000
Fair Value, Measurements, Recurring | Level 2 | Credit-related contracts
Assets:
Assets, derivatives		52,000	22,000
Liabilities:
Liabilities, derivatives		75,000	19,000
Fair Value, Measurements, Recurring | Level 2 | Other contracts
Assets:
Assets, derivatives		10,000	11,000
Liabilities:
Liabilities, derivatives		8,000	10,000
Fair Value, Measurements, Recurring | Level 2 | Japanese government bonds
Assets:
Assets, trading securities	[3]	11,000	22,000
Available-for-sale securities		320,000	653,000
Fair Value, Measurements, Recurring | Level 2 | Japanese local government bonds
Assets:
Assets, trading securities	[3]	138,000	170,000
Available-for-sale securities		407,000	273,000
Fair Value, Measurements, Recurring | Level 2 | U.S. Treasury bonds and federal agency securities
Assets:
Assets, trading securities	[3]	829,000	461,000
Fair Value, Measurements, Recurring | Level 2 | Other foreign government bonds
Assets:
Assets, trading securities	[3]	526,000	547,000
Available-for-sale securities		926,000	975,000
Fair Value, Measurements, Recurring | Level 2 | Agency mortgage-backed securities
Assets:
Assets, trading securities	[3]	4,348,000	3,390,000
Available-for-sale securities		520,000	505,000
Fair Value, Measurements, Recurring | Level 2 | Residential mortgage-backed securities
Assets:
Available-for-sale securities		53,000	53,000
Fair Value, Measurements, Recurring | Level 2 | Certificates of deposit and commercial paper
Assets:
Assets, trading securities	[3]	1,259,000	1,036,000
Fair Value, Measurements, Recurring | Level 2 | Corporate bonds and other debt securities
Assets:
Assets, trading securities	[3],[4]	1,348,000	1,398,000
Fair Value, Measurements, Recurring | Level 2 | Equity securities
Assets:
Assets, trading securities	[3]	570,000	650,000
Fair Value, Measurements, Recurring | Level 2 | Japanese corporate bonds and other debt securities
Assets:
Available-for-sale securities		1,579,000	1,678,000
Fair Value, Measurements, Recurring | Level 2 | Foreign corporate bonds and other debt securities
Assets:
Available-for-sale securities		747,000	678,000
Fair Value, Measurements, Recurring | Level 3
Assets:
Other investments		56,000	39,000
Total assets measured at fair value		2,574,000	2,245,000
Liabilities:
Trading securities sold, not yet purchased		20,000
Long-term debt	[2]	638,000	621,000
Total liabilities measured at fair value		708,000	702,000
Fair Value, Measurements, Recurring | Level 3 | Interest rate contracts
Assets:
Assets, derivatives		7,000	9,000
Liabilities:
Liabilities, derivatives		10,000	14,000
Fair Value, Measurements, Recurring | Level 3 | Foreign exchange contracts
Assets:
Assets, derivatives		20,000	17,000
Liabilities:
Liabilities, derivatives		1,000	1,000
Fair Value, Measurements, Recurring | Level 3 | Equity-related contracts
Assets:
Assets, derivatives		12,000	16,000
Liabilities:
Liabilities, derivatives		23,000	33,000
Fair Value, Measurements, Recurring | Level 3 | Credit-related contracts
Assets:
Assets, derivatives		3,000	8,000
Liabilities:
Liabilities, derivatives		2,000	10,000
Fair Value, Measurements, Recurring | Level 3 | Other contracts
Assets:
Assets, derivatives		15,000	24,000
Liabilities:
Liabilities, derivatives		14,000	23,000
Fair Value, Measurements, Recurring | Level 3 | Residential mortgage-backed securities
Assets:
Assets, trading securities	[3]	9,000	10,000
Available-for-sale securities		27,000	31,000
Fair Value, Measurements, Recurring | Level 3 | Commercial mortgage-backed securities
Assets:
Available-for-sale securities		641,000	615,000
Fair Value, Measurements, Recurring | Level 3 | Corporate bonds and other debt securities
Assets:
Assets, trading securities	[3],[4]	1,085,000	1,115,000
Fair Value, Measurements, Recurring | Level 3 | Equity securities
Assets:
Assets, trading securities	[3]	30,000	30,000
Fair Value, Measurements, Recurring | Level 3 | Japanese corporate bonds and other debt securities
Assets:
Available-for-sale securities		491,000	157,000
Fair Value, Measurements, Recurring | Level 3 | Foreign corporate bonds and other debt securities
Assets:
Available-for-sale securities		¥ 178,000	¥ 174,000
[1]	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, 2020 and September 30, 2020 were ¥47 billion and ¥56 billion, respectively.
[2]	Amounts represent items for which the Group elected the fair value option or for which it applied the practicability exception.
[3]	Trading securities include foreign currency denominated securities for which the MHFG Group elected the fair value option.
[4]	The amount includes CLO and convertible bonds, which are classified in Level 3.

Fair Value (Summary of Assets_2

Fair Value (Summary of Assets and Liabilities Measured at Fair Value on a Recurring Basis, Including Fair Value Option Elected) (Parenthetical) (Detail) - JPY (¥) ¥ in Billions	Sep. 30, 2020	Mar. 31, 2020
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unfunded commitments	¥ 56	¥ 47

Fair Value (Reconciliation for

Fair Value (Reconciliation for All Assets and Liabilities Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs (Level 3)) (Detail) - JPY (¥) ¥ in Billions		6 Months Ended
		Sep. 30, 2020	Sep. 30, 2019
Other investments
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance			¥ 35
Gains (losses) in Earnings	[1]		1
Gains (losses) in OCI		¥ 0
Transfers into Level 3		0
Transfers out of level 3		0
Purchases			10
Sales		(1)	0
Issuances		0
Settlements			(10)
Ending Balance			36
Change in unrealized gain (losses) still held	[2]		2
Trading securities sold, not yet purchased
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance		0	1
Gains (losses) in Earnings	[3]	0
Gains (losses) in OCI		0
Transfers into Level 3		0
Transfers out of level 3		0
Purchases		0	(9)
Sales		20	8
Issuances		0
Settlements		0
Ending Balance		20
Change in unrealized gain (losses) still held		0
Long-term debt
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance		621	655
Gains (losses) in Earnings	[4]	(37)	(6)
Gains (losses) in OCI	[5]	(8)	0
Transfers into Level 3		19	17
Transfers out of level 3		(35)	(6)
Purchases		0
Sales		0
Issuances		108	108
Settlements		(120)	(134)
Ending Balance		638	646
Change in unrealized gain (losses) still held		(27)	(10)	[2]
Trading securities
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers out of level 3		(1)
Issuances		0
Trading securities | Residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance		10	11
Gains (losses) in Earnings	[3]	0
Gains (losses) in OCI		0
Transfers into Level 3		0
Transfers out of level 3		0
Purchases		0
Sales		0
Issuances		0
Settlements		(1)	(1)
Ending Balance		9	10
Change in unrealized gain (losses) still held		0
Trading securities | Corporate bonds and other debt securities
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance		1,115	1,044
Gains (losses) in Earnings	[3]	18	(15)
Gains (losses) in OCI		0
Transfers into Level 3		0
Transfers out of level 3		(1)
Purchases		189	338
Sales		(113)	(105)
Issuances		0
Settlements		(123)	(125)
Ending Balance		1,085	1,137
Change in unrealized gain (losses) still held		18	(14)	[2]
Trading securities | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance		30	28
Gains (losses) in Earnings	[3]	(2)	2
Gains (losses) in OCI		0
Transfers into Level 3		0
Transfers out of level 3		0
Purchases		2	1
Sales		0	0
Settlements		0	(1)
Ending Balance		30	30
Change in unrealized gain (losses) still held		(1)	0	[2]
Derivative financial instruments assets | Interest rate contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	[6]	(5)	13
Gains (losses) in Earnings	[3]	(3)	(9)	[6]
Gains (losses) in OCI	[6]	0
Transfers into Level 3	[6]	0
Transfers out of level 3	[6]	0
Purchases	[6]	0
Sales	[6]	0
Issuances	[6]	0
Settlements	[6]	5	1
Ending Balance	[6]	(3)	5
Change in unrealized gain (losses) still held	[6]	1	(8)	[2]
Derivative financial instruments assets | Foreign exchange contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	[6]	16	22
Gains (losses) in Earnings	[3]	4	(10)	[6]
Gains (losses) in OCI	[6]	0
Transfers into Level 3	[6]	0
Transfers out of level 3	[6]	0
Purchases	[6]	0
Sales	[6]	0
Issuances	[6]	0
Settlements	[6]	(1)	(2)
Ending Balance	[6]	19	10
Change in unrealized gain (losses) still held	[6]	5	(9)	[2]
Derivative financial instruments assets | Equity-related contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	[6]	(17)	(5)
Gains (losses) in Earnings	[3]	4	1	[6]
Gains (losses) in OCI	[6]	0
Transfers into Level 3	[6]	0
Transfers out of level 3	[6]	0
Purchases	[6]	0
Sales	[6]	0
Issuances	[6]	0
Settlements	[6]	2	(3)
Ending Balance	[6]	(11)	(7)
Change in unrealized gain (losses) still held	[6]	3	2	[2]
Derivative financial instruments assets | Credit-related contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	[6]	(2)	1
Gains (losses) in Earnings	[3]	3
Gains (losses) in OCI	[6]	0
Transfers into Level 3	[6]	1
Transfers out of level 3	[6]	1
Purchases	[6]	0
Sales	[6]	0
Issuances	[6]	0
Settlements	[6]	(2)
Ending Balance	[6]	1	1
Change in unrealized gain (losses) still held	[6]	1
Derivative financial instruments assets | Other contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	[6]	1	1
Gains (losses) in Earnings	[3]	0
Gains (losses) in OCI	[6]	0
Transfers into Level 3	[6]	0
Transfers out of level 3	[6]	0
Purchases	[6]	0
Sales	[6]	0
Issuances	[6]	0
Settlements	[6]	0
Ending Balance	[6]	1	1
Change in unrealized gain (losses) still held	[6]	0
Available-for-sale securities | Residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance		31	40
Gains (losses) in Earnings	[1]	0
Gains (losses) in OCI	[5]	0
Transfers into Level 3		0
Transfers out of level 3		0
Purchases		0
Sales		0
Issuances		0
Settlements		(4)	(7)
Ending Balance		27	33
Change in unrealized gain (losses) still held		0
Available-for-sale securities | Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance		615	500
Gains (losses) in Earnings	[1]	0
Gains (losses) in OCI	[5]	1	1
Transfers into Level 3		0
Transfers out of level 3		0
Purchases		78	89
Sales		(51)	(35)
Issuances		0
Settlements		(2)	(6)
Ending Balance		641	549
Change in unrealized gain (losses) still held		0
Available-for-sale securities | Japanese corporate bonds and other debt securities
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance		157	120
Gains (losses) in Earnings	[1]	(7)	1
Gains (losses) in OCI	[5]	8	4
Transfers into Level 3		0
Transfers out of level 3		0
Purchases		344	97
Sales		0	0
Issuances		0
Settlements		(11)	(53)
Ending Balance		491	169
Change in unrealized gain (losses) still held		0
Available-for-sale securities | Foreign corporate bonds and other debt securities
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance		174	103
Gains (losses) in Earnings	[1]	1
Gains (losses) in OCI	[5]	8	(5)
Transfers into Level 3		0
Transfers out of level 3		0
Purchases		31	38
Sales		0
Issuances		0
Settlements		(36)	(3)
Ending Balance		178	¥ 133
Change in unrealized gain (losses) still held		0
Available-for-sale securities | Other investments
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance		39
Gains (losses) in Earnings	[1]	(1)
Purchases		38
Settlements		(19)
Ending Balance		56
Change in unrealized gain (losses) still held		¥ (1)
[1]	Gains (losses) in Earnings are reported in Investment gains (losses)-net.
[2]	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 September 30, 2019 and 2020.The amounts of unrealized gains (losses) in OCI related to Available-for-sale securities and Long-term debt were ¥7 billion and ¥(8) billion, at September 30, 2020, respectively.
[3]	Gains (losses) in Earnings are reported in Trading account gains (losses)-net, Foreign exchange gains (losses)-net or Other noninterest income (expenses).
[4]	Gains (losses) in Earnings are reported in Other noninterest income (expenses).
[5]	Gains (losses) in OCI are reported in Other comprehensive income (loss).
[6]	Total Level 3 derivative exposures have been netted on the table for presentation purposes only.

Fair Value (Reconciliation fo_2

Fair Value (Reconciliation for All Assets and Liabilities Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs (Level 3)) (Parenthetical) (Detail) ¥ in Billions	Sep. 30, 2020JPY (¥)
Fair Value Disclosures [Abstract]
unrealized gains (losses) in OCI related to Available-for-sale securities	¥ 7
unrealized gains (losses) in OCI related to Long-term debt	¥ (8)

Fair Value (Quantitative Inform

Fair Value (Quantitative Information about Significant Unobservable Inputs Related to Material Classes of Level 3 Assets and Liabilities) (Detail) ¥ in Millions		Sep. 30, 2020JPY (¥)		Mar. 31, 2020JPY (¥)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Long-term debt		¥ 2,802,428		¥ 2,537,082
Available For Sale And Trading Securities | Residential mortgage-backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading securities		36,000		41,000
Available For Sale And Trading Securities | Commercial mortgage-backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading securities		641,000		615,000
Available For Sale And Trading Securities | Corporate bonds and other debt securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading securities		1,754,000		1,446,000
Derivative Financial Instruments | Interest rate contracts
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivatives financial instruments		(3,000)		(5,000)
Derivative Financial Instruments | Foreign exchange contracts
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivatives financial instruments		19,000		16,000
Derivative Financial Instruments | Equity-related contracts
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivatives financial instruments		(11,000)		(17,000)
Derivative Financial Instruments | Credit-related contracts
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivatives financial instruments		1,000		(2,000)
Derivative Financial Instruments | Other contracts
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivatives financial instruments		1,000
Long-term debt
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Long-term debt		¥ 638,000		¥ 621,000
Minimum | Other contracts | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading securities		0
Minimum | Measurement Input, Prepayment Rate [Member] | Available For Sale And Trading Securities | Residential mortgage-backed securities | Discounted Cash Flows Valuation Technique [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading securities		3		4
Minimum | Measurement Input, Prepayment Rate [Member] | Available For Sale And Trading Securities | Corporate bonds and other debt securities | Discounted Cash Flows Valuation Technique [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading securities	[1]	1		13
Minimum | Measurement Input, Default Rate [Member] | Available For Sale And Trading Securities | Residential mortgage-backed securities | Discounted Cash Flows Valuation Technique [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading securities		0		0
Minimum | Measurement Input, Default Rate [Member] | Available For Sale And Trading Securities | Corporate bonds and other debt securities | Discounted Cash Flows Valuation Technique [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading securities	[1]	0		0
Minimum | Measurement Input, Default Rate [Member] | Derivative Financial Instruments | Interest rate contracts | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivatives financial instruments	[2],[3]			0
Minimum | Measurement Input, Default Rate [Member] | Derivative Financial Instruments | Foreign exchange contracts | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivatives financial instruments	[2],[3]			0
Minimum | Measurement Input, Default Rate [Member] | Derivative Financial Instruments | Credit-related contracts | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivatives financial instruments	[2]	0		0
Minimum | Measurement Input, Default Rate [Member] | Long-term debt | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Long-term debt	[2]	0		0
Minimum | Measurement Input Recovery Rate [Member] | Available For Sale And Trading Securities | Residential mortgage-backed securities | Discounted Cash Flows Valuation Technique [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading securities		100		100
Minimum | Measurement Input Recovery Rate [Member] | Available For Sale And Trading Securities | Corporate bonds and other debt securities | Discounted Cash Flows Valuation Technique [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading securities	[1]	10		10
Minimum | Measurement Input, Discount Rate [Member] | Available For Sale And Trading Securities | Residential mortgage-backed securities | Discounted Cash Flows Valuation Technique [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading securities		5		5
Minimum | Measurement Input, Discount Rate [Member] | Available For Sale And Trading Securities | Corporate bonds and other debt securities | Discounted Cash Flows Valuation Technique [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading securities	[1]	25		61
Minimum | Measurement Input Discount Rate1 [Member] | Available For Sale And Trading Securities | Commercial mortgage-backed securities | Discounted Cash Flows Valuation Technique [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading securities		6		7
Minimum | Measurement Input Discount Rate1 [Member] | Available For Sale And Trading Securities | Corporate bonds and other debt securities | Discounted Cash Flows Valuation Technique [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading securities		4	[1]	5	[4]
Minimum | Measurement Input, IR - IR correlation [Member] | Derivative Financial Instruments | Interest rate contracts | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivatives financial instruments	[2]	23		23
Minimum | Measurement Input, IR - IR correlation [Member] | Long-term debt | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Long-term debt	[2]	23		23
Minimum | Measurement Input, FX - IR correlation [Member] | Derivative Financial Instruments | Foreign exchange contracts | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivatives financial instruments	[2]	27		(37)
Minimum | Measurement Input, FX - IR correlation [Member] | Long-term debt | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Long-term debt	[2]	27		(37)
Minimum | Measurement Input, FX - FX correlation [Member] | Derivative Financial Instruments | Foreign exchange contracts | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivatives financial instruments	[2]	46		56
Minimum | Measurement Input, FX - FX correlation [Member] | Long-term debt | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Long-term debt	[2]	46		56
Minimum | Measurement Input, Equity - IR correlation [Member] | Derivative Financial Instruments | Equity-related contracts | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivatives financial instruments	[2]	25		25
Minimum | Measurement Input, Equity - IR correlation [Member] | Long-term debt | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Long-term debt	[2]	25		25
Minimum | Measurement Input, Equity - FX correlation [Member] | Long-term debt | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Long-term debt	[2]	33		(33)
Minimum | Measurement Input, Equity volatility [Member] | Derivative Financial Instruments | Equity-related contracts | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivatives financial instruments	[2]	12		13
Minimum | Measurement Input, Equity volatility [Member] | Long-term debt | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Long-term debt	[2]	13		15
Minimum | Measurement Input, Credit correlation [Member] | Derivative Financial Instruments | Credit-related contracts | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivatives financial instruments	[2]	35		30
Minimum | Measurement Input, Credit correlation [Member] | Long-term debt | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Long-term debt	[2]	18		15
Minimum | Measurement Input, Equity correlation [Member] | Derivative Financial Instruments | Equity-related contracts | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivatives financial instruments	[2]	0		0
Minimum | Measurement Input, Equity correlation [Member] | Long-term debt | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Long-term debt	[2]	0		0
Maximum | Other contracts | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading securities		57
Maximum | Measurement Input, Prepayment Rate [Member] | Available For Sale And Trading Securities | Residential mortgage-backed securities | Discounted Cash Flows Valuation Technique [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading securities		16		16
Maximum | Measurement Input, Prepayment Rate [Member] | Available For Sale And Trading Securities | Corporate bonds and other debt securities | Discounted Cash Flows Valuation Technique [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading securities	[1]	22		21
Maximum | Measurement Input, Default Rate [Member] | Residential mortgage-backed securities | Discounted Cash Flows Valuation Technique [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading securities				1
Maximum | Measurement Input, Default Rate [Member] | Available For Sale And Trading Securities | Residential mortgage-backed securities | Discounted Cash Flows Valuation Technique [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading securities		1
Maximum | Measurement Input, Default Rate [Member] | Available For Sale And Trading Securities | Corporate bonds and other debt securities | Discounted Cash Flows Valuation Technique [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading securities	[1]	3		2
Maximum | Measurement Input, Default Rate [Member] | Derivative Financial Instruments | Interest rate contracts | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivatives financial instruments	[2],[3]			63
Maximum | Measurement Input, Default Rate [Member] | Derivative Financial Instruments | Foreign exchange contracts | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivatives financial instruments	[2],[3]			63
Maximum | Measurement Input, Default Rate [Member] | Derivative Financial Instruments | Credit-related contracts | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivatives financial instruments	[2]	7		15
Maximum | Measurement Input, Default Rate [Member] | Long-term debt | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Long-term debt	[2]	6		12
Maximum | Measurement Input Recovery Rate [Member] | Available For Sale And Trading Securities | Residential mortgage-backed securities | Discounted Cash Flows Valuation Technique [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading securities		100		100
Maximum | Measurement Input Recovery Rate [Member] | Available For Sale And Trading Securities | Corporate bonds and other debt securities | Discounted Cash Flows Valuation Technique [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading securities	[1]	69		70
Maximum | Measurement Input, Discount Rate [Member] | Available For Sale And Trading Securities | Residential mortgage-backed securities | Discounted Cash Flows Valuation Technique [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading securities		170		170
Maximum | Measurement Input, Discount Rate [Member] | Available For Sale And Trading Securities | Corporate bonds and other debt securities | Discounted Cash Flows Valuation Technique [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading securities	[1]	173		1,160
Maximum | Measurement Input Discount Rate1 [Member] | Available For Sale And Trading Securities | Commercial mortgage-backed securities | Discounted Cash Flows Valuation Technique [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading securities		185		185
Maximum | Measurement Input Discount Rate1 [Member] | Available For Sale And Trading Securities | Corporate bonds and other debt securities | Discounted Cash Flows Valuation Technique [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading securities		696	[1]	1,528	[4]
Maximum | Measurement Input, IR - IR correlation [Member] | Derivative Financial Instruments | Interest rate contracts | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivatives financial instruments	[2]	100		100
Maximum | Measurement Input, IR - IR correlation [Member] | Long-term debt | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Long-term debt	[2]	100		100
Maximum | Measurement Input, FX - IR correlation [Member] | Derivative Financial Instruments | Foreign exchange contracts | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivatives financial instruments	[2]	52		49
Maximum | Measurement Input, FX - IR correlation [Member] | Long-term debt | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Long-term debt	[2]	52		50
Maximum | Measurement Input, FX - FX correlation [Member] | Derivative Financial Instruments | Foreign exchange contracts | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivatives financial instruments	[2]	63		65
Maximum | Measurement Input, FX - FX correlation [Member] | Long-term debt | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Long-term debt	[2]	63		65
Maximum | Measurement Input, Equity - IR correlation [Member] | Derivative Financial Instruments | Equity-related contracts | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivatives financial instruments	[2]	25		25
Maximum | Measurement Input, Equity - IR correlation [Member] | Long-term debt | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Long-term debt	[2]	25		25
Maximum | Measurement Input, Equity - FX correlation [Member] | Long-term debt | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Long-term debt	[2]	100		100
Maximum | Measurement Input, Equity volatility [Member] | Derivative Financial Instruments | Equity-related contracts | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivatives financial instruments	[2]	96		157
Maximum | Measurement Input, Equity volatility [Member] | Long-term debt | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Long-term debt	[2]	96		157
Maximum | Measurement Input, Credit correlation [Member] | Derivative Financial Instruments | Credit-related contracts | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivatives financial instruments	[2]	100		100
Maximum | Measurement Input, Credit correlation [Member] | Long-term debt | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Long-term debt	[2]	100		100
Maximum | Measurement Input, Equity correlation [Member] | Derivative Financial Instruments | Equity-related contracts | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivatives financial instruments	[2]	100		100
Maximum | Measurement Input, Equity correlation [Member] | Long-term debt | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Long-term debt	[2]	100		100
Weighted Average | Other contracts | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivatives financial instruments	[5]	36
Weighted Average | Measurement Input, Prepayment Rate [Member] | Available For Sale And Trading Securities | Residential mortgage-backed securities | Discounted Cash Flows Valuation Technique [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading securities	[5]	7		7
Weighted Average | Measurement Input, Prepayment Rate [Member] | Available For Sale And Trading Securities | Corporate bonds and other debt securities | Discounted Cash Flows Valuation Technique [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading securities	[5]	19		21
Weighted Average | Measurement Input, Default Rate [Member] | Credit-related contracts | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivatives financial instruments	[5]	1
Weighted Average | Measurement Input, Default Rate [Member] | Available For Sale And Trading Securities | Residential mortgage-backed securities | Discounted Cash Flows Valuation Technique [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading securities	[5]	0		0
Weighted Average | Measurement Input, Default Rate [Member] | Available For Sale And Trading Securities | Corporate bonds and other debt securities | Discounted Cash Flows Valuation Technique [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading securities	[5]	1		2
Weighted Average | Measurement Input, Default Rate [Member] | Long-term debt | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Long-term debt	[5]	2
Weighted Average | Measurement Input Recovery Rate [Member] | Available For Sale And Trading Securities | Residential mortgage-backed securities | Discounted Cash Flows Valuation Technique [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading securities	[5]	100		100
Weighted Average | Measurement Input Recovery Rate [Member] | Available For Sale And Trading Securities | Corporate bonds and other debt securities | Discounted Cash Flows Valuation Technique [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading securities	[5]	67		67
Weighted Average | Measurement Input, Discount Rate [Member] | Available For Sale And Trading Securities | Residential mortgage-backed securities | Discounted Cash Flows Valuation Technique [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading securities	[5]	50		52
Weighted Average | Measurement Input, Discount Rate [Member] | Available For Sale And Trading Securities | Corporate bonds and other debt securities | Discounted Cash Flows Valuation Technique [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading securities	[5]	123		256
Weighted Average | Measurement Input Discount Rate1 [Member] | Available For Sale And Trading Securities | Commercial mortgage-backed securities | Discounted Cash Flows Valuation Technique [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading securities	[5]	21		22
Weighted Average | Measurement Input Discount Rate1 [Member] | Available For Sale And Trading Securities | Corporate bonds and other debt securities | Discounted Cash Flows Valuation Technique [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Trading securities	[5]	233		58
Weighted Average | Measurement Input, IR - IR correlation [Member] | Derivative Financial Instruments | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivatives financial instruments	[5]	76
Weighted Average | Measurement Input, IR - IR correlation [Member] | Long-term debt | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Long-term debt	[5]	76
Weighted Average | Measurement Input, FX - IR correlation [Member] | Foreign exchange contracts | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivatives financial instruments	[5]	28
Weighted Average | Measurement Input, FX - IR correlation [Member] | Long-term debt
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Long-term debt	[5]	35
Weighted Average | Measurement Input, FX - FX correlation [Member] | Foreign exchange contracts | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivatives financial instruments	[5]	55
Weighted Average | Measurement Input, FX - FX correlation [Member] | Long-term debt
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Long-term debt	[5]	55
Weighted Average | Measurement Input, Equity - IR correlation [Member] | Equity-related contracts | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivatives financial instruments	[5]	25
Weighted Average | Measurement Input, Equity - IR correlation [Member] | Long-term debt
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Long-term debt	[5]	25
Weighted Average | Measurement Input, Equity - FX correlation [Member] | Equity-related contracts | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivatives financial instruments	[5]	88
Weighted Average | Measurement Input, Equity - FX correlation [Member] | Long-term debt
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Long-term debt	[5]	(3)
Weighted Average | Measurement Input, Equity volatility [Member] | Equity-related contracts | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivatives financial instruments	[5]	43
Weighted Average | Measurement Input, Equity volatility [Member] | Long-term debt
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Long-term debt	[5]	29
Weighted Average | Measurement Input, Credit correlation [Member] | Credit-related contracts | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivatives financial instruments	[5]	66
Weighted Average | Measurement Input, Credit correlation [Member] | Long-term debt | Internal Valuation Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Long-term debt	[5]	66
Weighted Average | Measurement Input, Equity correlation [Member] | Long-term debt
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Long-term debt	[5]	86
[1]	These inputs are mainly used for determining the fair values of securitization products such as CDO, CLO and ABS, other than RMBS and CMBS.
[2]	Internal valuation model includes discounted cash flow models and the Black-Scholes option pricing model.
[3]	This input represents the counterparty default rate derived from the MHFG Group’s own internal credit analyses.
[4]	This input is mainly used for determining the fair values of Japanese corporate bonds and foreign corporate bonds.
[5]	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.

Fair Value (Summary of Assets_3

Fair Value (Summary of Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis) (Detail) - JPY (¥) ¥ in Millions	Sep. 30, 2020	Mar. 31, 2020
Assets:
Equity securities (without readily determinable fair values)	¥ 402,194	¥ 419,775
Fair Value, Measurements, Nonrecurring
Assets:
Loans	131,000	90,000
Loans held-for-sale	17,000	26,000
Equity securities (without readily determinable fair values)	1,000	2,000
Other investments	52,000
Premises and equipment-net	0	1,000
Total assets measured at fair value	201,000	119,000
Fair Value, Measurements, Nonrecurring | Aggregate cost
Assets:
Loans	200,000	136,000
Loans held-for-sale	18,000	26,000
Equity securities (without readily determinable fair values)	2,000	2,000
Other investments	59,000
Premises and equipment-net	1,000	12,000
Other assets		3,000
Goodwill		2,000
Total assets measured at fair value	280,000	181,000
Fair Value, Measurements, Nonrecurring | Level 1
Assets:
Loans	0
Loans held-for-sale	0
Equity securities (without readily determinable fair values)	0
Other investments	31,000
Premises and equipment-net	0
Total assets measured at fair value	31,000	0
Fair Value, Measurements, Nonrecurring | Level 2
Assets:
Loans	2,000	0
Loans held-for-sale	11,000	20,000
Equity securities (without readily determinable fair values)	0
Other investments	0
Premises and equipment-net	0	1,000
Total assets measured at fair value	13,000	21,000
Fair Value, Measurements, Nonrecurring | Level 3
Assets:
Loans	129,000	90,000
Loans held-for-sale	6,000	6,000
Equity securities (without readily determinable fair values)	1,000	2,000
Other investments	21,000
Premises and equipment-net	0	0
Total assets measured at fair value	¥ 157,000	¥ 98,000

Fair Value (Carrying Amounts an

Fair Value (Carrying Amounts and Fair Values of Certain Financial Instruments, Excluding Financial Instruments Carried at Fair Value on a Recurring Basis and Those outside Scope of ASC 825) (Detail) - JPY (¥) ¥ in Millions		Sep. 30, 2020	Mar. 31, 2020
Financial liabilities:
Long-term debt		¥ 2,802,428	¥ 2,537,082
Carrying amount
Financial assets:
Cash and due from banks, interest-bearing deposits in other banks, call loans and funds sold, and receivables under resale agreements and securities borrowing transactions		58,623,000	63,755,000
Investments		790,000	862,000
Loans, net of allowance	[1]	89,611,000	86,914,000
Financial liabilities:
Noninterest-bearing deposits, call money and funds purchased, and payables under repurchase agreements and securities lending transactions		53,640,000	51,954,000
Interest-bearing deposits		118,333,000	114,653,000
Due to trust accounts		564,000	250,000
Other short-term borrowings		7,526,000	4,914,000
Long-term debt		8,266,000	7,821,000
Estimated fair value
Financial assets:
Cash and due from banks, interest-bearing deposits in other banks, call loans and funds sold, and receivables under resale agreements and securities borrowing transactions		58,623,000	63,755,000
Investments		812,000	875,000
Loans, net of allowance	[1]	90,983,000	88,124,000
Financial liabilities:
Noninterest-bearing deposits, call money and funds purchased, and payables under repurchase agreements and securities lending transactions		53,640,000	51,954,000
Interest-bearing deposits		118,347,000	114,659,000
Due to trust accounts		564,000	250,000
Other short-term borrowings		7,526,000	4,914,000
Long-term debt		8,493,000	7,708,000
Estimated fair value | Level 1
Financial assets:
Cash and due from banks, interest-bearing deposits in other banks, call loans and funds sold, and receivables under resale agreements and securities borrowing transactions		42,233,000	1,318,000
Investments		491,000	493,000
Financial liabilities:
Noninterest-bearing deposits, call money and funds purchased, and payables under repurchase agreements and securities lending transactions			29,812,000
Interest-bearing deposits			58,935,000
Estimated fair value | Level 2
Financial assets:
Cash and due from banks, interest-bearing deposits in other banks, call loans and funds sold, and receivables under resale agreements and securities borrowing transactions		16,390,000	62,437,000
Investments		321,000	382,000
Financial liabilities:
Noninterest-bearing deposits, call money and funds purchased, and payables under repurchase agreements and securities lending transactions		53,640,000	22,142,000
Interest-bearing deposits		118,347,000	55,724,000
Due to trust accounts		564,000	250,000
Other short-term borrowings		7,526,000	4,914,000
Long-term debt		7,155,000	6,813,000
Estimated fair value | Level 3
Financial assets:
Loans, net of allowance	[1]	90,983,000	88,124,000
Financial liabilities:
Long-term debt		¥ 1,338,000	¥ 895,000
[1]	Loans, net of allowance include items measured at fair value on a nonrecurring basis.

Offsetting of Financial Asset_3

Offsetting of Financial Assets and Financial Liabilities (Information of Offsetting of Financial Assets and Financial Liabilities) (Detail) - JPY (¥) ¥ in Billions		Sep. 30, 2020		Mar. 31, 2020	[1]
Offsetting Financial Assets And Financial Liabilities [Line Items]
Derivative assets, Gross amounts recognized		¥ 8,758		¥ 9,819
Derivative assets, Gross amounts offset on the balance sheet		0		0
Derivative assets, Net amounts presented on the balance sheet	[2]	8,758	[3]	9,819
Derivative assets, Amounts not offset on the balance sheet, Financial instruments	[4],[5]	(6,373)		(7,723)
Derivative assets, Amounts not offset on the balance sheet, Cash collateral	[4]	(486)		(629)
Derivative assets, Net amounts		1,899		1,467
Receivables under resale agreements, Gross amounts recognized		12,666		17,347
Receivables under resale agreements, Gross amounts offset on the balance sheet		0		0
Receivables under resale agreements, Net amounts presented on the balance sheet	[2]	12,666	[6]	17,347
Receivables under resale agreements, Amounts not offset on the balance sheet, Financial instruments	[4],[5]	(11,479)		(17,197)
Receivables under resale agreements, Amounts not offset on the balance sheet, Cash collateral	[4]	0		0
Receivables under resale agreements, Net amounts		1,187		150
Receivables under securities borrowing transactions, Gross amounts recognized		2,186		1,753
Receivables under securities borrowing transactions, Gross amounts offset on the balance sheet		0		0
Receivables under securities borrowing transactions, Net amounts presented on the balance sheet	[2]	2,186	[7]	1,753
Receivables under securities borrowing transactions, Amounts not offset on the balance sheet, Financial instruments	[4],[5]	(1,846)		(1,709)
Receivables under securities borrowing transactions, Amounts not offset on the balance sheet, Cash collateral	[4]	0		0
Receivables under securities borrowing transactions, Net amounts		340		44
Financial assets, Gross amounts recognized, Total		23,610		28,919
Financial assets, Gross amounts offset on the balance sheet, Total		0		0
Financial assets, Net amounts presented on the balance sheet, Total	[2]	23,610		28,919
Financial assets, Amounts not offset on the balance sheet, Financial instruments, Total	[4],[5]	(19,698)		(26,629)
Financial assets, Amounts not offset on the balance sheet, Cash collateral, Total	[4]	(486)		(629)
Financial assets, Net amounts, Total		3,426		1,661
Derivative liabilities, Gross amounts recognized		8,251		9,220
Derivative liabilities, Gross amounts offset on the balance sheet		0		0
Derivative liabilities, Net amounts presented on the balance sheet	[2]	8,251	[3]	9,220
Derivative liabilities, Amounts not offset on the balance sheet, Financial instruments	[4],[5]	(6,148)		(7,519)
Derivative liabilities, Amounts not offset on the balance sheet, Cash collateral	[4]	(930)		(1,215)
Derivative liabilities, Net amounts		1,173		486
Payables under repurchase agreements, Gross amounts recognized		19,326		17,542
Payables under repurchase agreements, Gross amounts offset on the balance sheet		0		0
Payables under repurchase agreements, Net amounts presented on the balance sheet	[2]	19,326	[6]	17,542
Payables under repurchase agreements, Amounts not offset on the balance sheet, Financial instruments	[4],[5]	(18,038)		(17,191)
Payables under repurchase agreements, Amounts not offset on the balance sheet, Cash collateral	[4]	0		0
Payables under repurchase agreements, Net amounts		1,288		351
Payables under securities lending transactions, Gross amounts recognized		1,476		626
Payables under securities lending transactions, Gross amounts offset on the balance sheet		0		0
Payables under securities lending transactions, Net amounts presented on the balance sheet	[2]	1,476	[7]	626
Payables under securities lending transactions, Amounts not offset on the balance sheet, Financial instruments	[4],[5]	(1,235)		(623)
Payables under securities lending transactions, Amounts not offset on the balance sheet, Cash collateral	[4]	0		0
Payables under securities lending transactions, Net amounts		241		3
Financial liabilities, Gross amounts recognized, Total		29,053		27,388
Financial liabilities, Gross amounts offset on the balance sheet, Total		0		0
Financial liabilities, Net amounts presented on the balance sheet, Total	[2]	29,053		27,388
Financial liabilities, Amounts not offset on the balance sheet, Financial instruments, Total	[4],[5]	(25,421)		(25,333)
Financial liabilities, Amounts not offset on the balance sheet, Cash collateral, Total	[4]	(930)		(1,215)
Financial liabilities, Net amounts, Total		¥ 2,702		¥ 840
[1]	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.
[2]	Derivative assets and liabilities are recorded in Trading account assets and Trading account liabilities, respectively.
[3]	The amounts of derivative assets and liabilities subject to enforceable master netting arrangements or similar agreements at September 30, 2020 were ¥8,154 billion and ¥7,528 billion, respectively.
[4]	Amounts do not exceed the net amounts presented on the balance sheet and do not include the effect of overcollateralization, where it exists.
[5]	For derivatives, amounts include derivative assets or liabilities and securities collateral that are eligible for offsetting under enforceable master netting arrangements or similar agreements.
[6]	The amounts of Receivables under resale agreements and Payables under repurchase agreements subject to enforceable industry standard master repurchase agreements with netting terms at September 30, 2020 were ¥11,490 billion and ¥18,755 billion, respectively.
[7]	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 at September 30, 2020 were ¥1,915 billion and ¥1,243 billion, respectively.

Offsetting of Financial Asset_4

Offsetting of Financial Assets and Financial Liabilities (Information of Offsetting of Financial Assets and Financial Liabilities) (Parenthetical) (Detail) ¥ in Billions	Sep. 30, 2020JPY (¥)
Offsetting Financial Assets And Financial Liabilities [Line Items]
Receivables under resale agreement subject to enforceable master netting arrangements	¥ 11,490
Payables under repurchase agreement subject to enforceable master netting arrangements	18,755
Receivables under securities transaction borrowing subject to master netting arrangement	1,915
Payables under securities transaction lending subject to master netting arragement	1,243
Subject To Enforceable Master Netting Arragement [Member]
Offsetting Financial Assets And Financial Liabilities [Line Items]
Derivative assets subject to enforceable master netting arrangements	8,154
Derivative liabilities subject to enforceable master netting arrangements	¥ 7,528

Repurchase Agreements and Sec_3

Repurchase Agreements and Securities Lending Transactions Accounted for as Secured Borrowings (Gross Amounts of Liabilities by Remaining Contractual Maturity) (Detail) - JPY (¥) ¥ in Billions		Sep. 30, 2020	Mar. 31, 2020
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements	[1]	¥ 19,326	¥ 17,971
Securities lending transactions	[1]	1,476	1,424
Total		20,802	19,395
Overnight and continuous
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		10,154	6,357
Securities lending transactions		798	877
Total		10,952	7,234
Up to 30 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		3,684	5,467
Securities lending transactions		298	231
Total		3,982	5,698
31 to 90 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		3,162	4,867
Securities lending transactions		50
Total		3,212	4,867
Greater than 90 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		2,326	1,280
Securities lending transactions		330	316
Total		¥ 2,656	¥ 1,596
[1]	Amounts exceeded the gross amounts recognized in Note 18 “Offsetting of financial assets and financial liabilities” by ¥1,227 billion and ¥804 billion, at March 31, 2020 and September 30, 2020, respectively, which excluded the amounts relating to master netting agreements or similar agreements where the MHFG Group did not have the legal right of set-off or where uncertainty exists as to the enforceability.

Repurchase Agreements and Sec_4

Repurchase Agreements and Securities Lending Transactions Accounted for as Secured Borrowings (Gross Amounts of Liabilities by Class of Underlying Collateral) (Detail) - JPY (¥) ¥ in Billions		Sep. 30, 2020	Mar. 31, 2020
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements	[1]	¥ 19,326	¥ 17,971
Securities lending transactions	[1]	1,476	1,424
Japanese government bonds and Japanese local government bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		3,355	1,790
Securities lending transactions		372	269
Foreign government bonds and foreign agency mortgage-backed securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		15,100	15,218
Securities lending transactions		368	359
Commercial Paper and Corporate Bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		209	273
Securities lending transactions		53	50
Equity Securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		579	542
Securities lending transactions		668	730
Other securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		83	148
Securities lending transactions		¥ 15	¥ 16
[1]	Amounts exceeded the gross amounts recognized in Note 18 “Offsetting of financial assets and financial liabilities” by ¥1,227 billion and ¥804 billion, at March 31, 2020 and September 30, 2020, respectively, which excluded the amounts relating to master netting agreements or similar agreements where the MHFG Group did not have the legal right of set-off or where uncertainty exists as to the enforceability.

Repurchase Agreements and Sec_5

Repurchase Agreements and Securities Lending Transactions Accounted for as Secured Borrowings (Gross Amounts of Liabilities by Class of Underlying Collateral) (Parenthetical) (Detail) - JPY (¥) ¥ in Billions	Sep. 30, 2020	Mar. 31, 2020
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Amounts exceeded the gross amounts recognized in offsetting of financial assets and financial liabilities	¥ 804	¥ 1,227

Repurchase Agreements and Sec_6

Repurchase Agreements and Securities Lending Transactions Accounted for as Secured Borrowings - Additional Information (Detail)	Sep. 30, 2020	Mar. 31, 2020
Brokers and Dealers [Abstract]
Assets Pledged As Collateral As A Percentage Of Total Assets	5.00%	2.00%

Business Segment Information -

Business Segment Information - Additional Information (Detail)	6 Months Ended
	Sep. 30, 2020Segment
Segment Reporting Information [Line Items]
Number of operating segments	5

Business Segment Information (R

Business Segment Information (Reportable Segment Information Derived from Internal Management Reporting Systems, on Basis of Japanese GAAP) (Detail) - JPY (¥) ¥ in Billions		6 Months Ended
		Sep. 30, 2020	Sep. 30, 2019
Japan Gaap Schedule of Segment Reporting Information, by Segment [Line Items]
Gross profits + Net gains (losses) related to ETFs and others	[1]	¥ 1,093.3	¥ 1,022.8	[2]
General and administrative expenses	[3]	679.3	688.4	[2]
Equity in earnings (losses) of equity method investees—net		11.5	19	[2]
Amortization of goodwill and others		6.1	6.6	[2]
Others	[2]		(5.9)
Net business profits (losses) + Net gains (losses) related to ETFs and others	[4]	419.4	340.9	[2]
Fixed assets	[5]	1,721.3	1,701.6	[2]
Operating Segments | Retail And Business Banking Company
Japan Gaap Schedule of Segment Reporting Information, by Segment [Line Items]
Gross profits + Net gains (losses) related to ETFs and others	[1]	307.4	322	[2]
General and administrative expenses	[3]	315	330.7	[2]
Equity in earnings (losses) of equity method investees—net		3.6	6.4	[2]
Amortization of goodwill and others		1.1	1.4	[2]
Net business profits (losses) + Net gains (losses) related to ETFs and others	[4]	(5.1)	(3.7)	[2]
Fixed assets	[5]	518.5	508.2	[2]
Operating Segments | Corporate And Institutional Company
Japan Gaap Schedule of Segment Reporting Information, by Segment [Line Items]
Gross profits + Net gains (losses) related to ETFs and others	[1]	234.2	220.2	[2]
General and administrative expenses	[3]	104.6	104	[2]
Equity in earnings (losses) of equity method investees—net		2.4	1.1	[2]
Amortization of goodwill and others		0.1	0.1	[2]
Net business profits (losses) + Net gains (losses) related to ETFs and others	[4]	131.9	117.2	[2]
Fixed assets	[5]	186.3	208.4	[2]
Operating Segments | Global Corporate Company
Japan Gaap Schedule of Segment Reporting Information, by Segment [Line Items]
Gross profits + Net gains (losses) related to ETFs and others	[1]	222.6	203.9	[2]
General and administrative expenses	[3]	121.4	118.6	[2]
Equity in earnings (losses) of equity method investees—net		5.8	6	[2]
Amortization of goodwill and others		0.2	0.2	[2]
Net business profits (losses) + Net gains (losses) related to ETFs and others	[4]	106.8	91.1	[2]
Fixed assets	[5]	157	160.1	[2]
Operating Segments | Global Markets Company
Japan Gaap Schedule of Segment Reporting Information, by Segment [Line Items]
Gross profits + Net gains (losses) related to ETFs and others	[1]	291.5	235	[2]
General and administrative expenses	[3]	105.6	101.4	[2]
Amortization of goodwill and others		0.4	0.5	[2]
Net business profits (losses) + Net gains (losses) related to ETFs and others	[4]	185.5	133.1	[2]
Fixed assets	[5]	90.9	92.8	[2]
Operating Segments | Asset Management Company
Japan Gaap Schedule of Segment Reporting Information, by Segment [Line Items]
Gross profits + Net gains (losses) related to ETFs and others	[1]	23.6	25.5	[2]
General and administrative expenses	[3]	15.7	16.4	[2]
Equity in earnings (losses) of equity method investees—net		0.4	0.5	[2]
Amortization of goodwill and others		3.8	3.9	[2]
Net business profits (losses) + Net gains (losses) related to ETFs and others	[4]	4.5	5.7	[2]
Fixed assets	[5]	0.1	0.1	[2]
Others
Japan Gaap Schedule of Segment Reporting Information, by Segment [Line Items]
Gross profits + Net gains (losses) related to ETFs and others	[1],[6]	14	16.2	[2]
General and administrative expenses	[3],[6]	17	17.3	[2]
Equity in earnings (losses) of equity method investees—net	[6]	(0.7)	5	[2]
Amortization of goodwill and others	[6]	0.5	0.5	[2]
Others	[2],[6]		(5.9)
Net business profits (losses) + Net gains (losses) related to ETFs and others	[4],[6]	(4.2)	(2.5)	[2]
Fixed assets	[5],[6]	¥ 768.5	¥ 732	[2]
[1]	“Gross profits + Net gains (losses) related to ETFs and others” is reported instead of sales reported by general corporations. Gross profits is defined as the sum of net interest income, fiduciary income, net fee and commission income, net trading income and net other operating income. Net gains (losses) related to ETFs and others consist of net gains (losses) on ETFs held by MHBK and MHTB on their non-consolidated basis and net gains (losses) on operating investment securities of MHSC on its consolidated basis. For the six months ended September 30, 2019 and 2020, net gains (losses) related to ETFs and others amounted to ¥(8.0) billion and ¥(19.0) billion, respectively, of which ¥(11.2) billion and ¥(20.4) billion are included in “Global Markets Company,” respectively.
[2]	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.
[3]	“General and administrative expenses” excludes non-allocated gains (losses), net.
[4]	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 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.
[5]	“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.
[6]	“Others” includes the following items: • profits and expenses pertaining to consolidated subsidiaries that are not subject to allocation; • consolidating adjustments, including elimination 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.

Business Segment Information _2

Business Segment Information (Reportable Segment Information Derived from Internal Management Reporting Systems, on Basis of Japanese GAAP) (Parenthetical) (Detail) - JPY (¥) ¥ in Billions		6 Months Ended
		Sep. 30, 2020	Sep. 30, 2019
Japan Gaap Schedule of Segment Reporting Information, by Segment [Line Items]
Gross profits and net gains (losses) related to ETFs and others	[1]	¥ 1,093.3	¥ 1,022.8	[2]
Exchange Traded Funds
Japan Gaap Schedule of Segment Reporting Information, by Segment [Line Items]
Gross profits and net gains (losses) related to ETFs and others		(19)	(8)
Global Markets Company | Exchange Traded Funds
Japan Gaap Schedule of Segment Reporting Information, by Segment [Line Items]
Gross profits and net gains (losses) related to ETFs and others		¥ (20.4)	¥ (11.2)
[1]	“Gross profits + Net gains (losses) related to ETFs and others” is reported instead of sales reported by general corporations. Gross profits is defined as the sum of net interest income, fiduciary income, net fee and commission income, net trading income and net other operating income. Net gains (losses) related to ETFs and others consist of net gains (losses) on ETFs held by MHBK and MHTB on their non-consolidated basis and net gains (losses) on operating investment securities of MHSC on its consolidated basis. For the six months ended September 30, 2019 and 2020, net gains (losses) related to ETFs and others amounted to ¥(8.0) billion and ¥(19.0) billion, respectively, of which ¥(11.2) billion and ¥(20.4) billion are included in “Global Markets Company,” respectively.
[2]	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.

Business Segment Information _3

Business Segment Information (Reconciliation of Total Net Business Profits under Internal Management Reporting Systems to Income Before Income Tax Expense on Consolidated Statements of Income) (Detail) - JPY (¥) ¥ in Millions		6 Months Ended
		Sep. 30, 2020	Sep. 30, 2019
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Net business profits (losses) + Net gains (losses) related to ETFs and others		¥ 419,400	¥ 340,900
Adjustment to reconcile management reporting to Japanese GAAP:
General and administrative expenses: non-allocated gains (losses), net		4,100	24,500
Expenses related to portfolio problems (including reversal of (provision for) general reserve for losses on loans)		(84,800)	(19,100)
Gains on reversal of reserves for possible losses on loans, and others		3,600	7,900
Net gains (losses) related to stocks—Net gains (losses) related to ETFs and others		(50,500)	55,400
Net extraordinary gains (losses)		65,800	(5,000)
Others		(24,200)	(13,100)
Income before income tax expense under Japanese GAAP		333,400	391,500
Adjustment to reconcile Japanese GAAP to U.S. GAAP:
Derivative financial instruments and hedging activities		(12,900)	105,000
Investments		285,400	(163,900)
Loans		(10,800)	0
Allowances for credit losses	[1]	35,800	500
Premises and equipment		(37,100)	(51,500)
Land revaluation		2,700	500
Business combinations		(4,300)	4,100
Pension liabilities		(84,500)	(27,300)
Consolidation of variable interest entities		36,600	40,300
Foreign currency translation		(200)	14,300
Others		3,700	(3,000)
Income before income tax expense		¥ 547,841	¥ 310,456
[1]	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 six months ended September 30, 2020 substitute allowances for loan losses and off-balance-sheet instruments for the six months ended September 30, 2019. See Note 2 “Issued accounting pronouncements” for further details.

Business Segment Information _4

Business Segment Information (Reconciliation of Assets from Segment to Consolidated) (Detail) - JPY (¥) ¥ in Billions		6 Months Ended
		Sep. 30, 2020	Sep. 30, 2019
Schedule Of Assets By Segment [Line Items]
Fixed assets	[1]	¥ 1,721.3	¥ 1,701.6	[2]
U.S. GAAP adjustments	[3]	818.4	964.5
Premises and equipment-net, Goodwill, Intangible assets, and right-of-use assets related to operating leases included in Other assets		¥ 2,539.7	¥ 2,666.1
[1]	“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.
[2]	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.
[3]	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.

Subsequent events - Additional

Subsequent events - Additional Information (Detail) - JPY (¥) ¥ in Billions	Jun. 25, 2020	Sep. 30, 2020
Subsequent Events [Abstract]
Stockholders equity stock consolidation	1-for-10 share
Decrease in defined benefit obligations		¥ 22
Decrease in plan assets		¥ 24