Mizuho Financial (MFG) 6-K 28 Dec 17 2017 H1 Current report (foreign) Financial data

Document and Entity Information

Document and Entity Information	6 Months Ended
	Sep. 30, 2017
Document Type	6-K
Amendment Flag	false
Document Period End Date	Sep. 30, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	H1
Trading Symbol	MFG
Entity Registrant Name	MIZUHO FINANCIAL GROUP INC
Entity Central Index Key	1,335,730
Current Fiscal Year End Date	--03-31

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - JPY (¥) ¥ in Millions	Sep. 30, 2017	Mar. 31, 2017
Assets:
Cash and due from banks	¥ 1,395,268	¥ 1,592,191
Interest-bearing deposits in other banks	50,002,272	45,994,780
Call loans and funds sold	900,137	1,037,986
Receivables under resale agreements (Note 20)	9,408,536	8,967,712
Receivables under securities borrowing transactions (Note 20)	3,585,209	3,350,052
Trading account assets	27,457,300	24,998,493
Investments (Notes 4 and 19):
Available-for-sale securities (including assets pledged that secured parties are permitted to sell or repledge of ¥442,775 million at March 31, 2017 and ¥566,710 million at September 30, 2017)	20,152,046	20,557,118
Held-to-maturity securities (including assets pledged that secured parties are permitted to sell or repledge of ¥1,050,714 million at March 31, 2017 and ¥889,900 million at September 30, 2017)	3,127,486	3,817,360
Other investments	537,072	595,069
Loans (Notes 5, 6 and 19)	83,883,459	82,283,906
Allowance for loan losses	(350,469)	(479,673)
Loans, net of allowance	83,532,990	81,804,233
Premises and equipment-net	2,087,942	2,041,273
Due from customers on acceptances	149,403	184,171
Accrued income	286,330	270,694
Goodwill	95,196	95,176
Intangible assets	89,353	94,147
Deferred tax assets	62,232	63,520
Other	6,108,291	4,992,329
Total	208,977,063	200,456,304
Liabilities and equity:
Noninterest-bearing deposits	19,439,503	19,063,774
Interest-bearing deposits	90,716,677	87,358,504
Noninterest-bearing deposits	2,935,622	1,996,450
Interest-bearing deposits	23,957,970	22,766,225
Due to trust accounts	3,999,356	4,123,088
Call money and funds purchased	1,602,970	1,255,172
Payables under repurchase agreements (Notes 20 and 21)	19,522,038	17,969,941
Payables under securities lending transactions (Notes 20 and 21)	2,873,259	1,919,249
Other short-term borrowings	931,329	1,476,612
Trading account liabilities	12,945,086	13,591,740
Bank acceptances outstanding	149,403	184,171
Income taxes payable	70,301	73,598
Deferred tax liabilities	235,768	140,475
Accrued expenses	208,867	209,309
Long-term debt	14,132,590	14,529,414
Other	6,055,563	5,026,525
Total	199,776,302	191,684,247
Commitments and contingencies (Note 16)
MHFG shareholders' equity:
Common stock (Note 8)-no par value, authorized 48,000,000,000 shares at March 31, 2017 and September 30, 2017, and issued 25,386,307,945 shares at March 31, 2017, and 25,389,644,945 shares at September 30, 2017	5,825,959	5,826,149
Retained earnings	1,196,269	918,894
Accumulated other comprehensive income, net of tax (Note 10)	1,685,847	1,521,163
Less: Treasury stock, at cost-Common stock 19,992,754 shares at March 31, 2017, and 27,171,089 shares at September 30, 2017	(6,475)	(4,849)
Total MHFG shareholders' equity	8,701,600	8,261,357
Noncontrolling interests	499,161	510,700
Total equity	9,200,761	8,772,057
Total liabilities and equity	208,977,063	200,456,304
Consolidated VIEs
Assets:
Cash and due from banks	51,642	96,077
Interest-bearing deposits in other banks	75,453	81,807
Trading account assets	2,237,926	2,099,890
Investments (Notes 4 and 19):
Investments	47,373	46,180
Loans, net of allowance	1,971,454	2,149,321
Other	750,536	772,290
Total	5,134,384	5,245,565
Liabilities and equity:
Other short-term borrowings	27,475	60,575
Trading account liabilities	2,234	7,723
Long-term debt	452,305	431,190
Other	1,210,885	1,147,895
Total	¥ 1,692,899	¥ 1,647,383

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - JPY (¥) ¥ in Millions	Sep. 30, 2017	Mar. 31, 2017
Trading account assets, assets pledged that secured parties are permitted to sell or repledge	¥ 7,706,512	¥ 5,861,942
Available-for-sale securities, assets pledged that secured parties are permitted to sell or repledge	566,710	442,775
Held-to-maturity securities, assets pledged that secured parties are permitted to sell or repledge	889,900	1,050,714
Long-term debt, liabilities accounted for at fair value	¥ 1,943,986	¥ 1,496,488
Common stock, par value	¥ 0	¥ 0
Common stock, authorized	48,000,000,000	48,000,000,000
Common stock, issued	25,389,644,945	25,386,307,945
Treasury stock, shares	27,171,089	19,992,754

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME - JPY (¥) ¥ in Millions	6 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Interest and dividend income:
Loans, including fees	¥ 537,959	¥ 494,309
Investments:
Interest	37,909	41,303
Dividends	41,781	38,348
Trading account assets	99,569	71,746
Call loans and funds sold	2,829	2,550
Receivables under resale agreements and securities borrowing transactions	66,572	38,428
Deposits	52,806	35,383
Total interest and dividend income	839,425	722,067
Interest expense:
Deposits	182,020	116,237
Trading account liabilities	19,371	10,245
Call money and funds purchased	1,855	1,534
Payables under repurchase agreements and securities lending transactions	106,357	50,494
Other short-term borrowings	6,645	4,946
Long-term debt	97,057	85,312
Total interest expense	413,305	268,768
Net interest income	426,120	453,299
Provision (credit) for loan losses (Notes 5 and 6)	(117,962)	569
Net interest income after provision (credit) for loan losses	544,082	452,730
Noninterest income:
Fee and commission income (Note 18)	401,231	392,462
Foreign exchange gains (losses)-net	50,765	57,090
Trading account gains (losses)-net	235,339	206,061
Investment gains (losses)-net (Note 4)	125,489	128,749
Equity in earnings (losses) of equity method investees-net	10,389	16,726
Gains on disposal of premises and equipment	4,567	3,486
Other noninterest income	33,158	42,431
Total noninterest income	860,938	847,005
Noninterest expenses:
Salaries and employee benefits	341,853	326,676
General and administrative expenses	280,176	274,572
Occupancy expenses	96,340	93,958
Fee and commission expenses	98,298	86,574
Provision (credit) for losses on off-balance-sheet instruments	(4,191)	(7,895)
Other noninterest expenses	79,681	68,577
Total noninterest expenses	892,157	842,462
Income before income tax expense	512,863	457,273
Income tax expense (Note 13)	119,333	74,515
Net income	393,530	382,758
Less: Net income attributable to noncontrolling interests	20,981	3,200
Net income attributable to MHFG shareholders	¥ 372,549	¥ 379,558
Earnings per common share (Note 12):
Basic net income per common share	¥ 14.69	¥ 15.06
Diluted net income per common share	¥ 14.68	¥ 14.95

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - JPY (¥) ¥ in Millions	6 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Net income	¥ 393,530	¥ 382,758
Other comprehensive income (loss), net of tax	165,077	(196,229)
Total comprehensive income	558,607	186,529
Less: Total comprehensive income attributable to noncontrolling interests	21,374	2,310
Total comprehensive income attributable to MHFG shareholders	¥ 537,233	¥ 184,219

CONSOLIDATED STATEMENTS OF EQUI

CONSOLIDATED STATEMENTS OF EQUITY - JPY (¥) ¥ in Millions	Total	Preferred stock	Common Stock	Retained Earnings	Accumulated Other Comprehensive Income	Treasury Stock	Parent	Noncontrolling Interest
Balance at beginning of period at Mar. 31, 2016		¥ 98,924	¥ 5,703,144	¥ 746,785	¥ 1,469,308	¥ (3,610)		¥ 168,640
Cumulative effect of change in accounting principles (Note 17) at Mar. 31, 2016				(329)	330			(10,441)
Balance at beginning of period, adjusted at Mar. 31, 2016				746,456	1,469,638			158,199
Issuance of new shares of common stock due to conversion of preferred stock			98,924
Purchases of treasury stock						(1,869)
Conversion to common stock		¥ (98,924)
Issuance of new shares of common stock due to exercise of stock acquisition rights			969
Disposal of treasury stock						380
Effect of other increase (decrease) in consolidated subsidiaries								3,256
Net income attributable to MHFG shareholders	¥ 379,558			379,558
Change during period	(196,229)				(195,339)
Gains (losses) on disposal of treasury stock			(55)
Dividends paid to noncontrolling interests								(1,971)
Dividends declared	(94,828)			(94,828)
Stock-based compensation related to stock option			(1,009)
Net income attributable to noncontrolling interests	(3,200)							3,200
Performance-based stock compensation program			118
Net unrealized gains (losses) on available-for-sale securities attributable to noncontrolling interests								108
Change in ownership interests in consolidated subsidiaries			706
Foreign currency translation adjustments attributable to noncontrolling interests								(1,000)
Pension liability adjustments attributable to noncontrolling interests								2
Cancellation of treasury stock			(1)			1
Balance at end of period at Sep. 30, 2016	8,264,977		5,802,796	1,031,186	1,274,299	(5,098)	¥ 8,103,183	161,794
Balance at beginning of period at Mar. 31, 2017	8,772,057		5,826,149	918,894	1,521,163	(4,849)		510,700
Balance at beginning of period, adjusted at Mar. 31, 2017				918,894	1,521,163			510,700
Purchases of treasury stock						(2,447)
Issuance of new shares of common stock due to exercise of stock acquisition rights			546
Disposal of treasury stock						821
Effect of other increase (decrease) in consolidated subsidiaries								(27,629)
Net income attributable to MHFG shareholders	372,549			372,549
Change during period	165,077				164,684
Gains (losses) on disposal of treasury stock			(43)
Dividends paid to noncontrolling interests								(5,284)
Dividends declared				(95,174)
Stock-based compensation related to stock option			(580)
Net income attributable to noncontrolling interests	(20,981)							20,981
Performance-based stock compensation program			(235)
Net unrealized gains (losses) on available-for-sale securities attributable to noncontrolling interests								743
Change in ownership interests in consolidated subsidiaries			122
Foreign currency translation adjustments attributable to noncontrolling interests								(379)
Pension liability adjustments attributable to noncontrolling interests								29
Balance at end of period at Sep. 30, 2017	¥ 9,200,761		¥ 5,825,959	¥ 1,196,269	¥ 1,685,847	¥ (6,475)	¥ 8,701,600	¥ 499,161

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - JPY (¥) ¥ in Millions	6 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Cash flows from operating activities:
Net income	¥ 393,530	¥ 382,758
Less: Net income attributable to noncontrolling interests	20,981	3,200
Net income attributable to MHFG shareholders	372,549	379,558
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization	90,064	81,650
Provision (credit) for loan losses	(117,962)	569
Investment losses (gains)-net	(125,489)	(128,749)
Equity in losses (earnings) of equity method investees-net	(10,389)	(16,726)
Foreign exchange losses (gains)-net	19,441	(367,495)
Deferred income tax expense (benefit)	20,095	(27,875)
Net change in trading account assets	(1,166,688)	(575,402)
Net change in trading account liabilities	(766,841)	2,358,095
Net change in loans held for sale	(2,970)	(8,892)
Net change in accrued income	(13,400)	13,947
Net change in accrued expenses	(5,735)	(15,230)
Other-net	(814,192)	165,321
Net cash provided by (used in) operating activities	(2,521,517)	1,858,771
Cash flows from investing activities:
Proceeds from sales of investments	16,390,837	18,374,011
Proceeds from maturities of investments	9,274,406	3,307,892
Purchases of investments	(24,412,985)	(17,554,272)
Proceeds from sales of loans	180,179	126,768
Net change in loans	(1,371,811)	(1,598,393)
Net change in interest-bearing deposits in other banks	(3,932,027)	(7,061,266)
Net change in call loans and funds sold, and receivables under resale agreements and securities borrowing transactions	(316,202)	(2,389,471)
Proceeds from sales of premises and equipment	18,524	3,883
Purchases of premises and equipment	(157,322)	(214,606)
Proceeds from sales of investments in subsidiaries (affecting the scope of consolidation)	948
Net cash used in investing activities	(4,325,453)	(7,005,454)
Cash flows from financing activities:
Net change in deposits	5,267,913	5,292,468
Net change in call money and funds purchased, and payables under repurchase agreements and securities lending transactions	2,621,193	672,490
Net change in due to trust accounts	(123,732)	(1,041,808)
Net change in other short-term borrowings	(545,814)	(411,765)
Proceeds from issuance of long-term debt	1,377,698	3,567,497
Repayment of long-term debt	(1,835,014)	(2,688,095)
Proceeds from noncontrolling interests	927	361
Payments to noncontrolling interests	(11,883)
Proceeds from issuance of common stock	3	6
Proceeds from sales of treasury stock		1
Purchases of treasury stock	(1,605)	(1,430)
Dividends paid	(95,139)	(94,782)
Dividends paid to noncontrolling interests	(5,284)	(1,971)
Net cash provided by financing activities	6,649,263	5,292,972
Effect of exchange rate changes on cash and due from banks	784	(60,349)
Net increase (decrease) in cash and due from banks	(196,923)	85,940
Cash and due from banks at beginning of period	1,592,191	1,322,597
Cash and due from banks at end of period	1,395,268	1,408,537
Noncash investing activities:
Investment in capital leases	¥ 1,807	¥ 4,987

Basis of presentation

Basis of presentation	6 Months Ended
	Sep. 30, 2017
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, 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 22 “Business segment information”. The accompanying consolidated financial statements have been prepared in accordance with 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 and certain subsidiaries’ interim financial reporting period ends on June 30. The necessary adjustments have been made to the consolidated financial statements if significant transactions took place during the three-month period. When determining whether to consolidate investee entities, the MHFG Group performed a careful 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 the 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. The amounts of asset management business fee income and expenses for the six months ended September 30, 2016 have been reclassified from Other noninterest income and Other noninterest expenses to Fee and commission income and Fee and commission expenses, respectively, in order to conform to the current year’s presentation. Such reclassifications had no effect on net income or shareholder’s equity. 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, 2017. 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 loan losses, allowance for losses on off-balance-sheet

Recently issued accounting pron

Recently issued accounting pronouncements	6 Months Ended
	Sep. 30, 2017
Recently issued accounting pronouncements	2. Recently issued accounting pronouncements Accounting pronouncements issued but not yet effective In May 2014, the FASB issued ASU No.2014-09, No.2014-09”). No.2015-14, No.2015-14”) No.2014-09 No.2014-09 No.2014-09 No.2014-09 In January 2016, the FASB issued ASU No.2016-01, 825-10)—Recognition No.2016-01”). No.2016-01 In February 2016, the FASB issued ASU No.2016-02, No.2016-02”). right-of-use No.2016-02 In June 2016, the FASB issued ASU No.2016-13, No.2016-13”). available-for-sale No.2016-13 In October 2016, the FASB issued ASU No.2016-16, No.2016-16”). No.2016-16 In January 2017, the FASB issued ASU No.2017-04, No.2017-04”). No. 2017-04 In May 2017, the FASB issued ASU No.2017-09, No.2017-09”). No. 2017-09 In August 2017, the FASB issued ASU No.2017-12, No.2017-12

Business combination

Business combination	6 Months Ended
	Sep. 30, 2017
Business combination	3. Business combination Integration among asset management companies On October 1, 2016, DIAM Co., Ltd. (“DIAM”), Mizuho Trust & Banking Co., Ltd. (“MHTB”), Mizuho Asset Management Co., Ltd. (“MHAM”) and Shinko Asset Management Co., Ltd. (“Shinko Asset Management”) (collectively, the “Integrating Companies”) integrated their asset management functions pursuant to an integration agreement signed on July 13, 2016. The integration was implemented through the following steps: (i) a merger between MHAM as surviving company and Shinko Asset Management as absorbed company; (ii) a company split between MHTB and MHAM (after the merger in (i) above) as successor company whereby rights and obligations attributed to Asset Management Division of MHTB were transferred to MHAM; and (iii) a merger between DIAM as surviving company and MHAM as absorbed company. After the integration, DIAM was renamed Asset Management One Co., Ltd. (“Asset Management One”). As of September 30, 2016, MHAM was a wholly-owned subsidiary of MHFG and DIAM was an equity method affiliate of the MHFG Group which owned 50.0% of the voting equity interests. On October 1, 2016, MHFG exchanged 30.0% of the voting equity interests in MHAM (after the split in (ii) above) for voting equity interests and non-voting Based on the strong commitment of MHFG and Dai-ichi (“Dai-ichi Dai-ichi The following table summarizes the consideration paid for DIAM and the amounts of the acquired assets and assumed liabilities recognized at the acquisition date, as well as the fair value at the acquisition date of the noncontrolling interest in DIAM. There were no material acquisition-related costs that were recognized separately from the acquisition of the assets and the assumption of the liabilities. At October 1, (in millions of yen) Consideration: Equity instruments (1,038,408 common shares of MHAM) 28,842 Fair value of total consideration transferred 28,842 Fair value of equity interests in DIAM held by MHFG before the business combination 72,106 100,948 Recognized amounts of identifiable assets acquired: Cash and due from banks 831 Interest-bearing deposits in other banks 12,873 Trading account assets 266 Investments 12,234 Premises and equipment-net 3,546 Accrued income 7,882 Intangible assets (Note) 53,037 Deferred tax assets 1,003 Other assets 2,208 Recognized amounts of identifiable liabilities assumed: Trading account liabilities 304 Income taxes payable 918 Deferred taxes liabilities 16,238 Accrued expenses 5,392 Other liabilities 3,041 Total identifiable net assets 67,987 Goodwill 76,225 Noncontrolling interest in DIAM 43,264 100,948 Note: Amount represents customer relationships subject to amortization, of which the weighted-average amortization period is 16.9 years. The fair value of the equity interests in DIAM held by MHFG before the business combination (¥72,106 million), the fair value of the 1,038,408 common shares of MHAM as the consideration paid for DIAM (¥28,842 million) and the fair value of the noncontrolling interest in DIAM (¥43,264 million) were determined with reference to an independent third-party appraisal by applying the income approach and the market approach. The income approach was based on the discounted future cash flows of DIAM and MHAM and the market approach was based on market values, earnings and revenues of public companies comparable to DIAM and MHAM. A discount for lack of control was not considered in determining the fair value of the noncontrolling interest, which is entirely held by Dai-Ichi Dai-Ichi On October 1, 2016, the MHFG Group recognized a gain of ¥56,226 million as a result of remeasuring to fair value its 50.0% of the voting equity interests in DIAM held before the business combination. The gain is not included in the Group’s consolidated statement of income for the six months ended September 30, 2016. It is included in Other noninterest income for the fiscal year ended March 31, 2017. In addition, the MHFG Group recognized an increase in Common stock of ¥23,829 million as a result of remeasuring to fair value its 30.0% of the voting equity interests in MHAM held before the business combination due to the change in the voting equity interests in MHAM on October 1, 2016. The revenue and earnings of the MHFG Group would not have differed significantly from those reported in the consolidated statements of income for the six months ended September 30, 2016 if the business combination had occurred as of the beginning of the period.

Investments

Investments	6 Months Ended
	Sep. 30, 2017
Investments	4. Investments Available-for-sale held-to-maturity The amortized cost, gross unrealized gains and losses, and fair value of available-for-sale held-to-maturity Amortized cost Gross unrealized Gross unrealized Fair value (in millions of yen) March 31, 2017 Available-for-sale Debt securities: Japanese government bonds 10,256,512 22,782 16,408 10,262,886 Japanese local government bonds 279,864 4,841 233 284,472 U.S. Treasury bonds and federal agency securities 1,148,389 10 4,578 1,143,821 Other foreign government bonds 933,942 1,246 236 934,952 Agency mortgage-backed securities (1) 832,738 15,500 5,441 842,797 Residential mortgage-backed securities 142,879 1,838 558 144,159 Commercial mortgage-backed securities 223,105 1,092 282 223,915 Japanese corporate bonds and other debt securities (2) 1,958,472 52,046 2,286 2,008,232 Foreign corporate bonds and other debt securities (3) 909,052 3,377 1,643 910,786 Equity securities (marketable) 1,528,808 2,273,883 1,593 3,801,098 Total 18,213,761 2,376,615 33,258 20,557,118 Held-to-maturity Debt securities: Japanese government bonds 3,059,976 37,168 — 3,097,144 Agency mortgage-backed securities (4) 757,384 121 7,931 749,574 Total 3,817,360 37,289 7,931 3,846,718 September 30, 2017 Available-for-sale Debt securities: Japanese government bonds 9,672,831 5,728 20,335 9,658,224 Japanese local government bonds 251,023 3,007 464 253,566 U.S. Treasury bonds and federal agency securities 853,697 153 4,096 849,754 Other foreign government bonds 971,933 1,708 820 972,821 Agency mortgage-backed securities (1) 880,882 13,981 4,313 890,550 Residential mortgage-backed securities 135,814 1,495 512 136,797 Commercial mortgage-backed securities 256,777 1,063 454 257,386 Japanese corporate bonds and other debt securities (2) 1,903,923 47,293 1,550 1,949,666 Foreign corporate bonds and other debt securities (3) 889,383 2,437 1,552 890,268 Equity securities (marketable) 1,675,207 2,619,270 1,463 4,293,014 Total 17,491,470 2,696,135 35,559 20,152,046 Held-to-maturity Debt securities: Japanese government bonds 2,459,938 28,111 — 2,488,049 Agency mortgage-backed securities (4) 667,548 51 7,852 659,747 Total 3,127,486 28,162 7,852 3,147,796 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 ¥708,557 million and ¥134,240 million, respectively, at March 31, 2017, and ¥729,895 million and ¥160,655 million, respectively, at September 30, 2017. 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. (2) Other debt securities presented in this line primarily consist of certificates of deposit (“CDs”), of which the total fair values were ¥155,138 million at March 31, 2017, and ¥146,136 million at September 30, 2017. (3) Other debt securities presented in this line primarily consist of CDs and asset-backed securities (“ABS”), of which the total fair values were ¥258,059 million at March 31, 2017, and ¥290,380 million at September 30, 2017. (4) All Agency mortgage-backed securities presented in this line are Ginnie Mae securities. Contractual maturities The amortized cost and fair value of 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 4,076,063 4,201,851 1,394,917 — 9,672,831 Japanese local government bonds 30,530 115,552 100,844 4,097 251,023 U.S. Treasury bonds and federal agency securities 716,047 — 137,650 — 853,697 Other foreign government bonds 706,741 255,529 9,663 — 971,933 Agency mortgage-backed securities — — — 880,882 880,882 Residential mortgage-backed securities — — — 135,814 135,814 Commercial mortgage-backed securities 7,500 159,599 80,278 9,400 256,777 Japanese corporate bonds and other debt securities 395,022 963,809 351,649 193,443 1,903,923 Foreign corporate bonds and other debt securities 468,526 350,022 67,910 2,925 889,383 Total 6,400,429 6,046,362 2,142,911 1,226,561 15,816,263 Held-to-maturity Debt securities: Japanese government bonds 860,031 1,120,025 479,882 — 2,459,938 Agency mortgage-backed securities — — — 667,548 667,548 Total 860,031 1,120,025 479,882 667,548 3,127,486 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 4,073,609 4,200,457 1,384,158 — 9,658,224 Japanese local government bonds 30,587 116,166 102,671 4,142 253,566 U.S. Treasury bonds and federal agency securities 715,889 — 133,865 — 849,754 Other foreign government bonds 706,840 256,228 9,753 — 972,821 Agency mortgage-backed securities — — — 890,550 890,550 Residential mortgage-backed securities — — — 136,797 136,797 Commercial mortgage-backed securities 7,504 159,771 80,935 9,176 257,386 Japanese corporate bonds and other debt securities 395,270 965,654 353,485 235,257 1,949,666 Foreign corporate bonds and other debt securities 468,546 350,541 68,269 2,912 890,268 Total 6,398,245 6,048,817 2,133,136 1,278,834 15,859,032 Held-to-maturity Debt securities: Japanese government bonds 861,783 1,125,592 500,674 — 2,488,049 Agency mortgage-backed securities — — — 659,747 659,747 Total 861,783 1,125,592 500,674 659,747 3,147,796 Other-than-temporary impairment The MHFG Group performs periodic reviews to identify impaired securities in accordance with ASC 320, “Investments—Debt and Equity Securities” (“ASC 320”). For debt securities, in the cases where the MHFG Group has the intent to sell a debt security or more likely than not will be required to sell a debt security before the recovery of its amortized cost basis, the full amount of an other-than-temporary impairment loss is recognized immediately through earnings. In other cases, the MHFG Group evaluates expected cash flows to be received and determines if a credit loss exists, and if so, the amount of an other-than-temporary impairment related to the credit loss is recognized in earnings, while the remaining decline in fair value is recognized in other comprehensive income, net of applicable taxes. For equity securities, impairment is evaluated considering the length of time and extent to which the fair value has been below cost, the financial condition and near-term prospects of the issuers, as well as the MHFG Group’s ability and intent to hold these investments for a reasonable period of time sufficient for a forecasted recovery of fair value. If an equity security is deemed other-than-temporarily impaired, it shall be written down to fair value, with the full decline recognized in earnings. The following table shows the other-than-temporary impairment losses on available-for-sale held-to-maturity Six months ended September 30, 2016 2017 (in millions of yen) Available-for-sale Debt securities 56 1,000 Equity securities 10,016 2,521 Total 10,072 3,521 For the six months ended September 30, 2017, the other-than-temporary impairment losses on debt securities were attributable to the decline in the fair value of certain Japanese corporate bonds in respect of which the MHFG Group determined credit losses existed. In accordance with ASC 320-10-35-33A 320-10-35-34B, The other-than-temporary impairment losses on equity securities were mainly attributable to the decline in the fair value of certain Japanese equity securities. 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 Gross Fair Gross Fair value Gross (in millions of yen) March 31, 2017 Available-for-sale Debt securities: Japanese government bonds 5,574,649 15,796 95,612 612 5,670,261 16,408 Japanese local government bonds 58,700 233 — — 58,700 233 U.S. Treasury bonds and federal agency securities 1,013,962 4,578 — — 1,013,962 4,578 Other foreign government bonds 334,300 230 8,327 6 342,627 236 Agency mortgage-backed securities (1) 195,887 3,705 42,501 1,736 238,388 5,441 Residential mortgage-backed securities 5,873 3 28,994 555 34,867 558 Commercial mortgage-backed securities 8,314 218 17,634 64 25,948 282 Japanese corporate bonds and other debt securities 470,602 2,062 158,713 224 629,315 2,286 Foreign corporate bonds and other debt securities 202,347 1,353 77,699 290 280,046 1,643 Equity securities (marketable) 30,688 383 4,117 1,210 34,805 1,593 Total 7,895,322 28,561 433,597 4,697 8,328,919 33,258 Held-to-maturity Debt securities: Agency mortgage-backed securities (2) 460,882 3,518 259,466 4,413 720,348 7,931 Total 460,882 3,518 259,466 4,413 720,348 7,931 September 30, 2017 Available-for-sale Debt securities: Japanese government bonds 7,198,653 9,958 1,420,926 10,377 8,619,579 20,335 Japanese local government bonds 89,207 374 7,802 90 97,009 464 U.S. Treasury bonds and federal agency securities 470,397 785 79,294 3,311 549,691 4,096 Other foreign government bonds 551,664 785 72,166 35 623,830 820 Agency mortgage-backed securities (1) 227,245 2,239 77,620 2,074 304,865 4,313 Residential mortgage-backed securities 18,093 43 25,344 469 43,437 512 Commercial mortgage-backed securities 41,379 417 12,292 37 53,671 454 Japanese corporate bonds and other debt securities 572,056 1,174 206,284 376 778,340 1,550 Foreign corporate bonds and other debt securities 228,662 1,233 31,828 319 260,490 1,552 Equity securities (marketable) 14,441 1,031 21,709 432 36,150 1,463 Total 9,411,797 18,039 1,955,265 17,520 11,367,062 35,559 Held-to-maturity Debt securities: Agency mortgage-backed securities (2) 406,351 3,725 224,851 4,127 631,202 7,852 Total 406,351 3,725 224,851 4,127 631,202 7,852 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 ¥104,270 million and ¥134,118 million, respectively, at March 31, 2017, and ¥144,319 million and ¥160,546 million, respectively, at September 30, 2017. 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. (2) All Agency mortgage-backed securities presented in this line are Ginnie Mae securities. At September 30, 2017, 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, U.S. Treasury bonds and federal agency securities 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, including Japanese corporate bonds with similar credit risks as the other-than-temporarily impaired securities, 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, the MHFG Group determined that the debt securities in an unrealized loss position were not considered other-than-temporarily impaired. The equity securities in an unrealized loss position were determined not to be other-than-temporarily impaired based on the evaluation of the following factors: (1) the severity and duration of the impairments, (2) the financial condition and near-term prospects of the issuers, and (3) the MHFG Group’s ability and intent to hold these investments for a reasonable period of time sufficient for a forecasted recovery of fair value. Realized gains and losses The following table shows the realized gains and losses on sales of available-for-sale available-for-sale Six months ended September 30, 2016 2017 (in millions of yen) Gross realized gains 144,796 127,360 Gross realized losses (9,615 ) (10,020 ) Net realized gains (losses) on sales of available-for-sale 135,181 117,340 Other investments The following table summarizes the composition of Other investments at March 31, 2017 and September 30, 2017: March 31, 2017 September 30, 2017 (in millions of yen) Equity method investments 249,679 255,370 Investments held by consolidated investment companies 37,462 38,779 Other equity interests 307,928 242,923 Total 595,069 537,072 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 ¥132,817 million and ¥140,613 million, at March 31, 2017 and September 30, 2017, respectively. The aggregate market values of these marketable equity securities were ¥273,249 million and ¥261,756 million, respectively. The majority of the aggregate market values of these marketable equity securities are related to Orient Corporation, of which the MHFG Group’s proportionate share of the total outstanding common stock was 49.0% as of September 30, 2017. 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 Other equity interests Other equity interests primarily consist of non-marketable

Loans

Loans	6 Months Ended
	Sep. 30, 2017
Loans	5 . Loans The table below presents loans outstanding by domicile and industry of borrower at March 31, 2017 and September 30, 2017: March 31, 2017 September 30, 2017 (in millions of yen) Domestic: Manufacturing 8,740,281 8,526,643 Construction and real estate 7,654,016 7,709,245 Services 4,759,225 4,923,838 Wholesale and retail 5,142,003 5,123,176 Transportation and communications 3,490,415 3,413,710 Banks and other financial institutions 4,006,401 4,247,285 Government and public institutions 8,532,246 9,981,557 Other industries (Note) 4,427,349 4,502,531 Individuals: Mortgage loans 9,964,633 9,702,129 Other 939,971 958,159 Total domestic 57,656,540 59,088,273 Foreign: Commercial and industrial 16,872,448 16,915,590 Banks and other financial institutions 6,759,921 6,897,692 Government and public institutions 959,948 1,088,753 Other (Note) 190,724 37,938 Total foreign 24,783,041 24,939,973 Total 82,439,581 84,028,246 Less: Unearned income and deferred loan fees—net 155,675 144,787 Total loans before allowance for loan losses 82,283,906 83,883,459 Note: Other industries of Domestic and Other of Foreign include trade receivables and lease receivables of consolidated VIEs. Net losses on sales of loans were ¥919 million and ¥3,739 million, including unrealized losses related to recording loans held for sale at the lower of cost or fair value of ¥310 million, and ¥3,707 million for the fiscal year ended March 31, 2017 and for the six months ended September 30, 2017, 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 and pool allocations 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 incurring losses 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 groups of small balance, homogeneous loans. The Group pools loans with similar risk characteristics, and the risk is assessed 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. The table below presents the MHFG Group’s definition of obligor ratings used by Mizuho Bank, Ltd. (“MHBK”) and MHTB: Obligor category 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 (Note) 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. Note: Special attention obligors are watch obligors with debt in troubled debt restructuring (“TDR”) or 90 days or more delinquent debt. Loans to such obligors are considered impaired. The table below presents credit quality information of loans based on the MHFG Group’s internal rating system at March 31, 2017 and September 30, 2017: Normal obligors Watch obligors (1) A-B C-D Retail (2) Other (3) E1-E2 Retail (2) Other (3) Impaired Total (in millions of yen) March 31, 2017 Domestic: Manufacturing 5,313,232 2,599,760 90,825 67,734 276,771 11,589 1,314 379,056 8,740,281 Construction and real estate 4,199,022 2,641,436 558,321 15,585 165,836 16,023 317 57,476 7,654,016 Services 2,699,487 1,687,515 185,577 910 95,973 23,189 204 66,370 4,759,225 Wholesale and retail 2,244,214 2,369,842 200,003 22,785 124,846 32,911 501 146,901 5,142,003 Transportation and communications 2,584,367 739,781 82,543 1,092 50,319 9,698 — 22,615 3,490,415 Banks and other financial institutions 3,050,605 887,527 1,894 37,907 21,574 353 — 6,541 4,006,401 Government and public institutions 4,059,349 1,600 — 4,471,297 — — — — 8,532,246 Other industries (4) 1,873,137 591,109 3,535 1,906,756 4,613 410 41,179 6,610 4,427,349 Individuals — 289,809 10,312,739 80,566 26,288 89,066 1,434 104,702 10,904,604 Total domestic 26,023,413 11,808,379 11,435,437 6,604,632 766,220 183,239 44,949 790,271 57,656,540 Foreign: Commercial and industrial 9,310,432 4,814,906 173 2,153,757 312,275 — 90,722 190,183 16,872,448 Banks and other financial institutions 5,628,387 592,380 — 480,806 58,348 — — — 6,759,921 Government and public institutions 741,478 214,558 — 1,082 2,801 — — 29 959,948 Other (4) — 6,535 9,439 173,464 124 8 753 401 190,724 Total foreign 15,680,297 5,628,379 9,612 2,809,109 373,548 8 91,475 190,613 24,783,041 Total 41,703,710 17,436,758 11,445,049 9,413,741 1,139,768 183,247 136,424 980,884 82,439,581 September 30, 2017 Domestic: Manufacturing 5,302,937 2,718,865 85,978 46,881 225,293 10,880 239 135,570 8,526,643 Construction and real estate 4,341,519 2,583,327 533,436 8,471 174,429 16,592 — 51,471 7,709,245 Services 2,802,307 1,647,922 181,122 125,114 89,500 21,722 — 56,151 4,923,838 Wholesale and retail 2,241,712 2,395,149 190,225 13,830 110,009 31,369 669 140,213 5,123,176 Transportation and communications 2,511,302 753,838 79,972 1,948 30,502 9,275 — 26,873 3,413,710 Banks and other financial institutions 3,462,891 592,365 1,774 160,314 22,659 220 — 7,062 4,247,285 Government and public institutions 3,237,595 1,600 — 6,742,362 — — — — 9,981,557 Other industries (4) 2,376,483 188,887 3,634 1,918,680 2,368 289 8,927 3,263 4,502,531 Individuals — 300,201 10,081,604 69,829 25,766 84,265 1,275 97,348 10,660,288 Total domestic 26,276,746 11,182,154 11,157,745 9,087,429 680,526 174,612 11,110 517,951 59,088,273 Foreign: Commercial and industrial 9,442,125 4,635,302 206 2,221,178 383,128 — 79,905 153,746 16,915,590 Banks and other financial institutions 5,867,251 563,445 — 411,234 54,835 — 927 — 6,897,692 Government and public institutions 865,441 220,632 — 861 1,800 — — 19 1,088,753 Other (4) — 4,800 9,044 21,800 246 7 1,284 757 37,938 Total foreign 16,174,817 5,424,179 9,250 2,655,073 440,009 7 82,116 154,522 24,939,973 Total 42,451,563 16,606,333 11,166,995 11,742,502 1,120,535 174,619 93,226 672,473 84,028,246 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 impaired. (2) Amounts represent small balance, homogeneous loans which are subject to pool allocations. (3) Non-impaired (4) Other industries of Domestic and Other of Foreign include trade receivables and lease receivables of consolidated VIEs. Impaired loans Loans are considered impaired 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 impaired 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 impaired loans. Impaired 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, “Receivables” (“ASC 310”). 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 impaired loans. All of the MHFG Group’s impaired loans are designated as nonaccrual loans and thus 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 uncertain, otherwise, as interest income. Loans are not restored to accrual status until interest and principal payments are current and future payments are reasonably assured. Impaired loans are restored to non-impaired non-impaired Recorded investment (1) Requiring Not (2) Total Unpaid Related (3) Average Interest ( 4 ) (in millions of yen) March 31, 2017 Domestic: Manufacturing 372,241 6,815 379,056 383,812 148,777 375,895 2,859 Construction and real estate 46,130 11,346 57,476 66,006 6,367 66,796 877 Services 58,366 8,004 66,370 72,261 20,122 66,050 1,173 Wholesale and retail 133,466 13,435 146,901 155,023 52,341 148,865 2,261 Transportation and communications 19,386 3,229 22,615 23,568 5,968 24,035 371 Banks and other financial 2,601 3,940 6,541 6,873 962 5,305 50 Other industries 6,484 126 6,610 6,740 1,999 6,053 91 Individuals 51,893 52,809 104,702 114,880 4,935 114,104 1,696 Total domestic 690,567 99,704 790,271 829,163 241,471 807,103 9,378 Foreign: Total foreign 160,563 30,050 190,613 209,129 61,102 169,192 2,040 Total 851,130 129,754 980,884 1,038,292 302,573 976,295 11,418 Recorded investment (1) Requiring Not (2) Total Unpaid Related (3) Average Interest ( 4 ) (in millions of yen) September 30, 2017 Domestic: Manufacturing 130,184 5,386 135,570 140,010 48,786 257,313 914 Construction and real estate 41,808 9,663 51,471 59,519 5,397 54,473 338 Services 46,498 9,653 56,151 63,777 12,280 61,260 432 Wholesale and retail 129,030 11,183 140,213 148,775 49,871 143,557 1,031 Transportation and communications 24,139 2,734 26,873 27,865 7,134 24,744 160 Banks and other financial institutions 3,100 3,962 7,062 7,395 1,433 6,802 29 Other industries 2,184 1,079 3,263 3,393 1,534 4,937 17 Individuals 46,492 50,856 97,348 102,916 4,657 101,025 729 Total domestic 423,435 94,516 517,951 553,650 131,092 654,111 3,650 Foreign: Total foreign 127,433 27,089 154,522 172,523 48,620 172,567 1,069 Total 550,868 121,605 672,473 726,173 179,712 826,678 4,719 Notes: (1) Amounts represent the outstanding balances of nonaccrual loans. The MHFG Group’s policy for placing loans in nonaccrual status corresponds to the Group’s definition of impaired loans. (2) These impaired loans do not require an allowance for loan losses because the MHFG Group has sufficient collateral to cover probable loan losses. (3) The allowance for loan losses on impaired loans includes the allowance for groups of small balance, homogeneous loans which were collectively evaluated for impairment, in addition to the allowance for those loans that were individually evaluated for impairment. The total carrying amount of the groups of small balance, homogeneous loans at March 31, 2017 and September 30, 2017 was ¥302,251 million and ¥266,915 million, respectively. (4) Amounts represent gross interest income on impaired loans which were included in Interest income on loans in the consolidated statements of income. The remaining balance of impaired loans which had been partially charged off was ¥26,513 million and ¥19,275 million as of March 31, 2017 and September 30, 2017, respectively. Troubled debt restructurings The MHFG Group considers a TDR to be a restructuring in which it, for economic or legal reasons related to the obligor’s financial difficulties, grants a concession to the obligor that it would not otherwise consider. The Group considers the relevant obligor to be in financial difficulty when its obligor rating is E2 or below. The following table presents TDRs that were entered into during the six months ended September 30, 2016 and 2017: Loan forgiveness or debt to equity swaps Interest rate reduction Recorded investment (Note) Charge-offs (in millions of yen) September 30, 2016 Domestic: Manufacturing — — 54,476 Construction and real estate — — 8,596 Services — — 21,951 Wholesale and retail — — 87,237 Transportation and communications — — 8,656 Banks and other financial institutions — — 3,198 Other industries — — 2,274 Individuals — — 9,205 Total domestic — — 195,593 Foreign: Total foreign — — 10,849 Total — — 206,442 September 30, 2017 Domestic: Manufacturing — — 55,611 Construction and real estate — — 9,045 Services — — 18,740 Wholesale and retail — — 74,625 Transportation and communications — — 12,244 Banks and other financial institutions — — 3,461 Individuals — — 7,619 Total domestic — — 181,345 Foreign: Total foreign — — 13,303 Total — — 194,648 Note: Amounts represent the book values of loans immediately after the restructurings. 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, 2016 and 2017 with respect to the loans modified as TDRs within the previous twelve months: Recorded investment September 30, 2016 September 30, 2017 (in millions of yen) Domestic: Manufacturing 1,801 2,006 Construction and real estate 1,621 70 Services 1,188 2,561 Wholesale and retail 4,614 13,396 Transportation and communications 771 201 Other industries — 130 Individuals 1,366 904 Total domestic 11,361 19,268 Foreign: Total foreign 30 4,588 Total 11,391 23,856 Age analysis of past due loans The table below presents an analysis of the age of the recorded investment in loans that are past due at March 31, 2017 and September 30, 2017: 30-59 days 60-89 days 90 days or Total past Current Total (in millions of yen) March 31, 2017 Domestic: Manufacturing 1,938 360 7,767 10,065 8,730,216 8,740,281 Construction and real estate 2,818 947 32,523 36,288 7,617,728 7,654,016 Services 917 217 5,914 7,048 4,752,177 4,759,225 Wholesale and retail 1,330 2,834 5,585 9,749 5,132,254 5,142,003 Transportation and communications 384 322 1,859 2,565 3,487,850 3,490,415 Banks and other financial institutions — — — — 4,006,401 4,006,401 Government and public institutions — — — — 8,532,246 8,532,246 Other industries — — 69 69 4,427,280 4,427,349 Individuals 32,995 12,291 34,846 80,132 10,824,472 10,904,604 Total domestic 40,382 16,971 88,563 145,916 57,510,624 57,656,540 Foreign: Total foreign 546 216 95,719 96,481 24,686,560 24,783,041 Total 40,928 17,187 184,282 242,397 82,197,184 82,439,581 September 30, 2017 Domestic: Manufacturing 1,504 289 8,545 10,338 8,516,305 8,526,643 Construction and real estate 1,006 940 27,869 29,815 7,679,430 7,709,245 Services 2,076 1,537 4,898 8,511 4,915,327 4,923,838 Wholesale and retail 1,842 997 3,803 6,642 5,116,534 5,123,176 Transportation and communications 76 85 7,502 7,663 3,406,047 3,413,710 Banks and other financial institutions — — — — 4,247,285 4,247,285 Government and public institutions — — — — 9,981,557 9,981,557 Other industries 40 — 25 65 4,502,466 4,502,531 Individuals 31,787 11,185 34,554 77,526 10,582,762 10,660,288 Total domestic 38,331 15,033 87,196 140,560 58,947,713 59,088,273 Foreign: Total foreign 848 462 73,898 75,208 24,864,765 24,939,973 Total 39,179 15,495 161,094 215,768 83,812,478 84,028,246 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 ¥26,689 million and ¥20,546 million at March 31, 2017 and September 30, 2017, respectively.

Allowance for loan losses

Allowance for loan losses	6 Months Ended
	Sep. 30, 2017
Allowance for loan losses	6. Allowance for loan losses The MHFG Group maintains an appropriate allowance for loan losses to absorb probable losses inherent in the loan portfolio and makes adjustments to such allowance through Provision (credit) for loan losses in the consolidated statements of income. 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 loan losses. In general, the MHFG Group charges off loans when the Group determines that the obligor should be classified as substantially bankrupt or bankrupt. See Note 5 “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 other obligors, the Group separately monitors the credit quality of each obligor without using time-based triggers. Subsequent recoveries of previously charged-off The credit quality review process and the credit rating process serve as the basis for determining the allowance for loan losses. 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. In determining the appropriate level of the allowance, the MHFG Group evaluates the probable loss by category of loan based on its risk type and characteristics. The allowance for loan losses is determined in accordance with ASC 310 and ASC 450, “Contingencies” (“ASC 450”). The MHFG Group measures the impairment of a loan when it is probable that the Group will be unable to collect all amounts due according to the contractual terms of the loan agreement, 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 Group obtains for loans consists primarily of real estate or listed securities. 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 MHBK and MHTB, when management estimates probable credit losses to determine the allowance for loan losses, small balance, homogeneous loans are classified in the retail portfolio segment to which pool allocations apply, and loans other than these classified in the retail portfolio segment are classified in the corporate portfolio segment. The corporate portfolio segment consists of loans originated 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 retail portfolio segment consists mainly of residential mortgage loans, originated by MHBK. The other portfolio segment consists of loans of subsidiaries other than MHBK and MHTB, such as consolidated VIEs and overseas subsidiaries. The formula allowance is applied to groups of small balance, homogeneous loans that are collectively evaluated for impairment and to non-homogeneous The historical loss rate is adjusted, where appropriate, to reflect current factors, such as general economic and business conditions affecting the key lending areas of the MHFG Group, credit quality trends, specific industry conditions within portfolio segments, and recent loss experience in particular segments of the portfolio. When determining the length of the period to calculate the probability of default, the Group considers the uncertainty in the economic and business conditions. The estimation of the formula allowance is back-tested on a periodic basis by comparing the allowance with the actual results subsequent to the balance sheet date. Changes in Allowance for loan losses by portfolio segment for the six months ended September 30, 2016 and 2017 are shown below: Corporate Retail Other Total (in millions of yen) Six months ended September 30, 2016 Balance at beginning of period 367,739 44,221 39,287 451,247 Provision (credit) for loan losses 9,123 (7,983 ) (571 ) 569 Charge-offs (10,332 ) (1,016 ) (3,812 ) (15,160 ) Recoveries 8,877 4,725 2,139 15,741 Net charge-offs (1,455 ) 3,709 (1,673 ) 581 Others (Note) (10,404 ) — (4,813 ) (15,217 ) Balance at end of period 365,003 39,947 32,230 437,180 Six months ended September 30, 2017 Balance at beginning of period 407,327 36,923 35,423 479,673 Provision (credit) for loan losses (109,379 ) (6,469 ) (2,114 ) (117,962 ) Charge-offs (17,366 ) (745 ) (3,107 ) (21,218 ) Recoveries 6,447 315 1,247 8,009 Net charge-offs (10,919 ) (430 ) (1,860 ) (13,209 ) Others (Note) 2,552 — (585 ) 1,967 Balance at end of period 289,581 30,024 30,864 350,469 Note: Others includes primarily foreign exchange translation. The table below presents Allowance for loan losses and loans outstanding by portfolio segment disaggregated on the basis of impairment method at March 31, 2017 and September 30, 2017: Corporate Retail Other Total (in millions of yen) March 31, 2017 Allowance for loan losses 407,327 36,923 35,423 479,673 of which individually evaluated for impairment 272,714 2,922 13,306 288,942 of which collectively evaluated for impairment 134,613 34,001 22,117 190,731 Loans (Note) 61,120,654 11,722,726 9,596,201 82,439,581 of which individually evaluated for impairment 772,647 23,422 65,075 861,144 of which collectively evaluated for impairment 60,348,007 11,699,304 9,531,126 81,578,437 September 30, 2017 Allowance for loan losses 289,581 30,024 30,864 350,469 of which individually evaluated for impairment 170,509 2,761 7,248 180,518 of which collectively evaluated for impairment 119,072 27,263 23,616 169,951 Loans (Note) 60,727,073 11,432,376 11,868,797 84,028,246 of which individually evaluated for impairment 673,081 22,734 61,318 757,133 of which collectively evaluated for impairment 60,053,992 11,409,642 11,807,479 83,271,113 Note: Amounts represent loan balances before deducting unearned income and deferred loan fees.

Other assets and liabilities

Other assets and liabilities	6 Months Ended
	Sep. 30, 2017
Other assets and liabilities	7. Other assets and liabilities The following table sets forth the details of other assets and liabilities at March 31, 2017 and September 30, 2017: March 31, 2017 September 30, 2017 (in millions of yen) Other assets: Accounts receivable from brokers, dealers and customers for securities transactions 1,564,295 2,000,669 Collateral provided for derivative transactions 973,404 1,110,240 Prepaid pension cost 682,592 707,464 Margins provided for futures contracts 276,398 363,325 Miscellaneous receivables 324,135 294,262 Security deposits 122,858 127,302 Loans held for sale 26,689 20,546 Other 1,021,958 1,484,483 Total 4,992,329 6,108,291 Other liabilities: Accounts payable to brokers, dealers and customers for securities transactions 1,400,141 2,710,819 Guaranteed trust principal 683,324 714,801 Collateral accepted for derivative transactions 671,691 568,881 Miscellaneous payables 481,809 456,138 Margins accepted for futures contracts 307,066 363,221 Unearned income 134,666 130,480 Factoring amounts owed to customers 53,488 22,810 Other 1,294,340 1,088,413 Total 5,026,525 6,055,563 Guaranteed trust principal Guaranteed trust principal is the liability of certain consolidated trust arrangements, in respect of which the MHFG Group provides guarantees for the repayment of principal. See Note 17 “Variable interest entities and securitizations” for further discussion of the guaranteed principal money trusts. Unearned income Unearned income is primarily comprised of refundable fees received from consumer loan customers at the time the loan was made, which is being deferred and recognized in earnings as earned.

Preferred and common stock

Preferred and common stock	6 Months Ended
	Sep. 30, 2017
Preferred and common stock	8. Preferred and common stock Preferred stock The composition of preferred stock at March 31, 2017 and September 30, 2017 is as follows: Class of stock March 31, 2017 September 30, 2017 Authorized Issued Authorized Issued (number of shares) Class XI preferred stock 914,752,000 — — — First series class XIV preferred stock (1) 900,000,000 — 900,000,000 — Second series class XIV preferred stock (1) 900,000,000 — 900,000,000 — Third series class XIV preferred stock (1) 900,000,000 — 900,000,000 — Fourth series class XIV preferred stock (1) 900,000,000 — 900,000,000 — First series class XV preferred stock (2) 900,000,000 — 900,000,000 — Second series class XV preferred stock (2) 900,000,000 — 900,000,000 — Third series class XV preferred stock (2) 900,000,000 — 900,000,000 — Fourth series class XV preferred stock (2) 900,000,000 — 900,000,000 — First series class XVI preferred stock (3) 1,500,000,000 — 1,500,000,000 — Second series class XVI preferred stock (3) 1,500,000,000 — 1,500,000,000 — Third series class XVI preferred stock (3) 1,500,000,000 — 1,500,000,000 — Fourth series class XVI preferred stock (3) 1,500,000,000 — 1,500,000,000 — Total 4,214,752,000 — 3,300,000,000 — Notes: (1) The total number of authorized shares from first to fourth series class XIV preferred stock shall not exceed 900,000,000. (2) The total number of authorized shares from first to fourth series class XV preferred stock shall not exceed 900,000,000. (3) The total number of authorized shares from first to fourth series class XVI preferred stock shall not exceed 1,500,000,000. Common stock The number of issued shares of common stock at March 31, 2017 and September 30, 2017 was 25,386,307,945 shares and 25,389,644,945 shares, respectively. The increase of 3,337,000 shares was due to exercise of stock acquisition rights.

Dividends

Dividends	6 Months Ended
	Sep. 30, 2017
Dividends	9 . Dividends The following table shows dividends on preferred stock and common stock during the six months ended September 30, 2016 and 2017: September 30, 2016 Cash dividends Class of stock Per share In aggregate (in yen) (in millions of yen) Eleventh series class XI preferred stock 10 989 Common stock 3.75 93,839 Total 94,828 September 30, 2017 Cash dividends Class of stock Per share In aggregate (in yen) (in millions of yen) Common stock 3.75 95,174

Accumulated other comprehensive

Accumulated other comprehensive income	6 Months Ended
	Sep. 30, 2017
Accumulated other comprehensive income	10 . Accumulated other comprehensive income Changes in each component of Accumulated other comprehensive income, net of tax (“AOCI”) for the six months ended September 30, 2016 and 2017 are as follows: Six months ended September 30, 2016 2017 (in millions of yen) AOCI, balance at beginning of period, previously reported 1,469,308 1,521,163 Cumulative effect of change in accounting principles (Note 17) 330 — AOCI, balance at beginning of period, adjusted 1,469,638 1,521,163 Net unrealized gains (losses) on available-for-sale Balance at beginning of period, previously reported 1,409,459 1,461,302 Cumulative effect of change in accounting principles (Note 17) (85 ) — Balance at beginning of period, adjusted 1,409,374 1,461,302 Unrealized holding gains (losses) during period (49,362 ) 247,493 Less: reclassification adjustments for losses (gains) included in net income (86,761 ) (78,659 ) Change during period (136,123 ) 168,834 Balance at end of period 1,273,251 1,630,136 Foreign currency translation adjustments: Balance at beginning of period, previously reported 6,310 (5,535 ) Cumulative effect of change in accounting principles (Note 17) 415 — Balance at beginning of period, adjusted 6,725 (5,535 ) Foreign currency translation adjustments during period (59,893 ) (4,322 ) Less: reclassification adjustments for losses (gains) included in net income — — Change during period (59,893 ) (4,322 ) Balance at end of period (53,168 ) (9,857 ) Pension liability adjustments: Balance at beginning of period 53,539 65,396 Unrealized gains (losses) during period 533 32 Less: reclassification adjustments for losses (gains) included in net income 144 140 Change during period 677 172 Balance at end of period 54,216 65,568 Total other comprehensive income (loss), net of tax attributable to MHFG shareholders (195,339 ) 164,684 AOCI, balance at end of period 1,274,299 1,685,847 The following table shows the amounts reclassified out of AOCI into net income during the six months ended September 30, 2017: Six months ended September 30, 2017 Before tax (1) Tax effect (2) Net of tax before Net of tax attributable to (2) Net of tax attributable to shareholders (in millions of yen) Amounts reclassified out of AOCI into net income: Affected line items in the consolidated statements of income: Net unrealized gains (losses) on available-for-sale 113,819 (35,053 ) 78,766 (107 ) 78,659 Investment gains (losses)—net Pension liability adjustments (233 ) 96 (137 ) (3 ) (140 ) Salaries and employee benefits Total 113,586 (34,957 ) 78,629 (110 ) 78,519 Notes: (1) The amounts in the Before tax column are recorded in each account presented under the heading “Affected line items in the consolidated statements of income”. (2) The amounts in the Tax effect column and Net of tax attributable to noncontrolling interests column are recorded in Income tax expense and Net income (loss) attributable to noncontrolling interests in the consolidated statements of income, respectively.

Regulatory matters

Regulatory matters	6 Months Ended
	Sep. 30, 2017
Regulatory matters	1 1. 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 the Banking Act and related regulations. Capital adequacy ratios of MHFG, MHBK, and MHTB as of March 31, 2017 and September 30, 2017 calculated in accordance with Japanese GAAP and the guidelines established by the Financial Services Agency are set forth in the following table: March 31, 2017 September 30, 2017 Amount Ratio Amount Ratio (in billions of yen, except percentages) Consolidated: MHFG: Common Equity Tier 1 capital: Required (Note) 3,857 6.25 3,856 6.25 Actual 7,002 11.34 7,281 11.80 Tier 1 capital: Required (Note) 4,783 7.75 4,781 7.75 Actual 8,212 13.30 9,005 14.59 Total risk-based capital: Required (Note) 6,017 9.75 6,015 9.75 Actual 10,051 16.28 10,947 17.74 MHBK: Common Equity Tier 1 capital: Required 2,541 4.50 2,525 4.50 Actual 6,304 11.16 6,604 11.76 Tier 1 capital: Required 3,388 6.00 3,366 6.00 Actual 7,536 13.34 8,349 14.87 Total risk-based capital: Required 4,517 8.00 4,489 8.00 Actual 9,149 16.20 10,193 18.16 MHTB: Common Equity Tier 1 capital: Required 112 4.50 110 4.50 Actual 466 18.73 487 19.95 Tier 1 capital: Required 149 6.00 146 6.00 Actual 466 18.73 487 19.95 Total risk-based capital: Required 199 8.00 195 8.00 Actual 485 19.47 505 20.68 Non-consolidated: MHBK: Common Equity Tier 1 capital: Required 2,432 4.50 2,417 4.50 Actual 6,057 11.20 6,347 11.81 Tier 1 capital: Required 3,243 6.00 3,223 6.00 Actual 7,316 13.53 8,101 15.08 Total risk-based capital: Required 4,324 8.00 4,298 8.00 Actual 8,938 16.53 9,949 18.52 MHTB: Common Equity Tier 1 capital: Required 113 4.50 110 4.50 Actual 475 18.98 494 20.28 Tier 1 capital: Required 150 6.00 146 6.00 Actual 475 18.98 494 20.28 Total risk-based capital: Required 200 8.00 195 8.00 Actual 493 19.70 511 20.99 Note: The required ratios disclosed above, at March 31, 2017 and September 30, 2017, include the transitional capital conservation buffer of 1.25% and the transitional additional loss absorbency requirements for global systemically important banks (“G-SIBs”) (“D-SIBs”) MHFG’s securities subsidiaries in Japan are also subject to the capital adequacy requirement under the Financial Instruments and Exchange Act. Failure to maintain a minimum capital ratio will trigger mandatory regulatory actions. Management believes, as of September 30, 2017, that MHFG, MHBK, MHTB, and their securities subsidiaries in Japan 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, 2017
Earnings per common share	1 2. 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 and convertible preferred stock. The following table sets forth the computation of basic and diluted earnings per common share for the six months ended September 30, 2016 and 2017: Six months ended 2016 2017 (in millions of yen) Net income: Net income attributable to MHFG shareholders 379,558 372,549 Less: Net income attributable to preferred shareholders — — Net income attributable to common shareholders 379,558 372,549 Effect of dilutive securities: Convertible preferred stock — — Net income attributable to common shareholders after assumed conversions 379,558 372,549 Six months ended 2016 2017 (thousands of shares) Shares: Weighted average common shares outstanding 25,204,801 25,366,347 Effect of dilutive securities: Convertible preferred stock (Note) 165,533 — Stock options 11,997 7,933 Weighted average common shares after assumed conversions 25,382,331 25,374,280 Six months ended 2016 2017 (in yen) Amounts per common share: Basic net income per common share 15.06 14.69 Diluted net income per common share 14.95 14.68 Note: The number of common shares after assumed conversion of the convertible preferred stock is based on the applicable conversion prices.

Income taxes

Income taxes	6 Months Ended
	Sep. 30, 2017
Income taxes	13. Income taxes The following table presents the components of Income tax expense for the six months ended September 30, 2016 and 2017: Six months ended September 30, 2016 2017 (in millions of yen) Current tax expense 102,390 99,238 Deferred tax expense (benefit) (27,875 ) 20,095 Total income tax expense 74,515 119,333 The preceding table does not reflect the tax effects of items recorded directly in Equity for the six months ended September 30, 2016 and 2017. The detailed amounts recorded directly in Equity are as follows: Six months ended September 30, 2016 2017 (in millions of yen) Net unrealized gains (losses) on available-for-sale Unrealized gains (losses) (21,562 ) 105,819 Less: reclassification adjustments (38,351 ) (35,053 ) Total (59,913 ) 70,766 Foreign currency translation adjustments: Unrealized gains (losses) (126 ) — Less: reclassification adjustments — — Total (126 ) — Pension liability adjustments: Unrealized gains (losses) 239 11 Less: reclassification adjustments 87 96 Total 326 107 Total tax effect before allocation to noncontrolling interests (59,713 ) 70,873 The statutory tax rates were both 30.86% as of September 30, 2016 and 2017. The effective tax rates, 16.30% and 23.27% for the six months ended September 30, 2016 and 2017, respectively, differed from the statutory tax rates. The significant difference of the tax rates for the six months ended September 30, 2016 resulted mainly from the reversal of an outside basis difference related to foreign subsidiaries due to their organizational restructuring and was partially offset by an increase in the valuation allowance. The difference of the tax rates for the six months ended September 30, 2017 consisted of numbers of tax beneficial items including a decrease in valuation allowance related to the MHFG’s foreign subsidiaries in the United States and a change in deferred tax liabilities related to undistributed earnings of subsidiaries. At September 30, 2017, the MHFG Group had net operating loss carryforwards totaling ¥1,602 billion, of which ¥861 billion expires by March 31, 2018, and the remaining amount expires in 2023 and thereafter. The total amount of unrecognized tax benefits was ¥1,992 million at September 30, 2017, 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, 2017 was resolved in the six months period ended September 30, 2017, of which the amount was immaterial. The amount of additional unrecognized tax benefits for the period related to the tax positions taken was also immaterial. The MHFG Group does not anticipate that increases or decreases of unrecognized tax benefits within the next twelve months would have a material effect on its consolidated results of operations or financial condition.

Pension and other employee bene

Pension and other employee benefit plans	6 Months Ended
	Sep. 30, 2017
Pension and other employee benefit plans	1 4. 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, 2016 and 2017: Six months ended September 30, 2016 2017 (in millions of yen) Service cost-benefits earned during the period 22,219 21,643 Interest costs on projected benefit obligations 2,716 3,609 Expected return on plan assets (17,860 ) (17,353 ) Amortization of prior service benefits (97 ) 102 Amortization of net actuarial loss (gain) 385 214 Special termination benefits 1,744 2,128 Net periodic benefit cost 9,107 10,343 As previously disclosed in the consolidated financial statements for the fiscal year ended March 31, 2017, the total contribution of approximately ¥51 billion is expected to be paid to the pension plans during the fiscal year ending March 31, 2018. For the six months ended September 30, 2017, the total contribution of ¥25 billion has been paid to the pension plans. The additional contribution of ¥26 billion is expected to be paid during the remainder of the fiscal year ending March 31, 2018 for a total of ¥51 billion.

Derivative financial instrument

Derivative financial instruments	6 Months Ended
	Sep. 30, 2017
Derivative financial instruments	15. Derivative financial instruments The MHFG Group enters into derivative financial instruments in response to the diverse needs of customers, to control the risk related to the assets and liabilities of the MHFG Group, as part of its asset and liability management, and for proprietary trading purposes. The MHFG 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 MHFG Group is exposed to credit risk associated with counterparty default or nonperformance in respect of transactions. 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 credit risk is measured by the fair value of all derivatives in a gain position and its potential increase at the balance sheet dates. The exposure to 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, 2017 and September 30, 2017. The fair values of derivatives are presented on a gross basis and 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, 2017 Notional amount (1) Designated Not designated Designated Not designated (in billions of yen) Interest rate contracts 961,518 — 8,506 — 8,473 Foreign exchange contracts 167,698 2 2,743 — 2,611 Equity-related contracts 4,177 — 134 5 224 Credit-related contracts 3,696 — 35 — 36 Other contracts 360 — 23 — 22 Total 1,137,449 2 11,441 5 11,366 Fair value Derivative receivables (2) Derivative payables (2) September 30, 2017 Notional amount (1) Designated Not designated Designated Not designated (in billions of yen) Interest rate contracts 956,180 — 7,662 — 7,658 Foreign exchange contracts 169,964 — 2,484 5 2,393 Equity-related contracts 5,396 — 151 14 258 Credit-related contracts 3,273 — 29 — 31 Other contracts 388 — 18 — 17 Total 1,135,201 — 10,344 19 10,357 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 ¥973 billion and ¥672 billion at March 31, 2017, and ¥1,110 billion and ¥569 billion at September 30, 2017, 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. Any ineffectiveness must be reported immediately in earnings. The MHFG Group’s hedging activities include fair value and net investment hedges. Fair value hedges The MHFG Group primarily uses forward contracts to modify exposure to changes in the fair value of available-for-sale The following table summarizes gains and losses information related to fair value hedges for the six months ended September 30, 2016 and 2017: Gains (losses) recorded in income Six months ended September 30, 2016 Derivatives Hedged Hedge Net gain (loss) excluded (in millions of yen) Equity-related contracts 6,002 (7,807 ) — (1,805 ) Total 6,002 (7,807 ) — (1,805 ) Gains (losses) recorded in income Six months ended September 30, 2017 Derivatives Hedged Hedge Net gain (loss) excluded (in millions of yen) Equity-related contracts (22,493 ) 20,208 — (2,285 ) Total (22,493 ) 20,208 — (2,285 ) 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, 2016 and 2017: Gains (losses) recorded in income and other comprehensive income (“OCI”) for six months ended September 30, 2016 2017 Effective portion Ineffective portion Effective portion Ineffective portion (in millions of yen) Financial instruments hedging foreign exchange risk 107,528 890 3,487 196 Total 107,528 890 3,487 196 Note: No amount related to the effective portion of net investment hedges was reclassified from Accumulated other comprehensive income to earnings for the six months ended September 30, 2016 and 2017, respectively. Derivative instruments not designated or qualifying as hedges The MHFG Group enters into the following derivative transactions that do not qualify for hedge accounting with a view to implementing risk management hedging strategies: (1) interest-rate swap transactions for the purpose of hedging the interest-rate risks in deposits, loans etc., (2) currency swap transactions for the purpose of hedging the foreign exchange risk of these assets, and (3) credit derivatives for the purpose of hedging 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 gain (loss) 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, 2016 and 2017: Gains (losses) recorded in income 2016 2017 (in millions of yen) Interest rate contracts 80,040 26,648 Foreign exchange contracts 11,173 (4,511 ) Equity-related contracts (1) 11,049 (41,869 ) Credit-related contracts (2) (4,827 ) (3,371 ) Other contracts 564 494 Total 97,999 (22,609 ) Notes: (1) The net gain (loss) excluded from the assessment of the effectiveness of fair value hedges is not included in the above table. (2) Amounts include the net gain (loss) of ¥(5,698) million and ¥(273) million on the credit derivatives hedging the credit risk of loans during the six months ended September 30, 2016 and 2017, 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, 2017 and September 30, 2017: March 31, 2017 September 30, 2017 Notional amount Fair value Notional amount Fair value (in billions of yen) Credit protection written: Investment grade 1,546 21 1,371 23 Non-investment 298 1 202 1 Total 1,844 22 1,573 24 Credit protection purchased 1,994 (23 ) 1,727 (26 ) 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, 2017 and September 30, 2017: Maximum payout/Notional amount March 31, 2017 September 30, 2017 (in billions of yen) One year or less 507 406 After one year through five years 1,020 926 After five years 317 241 Total 1,844 1,573 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, 2017 and September 30, 2017: March 31, 2017 September 30, 2017 (in billions of yen) Aggregate fair value of derivative instruments with credit-risk-related contingent features in net liability positions 698 755 Collateral provided to counterparties in the normal course of business 658 729 Amount required to be posted as collateral or settled immediately if credit-risk-related contingent features were triggered 40 26

Commitments and contingencies

Commitments and contingencies	6 Months Ended
	Sep. 30, 2017
Commitments and contingencies	16. 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, 2017 and September 30, 2017. 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, September 30, (in billions of yen) Performance guarantees 2,243 2,363 Guarantees on loans 278 259 Guarantees on securities 175 174 Other guarantees 1,823 1,933 Guarantees for the repayment of trust principal 730 642 Liabilities of trust accounts 15,177 15,288 Derivative financial instruments 14,415 13,080 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, 2017 and September 30, 2017: March 31, September 30, (in billions of yen) Investment grade 3,477 3,808 Non-investment 1,042 921 Total 4,519 4,729 Note: Investment grade in the internal rating scale generally corresponds to BBB- or above in the external rating scale. 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, 2017 and September 30, 2017: March 31, September 30, (in billions of yen) Commitments to extend credit (Note) 76,678 77,100 Commercial letters of credit 522 622 Total 77,200 77,722 Note: Commitments to extend credit include commitments to invest in securities. Legal proceedings The MHFG Group is involved in normal collection proceedings initiated by the Group and other legal proceedings in the ordinary course of business. The Group’s Indonesian subsidiary acts as the collateral agent for the trustee of bond issuances made by subsidiaries of Asia Pulp & Paper Company Ltd. (“APP”). In that role, the subsidiary is involved in a dispute between the bondholders and such APP subsidiaries in their capacities as the issuers, guarantors and/or pledgors of security for the bonds relating to foreclosure proceedings in respect of the collateral and the subsidiary has been named as a defendant in a lawsuit brought by the obligors under the bonds in Indonesia. The Group’s consolidated financial statements do not include a reserve in relation to this dispute and the Group does not believe that the resolution of this matter will have a significant impact on the consolidated financial condition or results of operations of the Group, although there can be no assurance as to the foregoing.

Variable interest entities and

Variable interest entities and securitizations	6 Months Ended
	Sep. 30, 2017
Variable interest entities and securitizations	17 . 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, and structured finance. 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 comprehensively 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, as of March 31, 2017 and September 30, 2017: Consolidated VIEs Significant March 31, 2017 Consolidated assets Total assets Maximum (in billions of yen) Asset-backed commercial paper/loan programs 2,031 — — Asset-backed securitizations 629 108 11 Investments in securitization products 375 445 154 Investment funds 2,188 3,895 463 Trust arrangements and other 23 — — Total 5,246 4,448 628 Consolidated VIEs Significant September 30, 2017 Consolidated assets Total assets Maximum (in billions of yen) Asset-backed commercial paper/loan programs 1,863 — — Asset-backed securitizations 626 66 11 Investments in securitization products 374 136 80 Investment funds 2,249 4,281 614 Trust arrangements and other 22 — — Total 5,134 4,483 705 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, 2017 and September 30, 2017: Assets on balance sheets related to unconsolidated VIEs: March 31, 2017 September 30, 2017 (in billions of yen) Trading account assets 85 100 Investments 254 386 Loans 237 168 Total 576 654 Liabilities on balance sheets and maximum exposure to loss related to unconsolidated VIEs: March 31, 2017 September 30, 2017 (in billions of yen) Payables under securities lending transactions 31 37 Trading account liabilities 1 1 Total 32 38 Maximum exposure to loss (Note) 628 705 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 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 to meet its clients’ needs for off-balance-sheet 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 certain VIEs, where the MHFG Group provides liquidity and credit support facilities, writes credit protection or invests in debt or equity instruments in its role as an arranger, servicer, administrator or asset manager, etc., the Group has the power to determine which assets will be held by the VIEs or to manage and monitor these assets. In addition, through the variable interests above, the Group has the obligation to absorb losses and the right to receive benefits that could potentially be significant to the VIEs. Therefore, the Group consolidates such VIEs. The MHFG Group established certain VIEs to securitize its own mortgage loans. The Group provides servicing for and holds retained subordinated beneficial interests in the securitized mortgage loans. In addition, the Group retains credit exposure in the form of guarantees on these loans. In its role as a servicer, the Group has the power to direct the entity’s activities that most significantly impact the entity’s economic performance by managing defaulted mortgage loans. In addition, through its retained interests and its aforementioned involvement as a guarantor, the Group has the obligation to absorb losses and the right to receive benefits that could potentially be significant to the entity. Therefore, the Group consolidates such VIEs. 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. However, 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 consolidates certain investment funds where it is deemed to be the primary beneficiary. Prior to April 1, 2016, the Group determined that certain investment funds managed by the Group that had attributes of an investment company (or similar entity) qualified for the deferral from certain requirements of ASC 810 that originated from Statement of Financial Accounting Standards (“SFAS”) No.167 “Amendments to FASB Interpretation No.46(R)” (“SFAS No.167”). For these funds, the Group determined whether it was the primary beneficiary by evaluating whether it absorbed the majority of expected losses, received the majority of expected residual returns, or both. On April 1, 2016, the Group adopted ASU No.2015-02, No.2015-02”), The Group adopted ASU No.2015-02 No.2015-02 No.2015-02, 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. 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 16 “Commitments and contingencies” for the balances of guaranteed trust principal that are not consolidated at March 31, 2017 and September 30, 2017. With respect to non-guaranteed non-guaranteed 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. 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. 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” (“ASC 860”) 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, 2016 and 2017, 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, 2017 and September 30, 2017. 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 ¥244 billion and ¥91 billion as of March 31, 2017, and ¥235 billion and ¥113 billion as of September 30, 2017, respectively. Liabilities associated with securitization and loan participation transactions are presented as Payables under securities lending transactions and Other short-term borrowings or Long-term debt, respectively, on the consolidated balance sheets.

Fee and commission income

Fee and commission income	6 Months Ended
	Sep. 30, 2017
Fee and commission income	18. Fee and commission income Details of Fee and commission income for the six months ended September 30, 2016 and 2017 are as follows: Six months ended September 30, 2016 2017 (in millions of yen) Securities-related business 75,145 85,897 Deposits and lending business 85,340 65,081 Remittance business 53,858 54,166 Asset management business 29,548 50,322 Trust fees 23,134 25,966 Fees for other customer services 125,437 119,799 Total 392,462 401,231 Securities-related business fees consist of broker’s fees and markups on securities underwriting and other securities related activities. Remittance business fees consist of service charges for funds transfer and collections. Asset management business fees consist of investment trust management fees and investment advisory fees. Trust fees are earned primarily by fiduciary asset management and administration services for corporate pension plans, investment funds, and other. Fees for other customer services include fees related to the MHFG Group’s agency business, guarantee related business, and other.

Fair value

Fair value	6 Months Ended
	Sep. 30, 2017
Fair value	19. 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 valuation techniques based on whether the inputs to those valuation techniques are observable or unobservable. The standard describes three levels of inputs that may be used to measure fair value: 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 “ Investments” 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, 2017, 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 Ginnie Mae 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 foreign currency denominated securitization products such as RMBS, CMBS, and ABS 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. As it pertains to investment funds, exchange-traded funds (“ETF”) are generally classified in Level 1. 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 Investments The fair values of available-for-sale non-binding Other investments, except for investments held by consolidated investment companies, have not been measured at fair value on a recurring basis. Investments held by consolidated investment companies mainly consist of marketable and non-marketable non-marketable Non-marketable Long-term debt Where fair value accounting has been elected for structured notes, the fair values are determined by incorporating the fair values of embedded derivatives that are primarily derived by using the same procedures described for derivative financial instruments above. Such instruments are classified in Level 2 or Level 3 depending on the observability of significant inputs to the model used in determining the fair value of the embedded derivatives. Items measured at fair value on a recurring basis Assets and liabilities measured at fair value on a recurring basis at March 31, 2017 and September 30, 2017, including those for which the MHFG Group has elected the fair value option, are summarized below: March 31, 2017 Level 1 Level 2 Level 3 Assets/ (in billions of yen) Assets: Trading securities (1) Japanese government bonds 1,485 23 — 1,508 Japanese local government bonds — 69 — 69 U.S. Treasury bonds and federal agency securities 2,883 80 — 2,963 Other foreign government bonds 1,127 457 — 1,584 Agency mortgage-backed securities 1,335 638 — 1,973 Residential mortgage-backed securities — — 15 15 Commercial mortgage-backed securities — 3 — 3 Certificates of deposit and commercial paper — 554 — 554 Corporate bonds and other 3 1,449 1,052 2,504 Equity securities 1,661 20 23 1,704 Trading securities measured at net asset value (2) 678 Derivatives: Interest rate contracts 37 8,442 27 8,506 Foreign exchange contracts 28 2,709 8 2,745 Equity-related contracts 31 89 14 134 Credit-related contracts — 33 2 35 Other contracts 1 11 11 23 Available-for-sale Japanese government bonds 9,543 720 — 10,263 Japanese local government bonds — 284 — 284 U.S. Treasury bonds and federal agency securities 1,144 — — 1,144 Other foreign government bonds 346 589 — 935 Agency mortgage-backed securities 134 709 — 843 Residential mortgage-backed securities — 67 77 144 Commercial mortgage-backed securities — — 224 224 Japanese corporate bonds and other debt securities — 1,834 174 2,008 Foreign corporate bonds and other debt securities — 801 110 911 Equity securities (marketable) 3,717 84 — 3,801 Other investments — — 37 37 Total assets measured at fair value on a recurring basis 23,475 19,665 1,774 45,592 Liabilities: Trading securities sold, not yet purchased 1,993 228 — 2,221 Derivatives: Interest rate contracts 46 8,426 1 8,473 Foreign exchange contracts 20 2,591 — 2,611 Equity-related contracts 129 61 39 229 Credit-related contracts — 34 2 36 Other contracts 1 10 11 22 Long-term debt (3) — 903 593 1,496 Total liabilities measured at fair value on a recurring basis 2,189 12,253 646 15,088 September 30, 2017 Level 1 Level 2 Level 3 Assets/ (in billions of yen) Assets: Trading securities (1) Japanese government bonds 3,012 29 — 3,041 Japanese local government bonds — 48 — 48 U.S. Treasury bonds and federal agency securities 3,832 295 — 4,127 Other foreign government bonds 1,368 449 — 1,817 Agency mortgage-backed securities 1,264 742 — 2,006 Residential mortgage-backed securities — — 14 14 Certificates of deposit and commercial paper — 708 — 708 Corporate bonds and other 9 1,929 1,086 3,024 Equity securities 1,625 — 22 1,647 Trading securities measured at net asset value (2) 681 Derivatives: Interest rate contracts 40 7,600 22 7,662 Foreign exchange contracts 20 2,458 6 2,484 Equity-related contracts 40 93 18 151 Credit-related contracts — 27 2 29 Other contracts 2 7 9 18 Available-for-sale Japanese government bonds 8,926 732 — 9,658 Japanese local government bonds — 254 — 254 U.S. Treasury bonds and federal agency securities 850 — — 850 Other foreign government bonds 364 608 — 972 Agency mortgage-backed securities 161 730 — 891 Residential mortgage-backed securities — 69 68 137 Commercial mortgage-backed securities — — 257 257 Japanese corporate bonds and other debt securities — 1,785 165 1,950 Foreign corporate bonds and other debt securities — 793 97 890 Equity securities (marketable) 4,236 57 — 4,293 Other investments — — 39 39 Total assets measured at fair value on a recurring basis 25,749 19,413 1,805 47,648 Liabilities: Trading securities sold, not yet purchased 2,296 269 4 2,569 Derivatives: Interest rate contracts 39 7,618 1 7,658 Foreign exchange contracts 16 2,382 — 2,398 Equity-related contracts 161 67 44 272 Credit-related contracts — 29 2 31 Other contracts 2 7 8 17 Long-term debt (3) — 1,381 563 1,944 Total liabilities measured at fair value on a recurring basis 2,514 11,753 622 14,889 Notes: (1) Trading securities include foreign currency denominated securities for which the MHFG Group elected the fair value option. (2) 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, 2017 and September 30, 2017 were ¥33 billion and ¥29 billion, respectively. (3) Amounts represent items for which the Group elected the fair value option. 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, 2016 and 2017: Six months ended September 30, 2016 April 1, Gains Gains Transfers Transfers Purchases Sales Issuances Settle- September 30, Change in (losses) (6) (in billions of yen) Assets: Trading securities: Residential mortgage-backed securities 21 — (2) — — — — — — (4 ) 17 — Commercial mortgage-backed securities 2 — (2) — — — — — — (2 ) — — Corporate bonds and 720 (53 ) (2) — 280 (2 ) 343 (241 ) — (71 ) 976 (39 ) Equity securities 21 4 (2) — — — — (7 ) — — 18 4 Derivatives, net (1) Interest rate contracts 26 (4 ) (2) — — — — — — — 22 (3 ) Foreign exchange contracts 7 6 (2) — — — — — — (7 ) 6 — Equity-related contracts 5 (13 ) (2) — — — — — — (2 ) (10 ) (19 ) Credit-related contracts (1 ) 1 (2) — — — — — — — — — Other contracts 1 — (2) — — — — — — — 1 — Available-for-sale Residential mortgage-backed securities 123 — (3) — (4) — — — (1 ) — (22 ) 100 — Commercial mortgage-backed securities 187 — (3) — (4) — — 20 — — (9 ) 198 — Japanese corporate bonds and other debt securities 174 — (3) 22 (4) — — 1 (4 ) — (17 ) 176 — Foreign corporate bonds and other debt securities 108 1 (3) (7 ) (4) — — 10 — — (5 ) 107 — Other investments 42 (3 ) (3) — — — 11 — — (13 ) 37 (1 ) Liabilities: Trading securities sold, not yet purchased — — (2) — 1 — (32 ) 32 — — 1 — Long-term debt 623 9 (5) — — (12 ) — — 147 (158 ) 591 5 Six months ended September 30, 2017 April 1, Gains Gains Transfers Transfers Purchases Sales Issuances Settle- September 30, Change in (losses) (6) (in billions of yen) Assets: Trading securities: Residential mortgage-backed securities 15 — (2) — — — — — — (1 ) 14 — Corporate bonds and 1,052 18 (2) — 123 (240 ) 562 (276 ) — (153 ) 1,086 20 Equity securities 23 (1 ) (2) — — — — — — — 22 (1 ) Derivatives, net (1) Interest rate contracts 26 (6 ) (2) — — — — — — 1 21 (6 ) Foreign exchange contracts 8 (2 ) (2) — — — — — — — 6 (2 ) Equity-related contracts (25 ) (7 ) (2) — — — — — — 6 (26 ) (8 ) Other contracts — — (2) — — — — — — 1 1 — Available-for-sale Residential mortgage-backed securities 77 — (3) — (4) — — 1 — — (10 ) 68 — Commercial mortgage-backed securities 224 — (3) — (4) — — 40 (7 ) — — 257 — Japanese corporate bonds and other debt securities 174 (1 ) (3) (3 ) (4) — — 11 — — (16 ) 165 (1 ) Foreign corporate bonds and other debt securities 110 — (3) 1 (4) 15 (29 ) — — — — 97 — Other investments 37 — (3) — — — 12 — — (10 ) 39 — Liabilities: Trading securities sold, not yet purchased — — (2) — — — (57 ) 61 — — 4 — Long-term debt 593 (13 ) (5) — 1 (10 ) — — 47 (81 ) 563 (14 ) 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, Foreign exchange gains (losses)—net or Other noninterest income (expenses). (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 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, 2016 and 2017. Transfers between levels Transfers of assets or liabilities between levels of the fair value hierarchy are assumed to occur at the beginning of the period. During the six months ended September 30, 2016, the transfers into Level 3 included ¥280 billion of Trading securities and ¥1 billion of Trading securities sold, not yet purchased. Transfers into Level 3 for Trading securities and Trading securities sold, not yet purchased were primarily due to decreased liquidity for certain Japanese and foreign corporate bonds. During the six months ended September 30, 2016, the transfers out of Level 3 included ¥2 billion of Trading securities and ¥12 billion of Long-term debt. Transfers out of Level 3 for Trading securities were primarily due to increased price transparency for certain Japanese and foreign corporate bonds. Transfers out of Level 3 for Long-term debt were primarily due to changes in the impact of unobservable inputs on the value of certain structured notes. During the six months ended September 30, 2017, the transfers into Level 3 included ¥123 billion of Trading securities, ¥15 billion of Available-for-sale Available-for-sale Available-for-sale Available-for-sale 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, 2017 and September 30, 2017: March 31, 2017 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 92 Discounted cash flow Price-based Prepayment rate Recovery rate Discount margin 0% -18% 0% - 1% 15bps - 170bps 7% Commercial 224 Discounted cash flow Discount margin 4bps - 205bps 28bps Corporate bonds and 1,336 Discounted cash flow Prepayment rate (1) (1) (1) (1) (2) 16% - 30% 1% - 2% 60% - 68% 8bps - 1,181bps 29% Derivatives, net: Interest rate 26 Internal valuation model (3) IR – IR correlation (4) 23% - 100% Foreign exchange 8 Internal valuation model (3) FX – IR correlation FX – FX correlation (4) 5% - 52% 55% - 55% 0% - 63% Equity-related (25 ) Internal valuation model (3) Equity – IR correlation 25% - 25% 6% - 59% Credit-related — Internal valuation model (3) Default rate Credit correlation 0% - 5% 30% - 100% Long-term debt 593 Internal valuation model (3) IR – IR correlation Credit correlation 23% - 100% 55% - 55% 0% - 3% 33% - 100% September 30, 2017 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 82 Discounted cash flow Prepayment rate Recovery rate 3% - 17% 0% - 1% 100% - 100% 7% Commercial 257 Discounted cash flow Discount margin 2bps - 93bps 27bps Corporate bonds and other debt 1,348 Discounted cash flow Prepayment rate (1) (1) (1) (1) (2) 22% - 39% 1% - 2% 60% - 68% 16bps - 1,179bps 39% Derivatives, net: Interest rate 21 Internal valuation model (3) IR – IR correlation (4) 23% - 100% Foreign exchange contracts 6 Internal valuation model (3) FX – IR correlation (4) 5% - 54% 59% - 59% 0% - 63% Equity-related (26 ) Internal valuation model (3) Equity – IR correlation Equity volatility 25% - 25% Credit-related — Internal valuation model (3) Default rate Credit correlation 0% - 3% 26% - 100% Long-term debt 563 Internal valuation model (3) IR – IR correlation FX – IR correlation Credit correlation 23% - 100% 59% - 59% 0% - 2% 32% - 100% 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) Weighted averages are calculated by weighting each input by the relative fair value of the respective financial instruments. IR = Interest rate FX = Foreign exchange Sensitivities to unobservable inputs and interrelationships between unobservable inputs The following is a description of the sensitivities and 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 of the interest rate over a benchmark market interest rate such as LIBOR or swap rates. It primarily consists of a risk premium component which is the amount of compensation that market participants require due to the uncertainty inherent in the financial instruments’ cash flows resulting from credit risk. An increase in discount margin would generally impact the valuation of the fair values of financial instruments negatively. (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, 2017 and September 30, 2017: March 31, 2017 Total Level 1 Level 2 Level 3 Aggregate cost (in billions of yen) Assets: Loans 124 — — 124 194 Loans held-for-sale 7 — 7 — 8 Other investments 7 6 — 1 11 Premises and equipment—net 7 — 6 1 11 Total assets measured at fair value on a nonrecurring basis 145 6 13 126 224 September 30, 2017 Total Level 1 Level 2 Level 3 Aggregate cost (in billions of yen) Assets: Loans 120 — — 120 183 Loans held-for-sale 5 — 5 — 8 Other investments — — — — 1 Total assets measured at fair value on a nonrecurring basis 125 — 5 120 192 Loans in the table above have been impaired and measured based upon the fair value of the underlying collateral. Loans held-for-sale Other investments in the table above, which consist of certain equity method investments and non-marketable non-marketable non-marketable non-marketable Premises and equipment—net in the table above have been impaired and written down to fair value. Fair value option The MHFG Group elected the fair value option for certain eligible financial instruments described below. Foreign currency denominated available-for-sale The MHFG Group elected the fair value option for foreign currency denominated available-for-sale available-for-sale Certain hybrid financial instruments The MHFG Group issues structured notes as part of its client-driven activities. Structured notes are debt instruments that contain embedded derivatives. The Group elected the fair value option for certain structured notes to mitigate accounting mismatches and to achieve operational simplifications. In addition, the Group measures certain notes that contain embedded derivatives at fair value under the practicability exception. These notes continue to be reported in Long-term debt and interest on these notes continues to be reported in Interest expense on long-term debt based on the contractual rates. The differences between the aggregate fair value of these notes and the aggregate unpaid principal balance of such instruments were ¥36 billion and ¥8 billion at March 31, 2017 and September 30, 2017, respectively. The net unrealized gains (losses) resulting from changes in fair values of these notes of ¥2 billion and ¥(28) billion, which included the fair value changes attributable to changes in the Group’s own credit risk, were recorded in Other noninterest income (expenses) for the six months ended September 30, 2016 and 2017, respectively. 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 assumptions, discounted cash flow models or other valuation techniques. Such estimation methods are described in more detail below. These estimates could be significantly affected by different sets of assumptions. There are certain limitations to management’s best judgment in estimating fair values of financial instruments and inherent subjectivity involved in estimation methodologies and assumptions used to estimate fair value. Accordingly, the net realizable or liquidation values could be materially different from the estimates presented below. ASC 825 does not require the disclosure of the fair value of nonfinancial instruments. 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, 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 Loans Performing loans have been fair valued as groups of similar loans based on the type of loan, credit quality, prepayment assumptions and remaining maturity. The fair value of performing 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 impaired loans is determined based on either discounted cash flows incorporating the Group’s best estimate of the expected future cash flows or the fair value of the underlying collateral, if impaired loans are collateral dependent. 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 7 “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 trust accounts The carrying value of due to trust accounts approximates the fair value since they generally have short-term maturities with interest rates that approximate market rates. Other short-term borrowings The carrying value of the majority of other short-term borrowings approximates the fair value since they generally have short-term maturities with interest rates that approximate market rates. The fair value of certain borrowings is estimated based on discounted cash flow analysis using interest rates approximating the MHFG Group’s incremental borrowing rates for instruments with similar maturities. Long-term debt Long-term debt is fair valued using quoted market prices, if available. Otherwise, the fair value of long-term debt is estimated based on discounted cash flow analysis using interest rates approximating the MHFG Group’s incremental borrowing rates for instruments with similar maturities. Other financial liabilities The carrying value of other financial liabilities, which primarily consist of accounts payable to brokers, dealers, and customers for securities transactions, accrued expenses and collateral accepted for derivative transactions, approximates the fair value since they generally have short-term maturities with interest rates that approximate market rates. The majority of other financial liabilities is classified as Level 2, and included in the table in Note 7 “Other assets and liabilities”. The fair value of certain off-balance-sheet The following table shows the carrying amounts and fair values at March 31, 2017 and September 30, 2017, of certain financial instruments, excluding financial instruments which are carried at fair value on a recurring basis and those outside the scope of ASC 825 such as equity method investments as defined in ASC 323, “Investments—Equity Method and Joint Ventures” (“ASC 323”) and lease contracts as defined in ASC 840, “Leases” (“ASC 840”): March 31, 2017 Carrying Estimated fair value Total Level 1 Level 2 Level 3 (in billions of yen) Financial assets: Cash and due from banks, call loans and funds sold, and receivables under resale agreements and securities borrowing transactions 60,943 60,943 1,063 59,880 — Investments 3,817 3,846 3,846 — — Loans, net of allowance for loan losses (Note) 81,662 82,696 — — 82,696 Financial liabilities: Noninterest-bearing deposits, call money and funds purchased, and payables under repurchase agreements and securities lending transactions 42,205 42,205 20,544 21,661 — Interest-bearing deposits 110,125 110,124 56,738 53,386 — Due to trust accounts 4,123 4,123 — 4,123 — Other short-term borrowings 1,477 1,477 — 1,477 — Long-term debt 13,009 13,078 — 12,120 958 September 30, 2017 Carrying Estimated fair value Total Level 1 Level 2 Level 3 (in billions of yen) Financial assets: Cash and due from banks, call loans and funds sold, and receivables under resale agreements and securities borrowing transactions 65,291 65,291 909 64,382 — Investments 3,127 3,148 3,148 — — Loans, net of allowance for loan losses (Note) 83,401 84,306 — — 84,306 Financial liabilities: Noninterest-bearing deposits, call money

Offsetting of financial assets

Offsetting of financial assets and financial liabilities	6 Months Ended
	Sep. 30, 2017
Offsetting of financial assets and financial liabilities	20. 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 provides information about the offsetting of financial assets and financial liabilities at March 31, 2017 and September 30, 2017. The table includes derivatives, repurchase and resale agreements, and securities lending and borrowing transactions that are subject to enforceable master netting arrangements or similar agreements irrespective of whether or not they are offset on the Group’s consolidated balance sheets. Amounts not offset on ( 3 ) Gross amounts Gross amounts offset on the Net amounts presented on the (2) Financial instruments ( 4 ) Cash collateral Net (in billions of yen) March 31, 2017 Assets (1) Derivatives 10,608 — 10,608 (8,966 ) (620 ) 1,022 Receivables under resale agreements 8,698 — 8,698 (8,662 ) — 36 Receivables under securities borrowing transactions 3,127 — 3,127 (3,116 ) — 11 Total 22,433 — 22,433 (20,744 ) (620 ) 1,069 Liabilities (1) Derivatives 10,405 — 10,405 (8,866 ) (901 ) 638 Payables under repurchase agreements 17,446 — 17,446 (17,391 ) — 55 Payables under securities lending transactions 1,458 — 1,458 (1,455 ) — 3 Total 29,309 — 29,309 (27,712 ) (901 ) 696 September 30, 2017 Assets (1) Derivatives 9,806 — 9,806 (8,370 ) (504 ) 932 Receivables under resale agreements 9,162 — 9,162 (9,105 ) — 57 Receivables under securities borrowing transactions 3,192 — 3,192 (3,172 ) — 20 Total 22,160 — 22,160 (20,647 ) (504 ) 1,009 Liabilities (1) Derivatives 9,658 — 9,658 (8,120 ) (972 ) 566 Payables under repurchase agreements 18,453 — 18,453 (18,275 ) — 178 Payables under securities lending transactions 2,315 — 2,315 (2,277 ) — 38 Total 30,426 — 30,426 (28,672 ) (972 ) 782 Notes: (1) Amounts relating to master netting arrangements or similar agreements where the MHFG Group does not have the legal right of set-off over-the-counter OTC-cleared (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.

Repurchase agreements and secur

Repurchase agreements and securities lending transactions accounted for as secured borrowings	6 Months Ended
	Sep. 30, 2017
Repurchase agreements and securities lending transactions accounted for as secured borrowings	21. 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, 2017 and September 30, 2017: Overnight and Up to 30 days 31-90 days Greater than 90 days Total (in billions of yen) March 31, 2017 Repurchase agreements 249 12,700 3,897 1,124 17,970 Securities lending transactions 320 1,359 — 240 1,919 Total 569 14,059 3,897 1,364 19,889 September 30, 2017 Repurchase agreements 534 13,199 4,596 1,193 19,522 Securities lending transactions 2,177 463 — 233 2,873 Total 2,711 13,662 4,596 1,426 22,395 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, 2017 and September 30, 2017: Repurchase Securities lending (in billions of yen) March 31, 2017 Japanese government bonds and Japanese local government bonds 1,127 1,152 Foreign government bonds and foreign agency mortgage-backed securities 15,782 375 Commercial paper and corporate bonds 294 47 Equity securities 578 320 Other 189 25 Total (Note) 17,970 1,919 September 30, 2017 Japanese government bonds and Japanese local government bonds 1,156 1,767 Foreign government bonds and foreign agency mortgage-backed securities 17,332 453 Commercial paper and corporate bonds 377 47 Equity securities 514 583 Other 143 23 Total (Note) 19,522 2,873 Note: Amounts exceeded the gross amounts recognized in Note 20 “Offsetting of financial assets and financial liabilities” by ¥985 billion and ¥1,627 billion, at March 31, 2017 and September 30, 2017, 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 daily basis, diversifying the maturities and counterparties, and using mainly highly liquid securities.

Business segment information

Business segment information	6 Months Ended
	Sep. 30, 2017
Business segment information	22. Business segment information The MHFG Group consists of the following five in-house companies which are categorized based on a customer segment: the Retail & Business Banking Company, the Corporate & Institutional Company, the Global Corporate Company, the Global Markets Company, and the Asset Management Company. These customer segments are regarded as operating segments and constitute reportable segments. 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 risk, such as interest rate risk, equity risk, and credit risk. 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 each business segment’s net business profits with income before income tax expense under U.S. GAAP. Management does not use information on business segment’s assets to allocate resources and assess performance and has not prepared information on the segment’s assets. Accordingly, information on the segment’s assets is not available. MHFG (Consolidated) Six months ended September 30, 2016 Retail & Corporate & Global Global Asset Others (2)(3) Total (in billions of yen) Gross profits 348.0 215.2 183.4 333.6 24.4 (14.9 ) 1,089.7 General and administrative expenses 359.8 96.5 117.9 90.1 15.0 1.2 680.5 Equity in earnings (losses) of equity method investees—net 8.8 0.6 1.0 — (0.1 ) 1.0 11.3 Others — — — — — (17.3 ) (17.3 ) Net business profits (losses) (1) (3.0 ) 119.3 66.5 243.5 9.3 (32.4 ) 403.2 MHFG (Consolidated) Six months ended September 30, 2017 Retail & Corporate & Global Global Asset Others (2) Total (in billions of yen) Gross profits 343.0 192.0 160.2 236.2 24.9 3.5 959.8 General and administrative expenses 358.6 97.3 122.5 99.7 13.9 26.3 718.3 Equity in earnings (losses) of equity method investees—net 7.5 0.6 1.4 — 0.3 0.8 10.6 Others — — — — — (10.5 ) (10.5 ) Net business profits (losses) (1) (8.1 ) 95.3 39.1 136.5 11.3 (32.5 ) 241.6 Notes: (1) Net business profits is used in Japan as a measure of the profitability of core banking operations, and is defined as gross profits (or the sum of net interest income, fiduciary income, net fee and commission income, net trading income and net other operating income) less general and administrative expenses. Measurement of net business profits is required for regulatory reporting to the Financial Services Agency. (2) “Others” includes items which should be eliminated as internal transactions between each segment on a consolidated basis. (3) Beginning on April 1, 2017, new allocation methods for transactions between each segment and “Others” have been applied. Figures for the six months ended September 30, 2016 have been restated for the new allocation methods and “Equity in earnings (losses) of equity method investees—net” has been presented as a new item in connection with the use of the new allocation methods. 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, to the corresponding items in the accompanying consolidated statements of income. A reconciliation of total net business profits under the internal management reporting systems for the six months ended September 30, 2016 and 2017 presented above to income before income tax expense shown on the consolidated statements of income is as follows: Six months ended September 30, 2016 2017 (in billions of yen) Net business profits 403.2 241.6 U.S. GAAP adjustments 14.8 95.7 (Provision) credit for loan losses (0.6 ) 118.0 Net gains (losses) related to equity investments 64.5 100.9 Non-recurring (4.7 ) (3.6 ) Gains on disposal of premises and equipment 3.5 4.6 (Provision) credit for losses on off-balance-sheet 7.9 4.2 Others—net (31.3 ) (48.5 ) Income before income tax expense 457.3 512.9

Basis of presentation (Policies

Basis of presentation (Policies)	6 Months Ended
	Sep. 30, 2017
Basis of presentation	Basis of presentation Mizuho Financial Group, Inc. (“MHFG”) is a joint stock corporation with limited liability under the laws of Japan. 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 22 “Business segment information”. The accompanying consolidated financial statements have been prepared in accordance with 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 and certain subsidiaries’ interim financial reporting period ends on June 30. The necessary adjustments have been made to the consolidated financial statements if significant transactions took place during the three-month period. When determining whether to consolidate investee entities, the MHFG Group performed a careful 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 the 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. The amounts of asset management business fee income and expenses for the six months ended September 30, 2016 have been reclassified from Other noninterest income and Other noninterest expenses to Fee and commission income and Fee and commission expenses, respectively, in order to conform to the current year’s presentation. Such reclassifications had no effect on net income or shareholder’s equity. 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, 2017. 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 loan losses, allowance for losses on off-balance-sheet

Business combination (Tables)

Business combination (Tables)	6 Months Ended
	Sep. 30, 2017
Summary of Consideration Paid for DIAM, Amounts of Acquired Assets and Assumed Liabilities Recognized and Fair Value of Noncontrolling Interest at Acquisition Date in DIAM	The following table summarizes the consideration paid for DIAM and the amounts of the acquired assets and assumed liabilities recognized at the acquisition date, as well as the fair value at the acquisition date of the noncontrolling interest in DIAM. There were no material acquisition-related costs that were recognized separately from the acquisition of the assets and the assumption of the liabilities. At October 1, (in millions of yen) Consideration: Equity instruments (1,038,408 common shares of MHAM) 28,842 Fair value of total consideration transferred 28,842 Fair value of equity interests in DIAM held by MHFG before the business combination 72,106 100,948 Recognized amounts of identifiable assets acquired: Cash and due from banks 831 Interest-bearing deposits in other banks 12,873 Trading account assets 266 Investments 12,234 Premises and equipment-net 3,546 Accrued income 7,882 Intangible assets (Note) 53,037 Deferred tax assets 1,003 Other assets 2,208 Recognized amounts of identifiable liabilities assumed: Trading account liabilities 304 Income taxes payable 918 Deferred taxes liabilities 16,238 Accrued expenses 5,392 Other liabilities 3,041 Total identifiable net assets 67,987 Goodwill 76,225 Noncontrolling interest in DIAM 43,264 100,948 Note: Amount represents customer relationships subject to amortization, of which the weighted-average amortization period is 16.9 years.

Investments (Tables)

Investments (Tables)	6 Months Ended
	Sep. 30, 2017
Amortized Cost, Gross Unrealized Gains and Losses, and Fair Value of Available-for-Sale and Held-to-Maturity Securities	The amortized cost, gross unrealized gains and losses, and fair value of available-for-sale held-to-maturity Amortized cost Gross unrealized Gross unrealized Fair value (in millions of yen) March 31, 2017 Available-for-sale Debt securities: Japanese government bonds 10,256,512 22,782 16,408 10,262,886 Japanese local government bonds 279,864 4,841 233 284,472 U.S. Treasury bonds and federal agency securities 1,148,389 10 4,578 1,143,821 Other foreign government bonds 933,942 1,246 236 934,952 Agency mortgage-backed securities (1) 832,738 15,500 5,441 842,797 Residential mortgage-backed securities 142,879 1,838 558 144,159 Commercial mortgage-backed securities 223,105 1,092 282 223,915 Japanese corporate bonds and other debt securities (2) 1,958,472 52,046 2,286 2,008,232 Foreign corporate bonds and other debt securities (3) 909,052 3,377 1,643 910,786 Equity securities (marketable) 1,528,808 2,273,883 1,593 3,801,098 Total 18,213,761 2,376,615 33,258 20,557,118 Held-to-maturity Debt securities: Japanese government bonds 3,059,976 37,168 — 3,097,144 Agency mortgage-backed securities (4) 757,384 121 7,931 749,574 Total 3,817,360 37,289 7,931 3,846,718 September 30, 2017 Available-for-sale Debt securities: Japanese government bonds 9,672,831 5,728 20,335 9,658,224 Japanese local government bonds 251,023 3,007 464 253,566 U.S. Treasury bonds and federal agency securities 853,697 153 4,096 849,754 Other foreign government bonds 971,933 1,708 820 972,821 Agency mortgage-backed securities (1) 880,882 13,981 4,313 890,550 Residential mortgage-backed securities 135,814 1,495 512 136,797 Commercial mortgage-backed securities 256,777 1,063 454 257,386 Japanese corporate bonds and other debt securities (2) 1,903,923 47,293 1,550 1,949,666 Foreign corporate bonds and other debt securities (3) 889,383 2,437 1,552 890,268 Equity securities (marketable) 1,675,207 2,619,270 1,463 4,293,014 Total 17,491,470 2,696,135 35,559 20,152,046 Held-to-maturity Debt securities: Japanese government bonds 2,459,938 28,111 — 2,488,049 Agency mortgage-backed securities (4) 667,548 51 7,852 659,747 Total 3,127,486 28,162 7,852 3,147,796 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 ¥708,557 million and ¥134,240 million, respectively, at March 31, 2017, and ¥729,895 million and ¥160,655 million, respectively, at September 30, 2017. 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. (2) Other debt securities presented in this line primarily consist of certificates of deposit (“CDs”), of which the total fair values were ¥155,138 million at March 31, 2017, and ¥146,136 million at September 30, 2017. (3) Other debt securities presented in this line primarily consist of CDs and asset-backed securities (“ABS”), of which the total fair values were ¥258,059 million at March 31, 2017, and ¥290,380 million at September 30, 2017. (4) All Agency mortgage-backed securities presented in this line are Ginnie Mae securities.
Amortized Cost and Fair Value of Available-for-Sale and Held-to-Maturity Debt Securities by Contractual Maturity	Securities not due at a single maturity date and securities embedded with call or prepayment options, such as mortgage-backed securities, are included in the table below based on their contractual maturities. 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 4,076,063 4,201,851 1,394,917 — 9,672,831 Japanese local government bonds 30,530 115,552 100,844 4,097 251,023 U.S. Treasury bonds and federal agency securities 716,047 — 137,650 — 853,697 Other foreign government bonds 706,741 255,529 9,663 — 971,933 Agency mortgage-backed securities — — — 880,882 880,882 Residential mortgage-backed securities — — — 135,814 135,814 Commercial mortgage-backed securities 7,500 159,599 80,278 9,400 256,777 Japanese corporate bonds and other debt securities 395,022 963,809 351,649 193,443 1,903,923 Foreign corporate bonds and other debt securities 468,526 350,022 67,910 2,925 889,383 Total 6,400,429 6,046,362 2,142,911 1,226,561 15,816,263 Held-to-maturity Debt securities: Japanese government bonds 860,031 1,120,025 479,882 — 2,459,938 Agency mortgage-backed securities — — — 667,548 667,548 Total 860,031 1,120,025 479,882 667,548 3,127,486 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 4,073,609 4,200,457 1,384,158 — 9,658,224 Japanese local government bonds 30,587 116,166 102,671 4,142 253,566 U.S. Treasury bonds and federal agency securities 715,889 — 133,865 — 849,754 Other foreign government bonds 706,840 256,228 9,753 — 972,821 Agency mortgage-backed securities — — — 890,550 890,550 Residential mortgage-backed securities — — — 136,797 136,797 Commercial mortgage-backed securities 7,504 159,771 80,935 9,176 257,386 Japanese corporate bonds and other debt securities 395,270 965,654 353,485 235,257 1,949,666 Foreign corporate bonds and other debt securities 468,546 350,541 68,269 2,912 890,268 Total 6,398,245 6,048,817 2,133,136 1,278,834 15,859,032 Held-to-maturity Debt securities: Japanese government bonds 861,783 1,125,592 500,674 — 2,488,049 Agency mortgage-backed securities — — — 659,747 659,747 Total 861,783 1,125,592 500,674 659,747 3,147,796
Other-Than-Temporary Impairment Losses on Available-for-Sale Securities	The following table shows the other-than-temporary impairment losses on available-for-sale held-to-maturity Six months ended September 30, 2016 2017 (in millions of yen) Available-for-sale Debt securities 56 1,000 Equity securities 10,016 2,521 Total 10,072 3,521
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 Gross Fair Gross Fair value Gross (in millions of yen) March 31, 2017 Available-for-sale Debt securities: Japanese government bonds 5,574,649 15,796 95,612 612 5,670,261 16,408 Japanese local government bonds 58,700 233 — — 58,700 233 U.S. Treasury bonds and federal agency securities 1,013,962 4,578 — — 1,013,962 4,578 Other foreign government bonds 334,300 230 8,327 6 342,627 236 Agency mortgage-backed securities (1) 195,887 3,705 42,501 1,736 238,388 5,441 Residential mortgage-backed securities 5,873 3 28,994 555 34,867 558 Commercial mortgage-backed securities 8,314 218 17,634 64 25,948 282 Japanese corporate bonds and other debt securities 470,602 2,062 158,713 224 629,315 2,286 Foreign corporate bonds and other debt securities 202,347 1,353 77,699 290 280,046 1,643 Equity securities (marketable) 30,688 383 4,117 1,210 34,805 1,593 Total 7,895,322 28,561 433,597 4,697 8,328,919 33,258 Held-to-maturity Debt securities: Agency mortgage-backed securities (2) 460,882 3,518 259,466 4,413 720,348 7,931 Total 460,882 3,518 259,466 4,413 720,348 7,931 September 30, 2017 Available-for-sale Debt securities: Japanese government bonds 7,198,653 9,958 1,420,926 10,377 8,619,579 20,335 Japanese local government bonds 89,207 374 7,802 90 97,009 464 U.S. Treasury bonds and federal agency securities 470,397 785 79,294 3,311 549,691 4,096 Other foreign government bonds 551,664 785 72,166 35 623,830 820 Agency mortgage-backed securities (1) 227,245 2,239 77,620 2,074 304,865 4,313 Residential mortgage-backed securities 18,093 43 25,344 469 43,437 512 Commercial mortgage-backed securities 41,379 417 12,292 37 53,671 454 Japanese corporate bonds and other debt securities 572,056 1,174 206,284 376 778,340 1,550 Foreign corporate bonds and other debt securities 228,662 1,233 31,828 319 260,490 1,552 Equity securities (marketable) 14,441 1,031 21,709 432 36,150 1,463 Total 9,411,797 18,039 1,955,265 17,520 11,367,062 35,559 Held-to-maturity Debt securities: Agency mortgage-backed securities (2) 406,351 3,725 224,851 4,127 631,202 7,852 Total 406,351 3,725 224,851 4,127 631,202 7,852 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 ¥104,270 million and ¥134,118 million, respectively, at March 31, 2017, and ¥144,319 million and ¥160,546 million, respectively, at September 30, 2017. 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. (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 available-for-sale Six months ended September 30, 2016 2017 (in millions of yen) Gross realized gains 144,796 127,360 Gross realized losses (9,615 ) (10,020 ) Net realized gains (losses) on sales of available-for-sale 135,181 117,340
Summary of Composition of Other Investments	The following table summarizes the composition of Other investments at March 31, 2017 and September 30, 2017: March 31, 2017 September 30, 2017 (in millions of yen) Equity method investments 249,679 255,370 Investments held by consolidated investment companies 37,462 38,779 Other equity interests 307,928 242,923 Total 595,069 537,072

Loans (Tables)

Loans (Tables)	6 Months Ended
	Sep. 30, 2017
Loans Outstanding by Domicile and Industry of Borrower	The table below presents loans outstanding by domicile and industry of borrower at March 31, 2017 and September 30, 2017: March 31, 2017 September 30, 2017 (in millions of yen) Domestic: Manufacturing 8,740,281 8,526,643 Construction and real estate 7,654,016 7,709,245 Services 4,759,225 4,923,838 Wholesale and retail 5,142,003 5,123,176 Transportation and communications 3,490,415 3,413,710 Banks and other financial institutions 4,006,401 4,247,285 Government and public institutions 8,532,246 9,981,557 Other industries (Note) 4,427,349 4,502,531 Individuals: Mortgage loans 9,964,633 9,702,129 Other 939,971 958,159 Total domestic 57,656,540 59,088,273 Foreign: Commercial and industrial 16,872,448 16,915,590 Banks and other financial institutions 6,759,921 6,897,692 Government and public institutions 959,948 1,088,753 Other (Note) 190,724 37,938 Total foreign 24,783,041 24,939,973 Total 82,439,581 84,028,246 Less: Unearned income and deferred loan fees—net 155,675 144,787 Total loans before allowance for loan losses 82,283,906 83,883,459 Note: Other industries of Domestic and Other of Foreign include 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, 2017 and September 30, 2017: Normal obligors Watch obligors (1) A-B C-D Retail (2) Other (3) E1-E2 Retail (2) Other (3) Impaired Total (in millions of yen) March 31, 2017 Domestic: Manufacturing 5,313,232 2,599,760 90,825 67,734 276,771 11,589 1,314 379,056 8,740,281 Construction and real estate 4,199,022 2,641,436 558,321 15,585 165,836 16,023 317 57,476 7,654,016 Services 2,699,487 1,687,515 185,577 910 95,973 23,189 204 66,370 4,759,225 Wholesale and retail 2,244,214 2,369,842 200,003 22,785 124,846 32,911 501 146,901 5,142,003 Transportation and communications 2,584,367 739,781 82,543 1,092 50,319 9,698 — 22,615 3,490,415 Banks and other financial institutions 3,050,605 887,527 1,894 37,907 21,574 353 — 6,541 4,006,401 Government and public institutions 4,059,349 1,600 — 4,471,297 — — — — 8,532,246 Other industries (4) 1,873,137 591,109 3,535 1,906,756 4,613 410 41,179 6,610 4,427,349 Individuals — 289,809 10,312,739 80,566 26,288 89,066 1,434 104,702 10,904,604 Total domestic 26,023,413 11,808,379 11,435,437 6,604,632 766,220 183,239 44,949 790,271 57,656,540 Foreign: Commercial and industrial 9,310,432 4,814,906 173 2,153,757 312,275 — 90,722 190,183 16,872,448 Banks and other financial institutions 5,628,387 592,380 — 480,806 58,348 — — — 6,759,921 Government and public institutions 741,478 214,558 — 1,082 2,801 — — 29 959,948 Other (4) — 6,535 9,439 173,464 124 8 753 401 190,724 Total foreign 15,680,297 5,628,379 9,612 2,809,109 373,548 8 91,475 190,613 24,783,041 Total 41,703,710 17,436,758 11,445,049 9,413,741 1,139,768 183,247 136,424 980,884 82,439,581 September 30, 2017 Domestic: Manufacturing 5,302,937 2,718,865 85,978 46,881 225,293 10,880 239 135,570 8,526,643 Construction and real estate 4,341,519 2,583,327 533,436 8,471 174,429 16,592 — 51,471 7,709,245 Services 2,802,307 1,647,922 181,122 125,114 89,500 21,722 — 56,151 4,923,838 Wholesale and retail 2,241,712 2,395,149 190,225 13,830 110,009 31,369 669 140,213 5,123,176 Transportation and communications 2,511,302 753,838 79,972 1,948 30,502 9,275 — 26,873 3,413,710 Banks and other financial institutions 3,462,891 592,365 1,774 160,314 22,659 220 — 7,062 4,247,285 Government and public institutions 3,237,595 1,600 — 6,742,362 — — — — 9,981,557 Other industries (4) 2,376,483 188,887 3,634 1,918,680 2,368 289 8,927 3,263 4,502,531 Individuals — 300,201 10,081,604 69,829 25,766 84,265 1,275 97,348 10,660,288 Total domestic 26,276,746 11,182,154 11,157,745 9,087,429 680,526 174,612 11,110 517,951 59,088,273 Foreign: Commercial and industrial 9,442,125 4,635,302 206 2,221,178 383,128 — 79,905 153,746 16,915,590 Banks and other financial institutions 5,867,251 563,445 — 411,234 54,835 — 927 — 6,897,692 Government and public institutions 865,441 220,632 — 861 1,800 — — 19 1,088,753 Other (4) — 4,800 9,044 21,800 246 7 1,284 757 37,938 Total foreign 16,174,817 5,424,179 9,250 2,655,073 440,009 7 82,116 154,522 24,939,973 Total 42,451,563 16,606,333 11,166,995 11,742,502 1,120,535 174,619 93,226 672,473 84,028,246 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 impaired. (2) Amounts represent small balance, homogeneous loans which are subject to pool allocations. (3) Non-impaired (4) Other industries of Domestic and Other of Foreign include trade receivables and lease receivables of consolidated VIEs.
Impaired Loans Information	The table below presents impaired loans information at March 31, 2017 and September 30, 2017: Recorded investment (1) Requiring Not (2) Total Unpaid Related (3) Average Interest ( 4 ) (in millions of yen) March 31, 2017 Domestic: Manufacturing 372,241 6,815 379,056 383,812 148,777 375,895 2,859 Construction and real estate 46,130 11,346 57,476 66,006 6,367 66,796 877 Services 58,366 8,004 66,370 72,261 20,122 66,050 1,173 Wholesale and retail 133,466 13,435 146,901 155,023 52,341 148,865 2,261 Transportation and communications 19,386 3,229 22,615 23,568 5,968 24,035 371 Banks and other financial 2,601 3,940 6,541 6,873 962 5,305 50 Other industries 6,484 126 6,610 6,740 1,999 6,053 91 Individuals 51,893 52,809 104,702 114,880 4,935 114,104 1,696 Total domestic 690,567 99,704 790,271 829,163 241,471 807,103 9,378 Foreign: Total foreign 160,563 30,050 190,613 209,129 61,102 169,192 2,040 Total 851,130 129,754 980,884 1,038,292 302,573 976,295 11,418 Recorded investment (1) Requiring Not (2) Total Unpaid Related (3) Average Interest ( 4 ) (in millions of yen) September 30, 2017 Domestic: Manufacturing 130,184 5,386 135,570 140,010 48,786 257,313 914 Construction and real estate 41,808 9,663 51,471 59,519 5,397 54,473 338 Services 46,498 9,653 56,151 63,777 12,280 61,260 432 Wholesale and retail 129,030 11,183 140,213 148,775 49,871 143,557 1,031 Transportation and communications 24,139 2,734 26,873 27,865 7,134 24,744 160 Banks and other financial institutions 3,100 3,962 7,062 7,395 1,433 6,802 29 Other industries 2,184 1,079 3,263 3,393 1,534 4,937 17 Individuals 46,492 50,856 97,348 102,916 4,657 101,025 729 Total domestic 423,435 94,516 517,951 553,650 131,092 654,111 3,650 Foreign: Total foreign 127,433 27,089 154,522 172,523 48,620 172,567 1,069 Total 550,868 121,605 672,473 726,173 179,712 826,678 4,719 Notes: (1) Amounts represent the outstanding balances of nonaccrual loans. The MHFG Group’s policy for placing loans in nonaccrual status corresponds to the Group’s definition of impaired loans. (2) These impaired loans do not require an allowance for loan losses because the MHFG Group has sufficient collateral to cover probable loan losses. (3) The allowance for loan losses on impaired loans includes the allowance for groups of small balance, homogeneous loans which were collectively evaluated for impairment, in addition to the allowance for those loans that were individually evaluated for impairment. The total carrying amount of the groups of small balance, homogeneous loans at March 31, 2017 and September 30, 2017 was ¥302,251 million and ¥266,915 million, respectively. (4) Amounts represent gross interest income on impaired loans which were included in Interest income on loans in the consolidated statements of income.
Troubled Debt Restructurings Entered into During Periods by Type of Concession Granted	The following table presents TDRs that were entered into during the six months ended September 30, 2016 and 2017: Loan forgiveness or debt to equity swaps Interest rate reduction Recorded investment (Note) Charge-offs (in millions of yen) September 30, 2016 Domestic: Manufacturing — — 54,476 Construction and real estate — — 8,596 Services — — 21,951 Wholesale and retail — — 87,237 Transportation and communications — — 8,656 Banks and other financial institutions — — 3,198 Other industries — — 2,274 Individuals — — 9,205 Total domestic — — 195,593 Foreign: Total foreign — — 10,849 Total — — 206,442 September 30, 2017 Domestic: Manufacturing — — 55,611 Construction and real estate — — 9,045 Services — — 18,740 Wholesale and retail — — 74,625 Transportation and communications — — 12,244 Banks and other financial institutions — — 3,461 Individuals — — 7,619 Total domestic — — 181,345 Foreign: Total foreign — — 13,303 Total — — 194,648 Note: Amounts represent the book values of loans immediately after the restructurings.
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, 2016 and 2017 with respect to the loans modified as TDRs within the previous twelve months: Recorded investment September 30, 2016 September 30, 2017 (in millions of yen) Domestic: Manufacturing 1,801 2,006 Construction and real estate 1,621 70 Services 1,188 2,561 Wholesale and retail 4,614 13,396 Transportation and communications 771 201 Other industries — 130 Individuals 1,366 904 Total domestic 11,361 19,268 Foreign: Total foreign 30 4,588 Total 11,391 23,856
Age Analysis of Past Due Loans	The table below presents an analysis of the age of the recorded investment in loans that are past due at March 31, 2017 and September 30, 2017: 30-59 days 60-89 days 90 days or Total past Current Total (in millions of yen) March 31, 2017 Domestic: Manufacturing 1,938 360 7,767 10,065 8,730,216 8,740,281 Construction and real estate 2,818 947 32,523 36,288 7,617,728 7,654,016 Services 917 217 5,914 7,048 4,752,177 4,759,225 Wholesale and retail 1,330 2,834 5,585 9,749 5,132,254 5,142,003 Transportation and communications 384 322 1,859 2,565 3,487,850 3,490,415 Banks and other financial institutions — — — — 4,006,401 4,006,401 Government and public institutions — — — — 8,532,246 8,532,246 Other industries — — 69 69 4,427,280 4,427,349 Individuals 32,995 12,291 34,846 80,132 10,824,472 10,904,604 Total domestic 40,382 16,971 88,563 145,916 57,510,624 57,656,540 Foreign: Total foreign 546 216 95,719 96,481 24,686,560 24,783,041 Total 40,928 17,187 184,282 242,397 82,197,184 82,439,581 September 30, 2017 Domestic: Manufacturing 1,504 289 8,545 10,338 8,516,305 8,526,643 Construction and real estate 1,006 940 27,869 29,815 7,679,430 7,709,245 Services 2,076 1,537 4,898 8,511 4,915,327 4,923,838 Wholesale and retail 1,842 997 3,803 6,642 5,116,534 5,123,176 Transportation and communications 76 85 7,502 7,663 3,406,047 3,413,710 Banks and other financial institutions — — — — 4,247,285 4,247,285 Government and public institutions — — — — 9,981,557 9,981,557 Other industries 40 — 25 65 4,502,466 4,502,531 Individuals 31,787 11,185 34,554 77,526 10,582,762 10,660,288 Total domestic 38,331 15,033 87,196 140,560 58,947,713 59,088,273 Foreign: Total foreign 848 462 73,898 75,208 24,864,765 24,939,973 Total 39,179 15,495 161,094 215,768 83,812,478 84,028,246

Allowance for loan losses (Tabl

Allowance for loan losses (Tables)	6 Months Ended
	Sep. 30, 2017
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 loan losses by portfolio segment for the six months ended September 30, 2016 and 2017 are shown below: Corporate Retail Other Total (in millions of yen) Six months ended September 30, 2016 Balance at beginning of period 367,739 44,221 39,287 451,247 Provision (credit) for loan losses 9,123 (7,983 ) (571 ) 569 Charge-offs (10,332 ) (1,016 ) (3,812 ) (15,160 ) Recoveries 8,877 4,725 2,139 15,741 Net charge-offs (1,455 ) 3,709 (1,673 ) 581 Others (Note) (10,404 ) — (4,813 ) (15,217 ) Balance at end of period 365,003 39,947 32,230 437,180 Six months ended September 30, 2017 Balance at beginning of period 407,327 36,923 35,423 479,673 Provision (credit) for loan losses (109,379 ) (6,469 ) (2,114 ) (117,962 ) Charge-offs (17,366 ) (745 ) (3,107 ) (21,218 ) Recoveries 6,447 315 1,247 8,009 Net charge-offs (10,919 ) (430 ) (1,860 ) (13,209 ) Others (Note) 2,552 — (585 ) 1,967 Balance at end of period 289,581 30,024 30,864 350,469 Note: Others includes primarily foreign exchange translation. The table below presents Allowance for loan losses and loans outstanding by portfolio segment disaggregated on the basis of impairment method at March 31, 2017 and September 30, 2017: Corporate Retail Other Total (in millions of yen) March 31, 2017 Allowance for loan losses 407,327 36,923 35,423 479,673 of which individually evaluated for impairment 272,714 2,922 13,306 288,942 of which collectively evaluated for impairment 134,613 34,001 22,117 190,731 Loans (Note) 61,120,654 11,722,726 9,596,201 82,439,581 of which individually evaluated for impairment 772,647 23,422 65,075 861,144 of which collectively evaluated for impairment 60,348,007 11,699,304 9,531,126 81,578,437 September 30, 2017 Allowance for loan losses 289,581 30,024 30,864 350,469 of which individually evaluated for impairment 170,509 2,761 7,248 180,518 of which collectively evaluated for impairment 119,072 27,263 23,616 169,951 Loans (Note) 60,727,073 11,432,376 11,868,797 84,028,246 of which individually evaluated for impairment 673,081 22,734 61,318 757,133 of which collectively evaluated for impairment 60,053,992 11,409,642 11,807,479 83,271,113 Note: Amounts represent loan balances before deducting unearned income and deferred loan fees.

Other assets and liabilities (T

Other assets and liabilities (Tables)	6 Months Ended
	Sep. 30, 2017
Details of Other Assets and Liabilities	The following table sets forth the details of other assets and liabilities at March 31, 2017 and September 30, 2017: March 31, 2017 September 30, 2017 (in millions of yen) Other assets: Accounts receivable from brokers, dealers and customers for securities transactions 1,564,295 2,000,669 Collateral provided for derivative transactions 973,404 1,110,240 Prepaid pension cost 682,592 707,464 Margins provided for futures contracts 276,398 363,325 Miscellaneous receivables 324,135 294,262 Security deposits 122,858 127,302 Loans held for sale 26,689 20,546 Other 1,021,958 1,484,483 Total 4,992,329 6,108,291 Other liabilities: Accounts payable to brokers, dealers and customers for securities transactions 1,400,141 2,710,819 Guaranteed trust principal 683,324 714,801 Collateral accepted for derivative transactions 671,691 568,881 Miscellaneous payables 481,809 456,138 Margins accepted for futures contracts 307,066 363,221 Unearned income 134,666 130,480 Factoring amounts owed to customers 53,488 22,810 Other 1,294,340 1,088,413 Total 5,026,525 6,055,563

Preferred and common stock (Tab

Preferred and common stock (Tables)	6 Months Ended
	Sep. 30, 2017
Preferred stock
Schedule of Stock by Class	The composition of preferred stock at March 31, 2017 and September 30, 2017 is as follows: Class of stock March 31, 2017 September 30, 2017 Authorized Issued Authorized Issued (number of shares) Class XI preferred stock 914,752,000 — — — First series class XIV preferred stock (1) 900,000,000 — 900,000,000 — Second series class XIV preferred stock (1) 900,000,000 — 900,000,000 — Third series class XIV preferred stock (1) 900,000,000 — 900,000,000 — Fourth series class XIV preferred stock (1) 900,000,000 — 900,000,000 — First series class XV preferred stock (2) 900,000,000 — 900,000,000 — Second series class XV preferred stock (2) 900,000,000 — 900,000,000 — Third series class XV preferred stock (2) 900,000,000 — 900,000,000 — Fourth series class XV preferred stock (2) 900,000,000 — 900,000,000 — First series class XVI preferred stock (3) 1,500,000,000 — 1,500,000,000 — Second series class XVI preferred stock (3) 1,500,000,000 — 1,500,000,000 — Third series class XVI preferred stock (3) 1,500,000,000 — 1,500,000,000 — Fourth series class XVI preferred stock (3) 1,500,000,000 — 1,500,000,000 — Total 4,214,752,000 — 3,300,000,000 — Notes: (1) The total number of authorized shares from first to fourth series class XIV preferred stock shall not exceed 900,000,000. (2) The total number of authorized shares from first to fourth series class XV preferred stock shall not exceed 900,000,000. (3) The total number of authorized shares from first to fourth series class XVI preferred stock shall not exceed 1,500,000,000.

Dividends (Tables)

Dividends (Tables)	6 Months Ended
	Sep. 30, 2017
Dividends on Preferred Stock and Common Stock	The following table shows dividends on preferred stock and common stock during the six months ended September 30, 2016 and 2017: September 30, 2016 Cash dividends Class of stock Per share In aggregate (in yen) (in millions of yen) Eleventh series class XI preferred stock 10 989 Common stock 3.75 93,839 Total 94,828 September 30, 2017 Cash dividends Class of stock Per share In aggregate (in yen) (in millions of yen) Common stock 3.75 95,174

Accumulated other comprehensi38

Accumulated other comprehensive income (Tables)	6 Months Ended
	Sep. 30, 2017
Changes in Each Component of Accumulated Other Comprehensive Income, Net of Tax	Changes in each component of Accumulated other comprehensive income, net of tax (“AOCI”) for the six months ended September 30, 2016 and 2017 are as follows: Six months ended September 30, 2016 2017 (in millions of yen) AOCI, balance at beginning of period, previously reported 1,469,308 1,521,163 Cumulative effect of change in accounting principles (Note 17) 330 — AOCI, balance at beginning of period, adjusted 1,469,638 1,521,163 Net unrealized gains (losses) on available-for-sale Balance at beginning of period, previously reported 1,409,459 1,461,302 Cumulative effect of change in accounting principles (Note 17) (85 ) — Balance at beginning of period, adjusted 1,409,374 1,461,302 Unrealized holding gains (losses) during period (49,362 ) 247,493 Less: reclassification adjustments for losses (gains) included in net income (86,761 ) (78,659 ) Change during period (136,123 ) 168,834 Balance at end of period 1,273,251 1,630,136 Foreign currency translation adjustments: Balance at beginning of period, previously reported 6,310 (5,535 ) Cumulative effect of change in accounting principles (Note 17) 415 — Balance at beginning of period, adjusted 6,725 (5,535 ) Foreign currency translation adjustments during period (59,893 ) (4,322 ) Less: reclassification adjustments for losses (gains) included in net income — — Change during period (59,893 ) (4,322 ) Balance at end of period (53,168 ) (9,857 ) Pension liability adjustments: Balance at beginning of period 53,539 65,396 Unrealized gains (losses) during period 533 32 Less: reclassification adjustments for losses (gains) included in net income 144 140 Change during period 677 172 Balance at end of period 54,216 65,568 Total other comprehensive income (loss), net of tax attributable to MHFG shareholders (195,339 ) 164,684 AOCI, balance at end of period 1,274,299 1,685,847
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, 2017: Six months ended September 30, 2017 Before tax (1) Tax effect (2) Net of tax before Net of tax attributable to (2) Net of tax attributable to shareholders (in millions of yen) Amounts reclassified out of AOCI into net income: Affected line items in the consolidated statements of income: Net unrealized gains (losses) on available-for-sale 113,819 (35,053 ) 78,766 (107 ) 78,659 Investment gains (losses)—net Pension liability adjustments (233 ) 96 (137 ) (3 ) (140 ) Salaries and employee benefits Total 113,586 (34,957 ) 78,629 (110 ) 78,519 Notes: (1) The amounts in the Before tax column are recorded in each account presented under the heading “Affected line items in the consolidated statements of income”. (2) The amounts in the Tax effect column and Net of tax attributable to noncontrolling interests column are recorded in Income tax expense and Net income (loss) attributable to noncontrolling interests in the consolidated statements of income, respectively.

Regulatory matters (Tables)

Regulatory matters (Tables)	6 Months Ended
	Sep. 30, 2017
Capital Adequacy Ratios of MHFG, MHBK, and MHTB Calculated in Accordance with Japanese GAAP and Guidelines Established by Financial Services Agency	Capital adequacy ratios of MHFG, MHBK, and MHTB as of March 31, 2017 and September 30, 2017 calculated in accordance with Japanese GAAP and the guidelines established by the Financial Services Agency are set forth in the following table: March 31, 2017 September 30, 2017 Amount Ratio Amount Ratio (in billions of yen, except percentages) Consolidated: MHFG: Common Equity Tier 1 capital: Required (Note) 3,857 6.25 3,856 6.25 Actual 7,002 11.34 7,281 11.80 Tier 1 capital: Required (Note) 4,783 7.75 4,781 7.75 Actual 8,212 13.30 9,005 14.59 Total risk-based capital: Required (Note) 6,017 9.75 6,015 9.75 Actual 10,051 16.28 10,947 17.74 MHBK: Common Equity Tier 1 capital: Required 2,541 4.50 2,525 4.50 Actual 6,304 11.16 6,604 11.76 Tier 1 capital: Required 3,388 6.00 3,366 6.00 Actual 7,536 13.34 8,349 14.87 Total risk-based capital: Required 4,517 8.00 4,489 8.00 Actual 9,149 16.20 10,193 18.16 MHTB: Common Equity Tier 1 capital: Required 112 4.50 110 4.50 Actual 466 18.73 487 19.95 Tier 1 capital: Required 149 6.00 146 6.00 Actual 466 18.73 487 19.95 Total risk-based capital: Required 199 8.00 195 8.00 Actual 485 19.47 505 20.68 Non-consolidated: MHBK: Common Equity Tier 1 capital: Required 2,432 4.50 2,417 4.50 Actual 6,057 11.20 6,347 11.81 Tier 1 capital: Required 3,243 6.00 3,223 6.00 Actual 7,316 13.53 8,101 15.08 Total risk-based capital: Required 4,324 8.00 4,298 8.00 Actual 8,938 16.53 9,949 18.52 MHTB: Common Equity Tier 1 capital: Required 113 4.50 110 4.50 Actual 475 18.98 494 20.28 Tier 1 capital: Required 150 6.00 146 6.00 Actual 475 18.98 494 20.28 Total risk-based capital: Required 200 8.00 195 8.00 Actual 493 19.70 511 20.99 Note: The required ratios disclosed above, at March 31, 2017 and September 30, 2017, include the transitional capital conservation buffer of 1.25% and the transitional additional loss absorbency requirements for global systemically important banks (“G-SIBs”) (“D-SIBs”)

Earnings per common share (Tabl

Earnings per common share (Tables)	6 Months Ended
	Sep. 30, 2017
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, 2016 and 2017: Six months ended 2016 2017 (in millions of yen) Net income: Net income attributable to MHFG shareholders 379,558 372,549 Less: Net income attributable to preferred shareholders — — Net income attributable to common shareholders 379,558 372,549 Effect of dilutive securities: Convertible preferred stock — — Net income attributable to common shareholders after assumed conversions 379,558 372,549 Six months ended 2016 2017 (thousands of shares) Shares: Weighted average common shares outstanding 25,204,801 25,366,347 Effect of dilutive securities: Convertible preferred stock (Note) 165,533 — Stock options 11,997 7,933 Weighted average common shares after assumed conversions 25,382,331 25,374,280 Six months ended 2016 2017 (in yen) Amounts per common share: Basic net income per common share 15.06 14.69 Diluted net income per common share 14.95 14.68 Note: The number of common shares after assumed conversion of the convertible preferred stock is based on the applicable conversion prices.

Income taxes (Tables)

Income taxes (Tables)	6 Months Ended
	Sep. 30, 2017
Components of Income Tax Expense	The following table presents the components of Income tax expense for the six months ended September 30, 2016 and 2017: Six months ended September 30, 2016 2017 (in millions of yen) Current tax expense 102,390 99,238 Deferred tax expense (benefit) (27,875 ) 20,095 Total income tax expense 74,515 119,333
Detailed Amounts of Tax Effects of Items Recorded Directly in Equity	The detailed amounts recorded directly in Equity are as follows: Six months ended September 30, 2016 2017 (in millions of yen) Net unrealized gains (losses) on available-for-sale Unrealized gains (losses) (21,562 ) 105,819 Less: reclassification adjustments (38,351 ) (35,053 ) Total (59,913 ) 70,766 Foreign currency translation adjustments: Unrealized gains (losses) (126 ) — Less: reclassification adjustments — — Total (126 ) — Pension liability adjustments: Unrealized gains (losses) 239 11 Less: reclassification adjustments 87 96 Total 326 107 Total tax effect before allocation to noncontrolling interests (59,713 ) 70,873

Pension and other employee be42

Pension and other employee benefit plans (Tables)	6 Months Ended
	Sep. 30, 2017
Summary of 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, 2016 and 2017: Six months ended September 30, 2016 2017 (in millions of yen) Service cost-benefits earned during the period 22,219 21,643 Interest costs on projected benefit obligations 2,716 3,609 Expected return on plan assets (17,860 ) (17,353 ) Amortization of prior service benefits (97 ) 102 Amortization of net actuarial loss (gain) 385 214 Special termination benefits 1,744 2,128 Net periodic benefit cost 9,107 10,343

Derivative financial instrume43

Derivative financial instruments (Tables)	6 Months Ended
	Sep. 30, 2017
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, 2017 and September 30, 2017. The fair values of derivatives are presented on a gross basis and 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, 2017 Notional amount (1) Designated Not designated Designated Not designated (in billions of yen) Interest rate contracts 961,518 — 8,506 — 8,473 Foreign exchange contracts 167,698 2 2,743 — 2,611 Equity-related contracts 4,177 — 134 5 224 Credit-related contracts 3,696 — 35 — 36 Other contracts 360 — 23 — 22 Total 1,137,449 2 11,441 5 11,366 Fair value Derivative receivables (2) Derivative payables (2) September 30, 2017 Notional amount (1) Designated Not designated Designated Not designated (in billions of yen) Interest rate contracts 956,180 — 7,662 — 7,658 Foreign exchange contracts 169,964 — 2,484 5 2,393 Equity-related contracts 5,396 — 151 14 258 Credit-related contracts 3,273 — 29 — 31 Other contracts 388 — 18 — 17 Total 1,135,201 — 10,344 19 10,357 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, 2017 and September 30, 2017: March 31, 2017 September 30, 2017 Notional amount Fair value Notional amount Fair value (in billions of yen) Credit protection written: Investment grade 1,546 21 1,371 23 Non-investment 298 1 202 1 Total 1,844 22 1,573 24 Credit protection purchased 1,994 (23 ) 1,727 (26 ) 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, 2017 and September 30, 2017: Maximum payout/Notional amount March 31, 2017 September 30, 2017 (in billions of yen) One year or less 507 406 After one year through five years 1,020 926 After five years 317 241 Total 1,844 1,573 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, 2017 and September 30, 2017: March 31, 2017 September 30, 2017 (in billions of yen) Aggregate fair value of derivative instruments with credit-risk-related contingent features in net liability positions 698 755 Collateral provided to counterparties in the normal course of business 658 729 Amount required to be posted as collateral or settled immediately if credit-risk-related contingent features were triggered 40 26
Designated as Hedging Instrument | Fair Value Hedging
Schedule of Derivative Instruments, Gain (Loss) in Statement of Financial Performance	The following table summarizes gains and losses information related to fair value hedges for the six months ended September 30, 2016 and 2017: Gains (losses) recorded in income Six months ended September 30, 2016 Derivatives Hedged Hedge Net gain (loss) excluded (in millions of yen) Equity-related contracts 6,002 (7,807 ) — (1,805 ) Total 6,002 (7,807 ) — (1,805 ) Gains (losses) recorded in income Six months ended September 30, 2017 Derivatives Hedged Hedge Net gain (loss) excluded (in millions of yen) Equity-related contracts (22,493 ) 20,208 — (2,285 ) Total (22,493 ) 20,208 — (2,285 )
Designated as Hedging Instrument | Net Investment Hedging
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, 2016 and 2017: Gains (losses) recorded in income and other comprehensive income (“OCI”) for six months ended September 30, 2016 2017 Effective portion Ineffective portion Effective portion Ineffective portion (in millions of yen) Financial instruments hedging foreign exchange risk 107,528 890 3,487 196 Total 107,528 890 3,487 196 Note: No amount related to the effective portion of net investment hedges was reclassified from Accumulated other comprehensive income to earnings for the six months ended September 30, 2016 and 2017, respectively.
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, 2016 and 2017: Gains (losses) recorded in income 2016 2017 (in millions of yen) Interest rate contracts 80,040 26,648 Foreign exchange contracts 11,173 (4,511 ) Equity-related contracts (1) 11,049 (41,869 ) Credit-related contracts (2) (4,827 ) (3,371 ) Other contracts 564 494 Total 97,999 (22,609 ) Notes: (1) The net gain (loss) excluded from the assessment of the effectiveness of fair value hedges is not included in the above table. (2) Amounts include the net gain (loss) of ¥(5,698) million and ¥(273) million on the credit derivatives hedging the credit risk of loans during the six months ended September 30, 2016 and 2017, respectively.

Commitments and contingencies (

Commitments and contingencies (Tables)	6 Months Ended
	Sep. 30, 2017
Summary of Maximum Potential Amount of Future Payments under Guarantees	The table below summarizes the maximum potential amount of future payments by type of guarantee at March 31, 2017 and September 30, 2017. 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, September 30, (in billions of yen) Performance guarantees 2,243 2,363 Guarantees on loans 278 259 Guarantees on securities 175 174 Other guarantees 1,823 1,933 Guarantees for the repayment of trust principal 730 642 Liabilities of trust accounts 15,177 15,288 Derivative financial instruments 14,415 13,080
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, 2017 and September 30, 2017: March 31, September 30, (in billions of yen) Commitments to extend credit (Note) 76,678 77,100 Commercial letters of credit 522 622 Total 77,200 77,722 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, 2017 and September 30, 2017: March 31, September 30, (in billions of yen) Investment grade 3,477 3,808 Non-investment 1,042 921 Total 4,519 4,729 Note: Investment grade in the internal rating scale generally corresponds to BBB- or above in the external rating scale.

Variable interest entities an45

Variable interest entities and securitizations (Tables)	6 Months Ended
	Sep. 30, 2017
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, as of March 31, 2017 and September 30, 2017: Consolidated VIEs Significant March 31, 2017 Consolidated assets Total assets Maximum (in billions of yen) Asset-backed commercial paper/loan programs 2,031 — — Asset-backed securitizations 629 108 11 Investments in securitization products 375 445 154 Investment funds 2,188 3,895 463 Trust arrangements and other 23 — — Total 5,246 4,448 628 Consolidated VIEs Significant September 30, 2017 Consolidated assets Total assets Maximum (in billions of yen) Asset-backed commercial paper/loan programs 1,863 — — Asset-backed securitizations 626 66 11 Investments in securitization products 374 136 80 Investment funds 2,249 4,281 614 Trust arrangements and other 22 — — Total 5,134 4,483 705
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, 2017 and September 30, 2017: Assets on balance sheets related to unconsolidated VIEs: March 31, 2017 September 30, 2017 (in billions of yen) Trading account assets 85 100 Investments 254 386 Loans 237 168 Total 576 654 Liabilities on balance sheets and maximum exposure to loss related to unconsolidated VIEs: March 31, 2017 September 30, 2017 (in billions of yen) Payables under securities lending transactions 31 37 Trading account liabilities 1 1 Total 32 38 Maximum exposure to loss (Note) 628 705 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

Fee and commission income (Tabl

Fee and commission income (Tables)	6 Months Ended
	Sep. 30, 2017
Details of Fee and Commission Income	Details of Fee and commission income for the six months ended September 30, 2016 and 2017 are as follows: Six months ended September 30, 2016 2017 (in millions of yen) Securities-related business 75,145 85,897 Deposits and lending business 85,340 65,081 Remittance business 53,858 54,166 Asset management business 29,548 50,322 Trust fees 23,134 25,966 Fees for other customer services 125,437 119,799 Total 392,462 401,231

Fair value (Tables)

Fair value (Tables)	6 Months Ended
	Sep. 30, 2017
Summary of Assets and Liabilities Measured at Fair Value on a Recurring Basis, Including Fair Value Option Elected	Assets and liabilities measured at fair value on a recurring basis at March 31, 2017 and September 30, 2017, including those for which the MHFG Group has elected the fair value option, are summarized below: March 31, 2017 Level 1 Level 2 Level 3 Assets/ (in billions of yen) Assets: Trading securities (1) Japanese government bonds 1,485 23 — 1,508 Japanese local government bonds — 69 — 69 U.S. Treasury bonds and federal agency securities 2,883 80 — 2,963 Other foreign government bonds 1,127 457 — 1,584 Agency mortgage-backed securities 1,335 638 — 1,973 Residential mortgage-backed securities — — 15 15 Commercial mortgage-backed securities — 3 — 3 Certificates of deposit and commercial paper — 554 — 554 Corporate bonds and other 3 1,449 1,052 2,504 Equity securities 1,661 20 23 1,704 Trading securities measured at net asset value (2) 678 Derivatives: Interest rate contracts 37 8,442 27 8,506 Foreign exchange contracts 28 2,709 8 2,745 Equity-related contracts 31 89 14 134 Credit-related contracts — 33 2 35 Other contracts 1 11 11 23 Available-for-sale Japanese government bonds 9,543 720 — 10,263 Japanese local government bonds — 284 — 284 U.S. Treasury bonds and federal agency securities 1,144 — — 1,144 Other foreign government bonds 346 589 — 935 Agency mortgage-backed securities 134 709 — 843 Residential mortgage-backed securities — 67 77 144 Commercial mortgage-backed securities — — 224 224 Japanese corporate bonds and other debt securities — 1,834 174 2,008 Foreign corporate bonds and other debt securities — 801 110 911 Equity securities (marketable) 3,717 84 — 3,801 Other investments — — 37 37 Total assets measured at fair value on a recurring basis 23,475 19,665 1,774 45,592 Liabilities: Trading securities sold, not yet purchased 1,993 228 — 2,221 Derivatives: Interest rate contracts 46 8,426 1 8,473 Foreign exchange contracts 20 2,591 — 2,611 Equity-related contracts 129 61 39 229 Credit-related contracts — 34 2 36 Other contracts 1 10 11 22 Long-term debt (3) — 903 593 1,496 Total liabilities measured at fair value on a recurring basis 2,189 12,253 646 15,088 September 30, 2017 Level 1 Level 2 Level 3 Assets/ (in billions of yen) Assets: Trading securities (1) Japanese government bonds 3,012 29 — 3,041 Japanese local government bonds — 48 — 48 U.S. Treasury bonds and federal agency securities 3,832 295 — 4,127 Other foreign government bonds 1,368 449 — 1,817 Agency mortgage-backed securities 1,264 742 — 2,006 Residential mortgage-backed securities — — 14 14 Certificates of deposit and commercial paper — 708 — 708 Corporate bonds and other 9 1,929 1,086 3,024 Equity securities 1,625 — 22 1,647 Trading securities measured at net asset value (2) 681 Derivatives: Interest rate contracts 40 7,600 22 7,662 Foreign exchange contracts 20 2,458 6 2,484 Equity-related contracts 40 93 18 151 Credit-related contracts — 27 2 29 Other contracts 2 7 9 18 Available-for-sale Japanese government bonds 8,926 732 — 9,658 Japanese local government bonds — 254 — 254 U.S. Treasury bonds and federal agency securities 850 — — 850 Other foreign government bonds 364 608 — 972 Agency mortgage-backed securities 161 730 — 891 Residential mortgage-backed securities — 69 68 137 Commercial mortgage-backed securities — — 257 257 Japanese corporate bonds and other debt securities — 1,785 165 1,950 Foreign corporate bonds and other debt securities — 793 97 890 Equity securities (marketable) 4,236 57 — 4,293 Other investments — — 39 39 Total assets measured at fair value on a recurring basis 25,749 19,413 1,805 47,648 Liabilities: Trading securities sold, not yet purchased 2,296 269 4 2,569 Derivatives: Interest rate contracts 39 7,618 1 7,658 Foreign exchange contracts 16 2,382 — 2,398 Equity-related contracts 161 67 44 272 Credit-related contracts — 29 2 31 Other contracts 2 7 8 17 Long-term debt (3) — 1,381 563 1,944 Total liabilities measured at fair value on a recurring basis 2,514 11,753 622 14,889 Notes: (1) Trading securities include foreign currency denominated securities for which the MHFG Group elected the fair value option. (2) 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, 2017 and September 30, 2017 were ¥33 billion and ¥29 billion, respectively. (3) Amounts represent items for which the Group elected the fair value option.
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, 2016 and 2017: Six months ended September 30, 2016 April 1, Gains Gains Transfers Transfers Purchases Sales Issuances Settle- September 30, Change in (losses) (6) (in billions of yen) Assets: Trading securities: Residential mortgage-backed securities 21 — (2) — — — — — — (4 ) 17 — Commercial mortgage-backed securities 2 — (2) — — — — — — (2 ) — — Corporate bonds and 720 (53 ) (2) — 280 (2 ) 343 (241 ) — (71 ) 976 (39 ) Equity securities 21 4 (2) — — — — (7 ) — — 18 4 Derivatives, net (1) Interest rate contracts 26 (4 ) (2) — — — — — — — 22 (3 ) Foreign exchange contracts 7 6 (2) — — — — — — (7 ) 6 — Equity-related contracts 5 (13 ) (2) — — — — — — (2 ) (10 ) (19 ) Credit-related contracts (1 ) 1 (2) — — — — — — — — — Other contracts 1 — (2) — — — — — — — 1 — Available-for-sale Residential mortgage-backed securities 123 — (3) — (4) — — — (1 ) — (22 ) 100 — Commercial mortgage-backed securities 187 — (3) — (4) — — 20 — — (9 ) 198 — Japanese corporate bonds and other debt securities 174 — (3) 22 (4) — — 1 (4 ) — (17 ) 176 — Foreign corporate bonds and other debt securities 108 1 (3) (7 ) (4) — — 10 — — (5 ) 107 — Other investments 42 (3 ) (3) — — — 11 — — (13 ) 37 (1 ) Liabilities: Trading securities sold, not yet purchased — — (2) — 1 — (32 ) 32 — — 1 — Long-term debt 623 9 (5) — — (12 ) — — 147 (158 ) 591 5 Six months ended September 30, 2017 April 1, Gains Gains Transfers Transfers Purchases Sales Issuances Settle- September 30, Change in (losses) (6) (in billions of yen) Assets: Trading securities: Residential mortgage-backed securities 15 — (2) — — — — — — (1 ) 14 — Corporate bonds and 1,052 18 (2) — 123 (240 ) 562 (276 ) — (153 ) 1,086 20 Equity securities 23 (1 ) (2) — — — — — — — 22 (1 ) Derivatives, net (1) Interest rate contracts 26 (6 ) (2) — — — — — — 1 21 (6 ) Foreign exchange contracts 8 (2 ) (2) — — — — — — — 6 (2 ) Equity-related contracts (25 ) (7 ) (2) — — — — — — 6 (26 ) (8 ) Other contracts — — (2) — — — — — — 1 1 — Available-for-sale Residential mortgage-backed securities 77 — (3) — (4) — — 1 — — (10 ) 68 — Commercial mortgage-backed securities 224 — (3) — (4) — — 40 (7 ) — — 257 — Japanese corporate bonds and other debt securities 174 (1 ) (3) (3 ) (4) — — 11 — — (16 ) 165 (1 ) Foreign corporate bonds and other debt securities 110 — (3) 1 (4) 15 (29 ) — — — — 97 — Other investments 37 — (3) — — — 12 — — (10 ) 39 — Liabilities: Trading securities sold, not yet purchased — — (2) — — — (57 ) 61 — — 4 — Long-term debt 593 (13 ) (5) — 1 (10 ) — — 47 (81 ) 563 (14 ) 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, Foreign exchange gains (losses)—net or Other noninterest income (expenses). (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 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, 2016 and 2017.
Quantitative Information about Significant Unobservable Inputs Related to Material Classes of Level 3 Assets and Liabilities	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, 2017 and September 30, 2017: March 31, 2017 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 92 Discounted cash flow Price-based Prepayment rate Recovery rate Discount margin 0% -18% 0% - 1% 15bps - 170bps 7% Commercial 224 Discounted cash flow Discount margin 4bps - 205bps 28bps Corporate bonds and 1,336 Discounted cash flow Prepayment rate (1) (1) (1) (1) (2) 16% - 30% 1% - 2% 60% - 68% 8bps - 1,181bps 29% Derivatives, net: Interest rate 26 Internal valuation model (3) IR – IR correlation (4) 23% - 100% Foreign exchange 8 Internal valuation model (3) FX – IR correlation FX – FX correlation (4) 5% - 52% 55% - 55% 0% - 63% Equity-related (25 ) Internal valuation model (3) Equity – IR correlation 25% - 25% 6% - 59% Credit-related — Internal valuation model (3) Default rate Credit correlation 0% - 5% 30% - 100% Long-term debt 593 Internal valuation model (3) IR – IR correlation Credit correlation 23% - 100% 55% - 55% 0% - 3% 33% - 100% September 30, 2017 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 82 Discounted cash flow Prepayment rate Recovery rate 3% - 17% 0% - 1% 100% - 100% 7% Commercial 257 Discounted cash flow Discount margin 2bps - 93bps 27bps Corporate bonds and other debt 1,348 Discounted cash flow Prepayment rate (1) (1) (1) (1) (2) 22% - 39% 1% - 2% 60% - 68% 16bps - 1,179bps 39% Derivatives, net: Interest rate 21 Internal valuation model (3) IR – IR correlation (4) 23% - 100% Foreign exchange contracts 6 Internal valuation model (3) FX – IR correlation (4) 5% - 54% 59% - 59% 0% - 63% Equity-related (26 ) Internal valuation model (3) Equity – IR correlation Equity volatility 25% - 25% Credit-related — Internal valuation model (3) Default rate Credit correlation 0% - 3% 26% - 100% Long-term debt 563 Internal valuation model (3) IR – IR correlation FX – IR correlation Credit correlation 23% - 100% 59% - 59% 0% - 2% 32% - 100% 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) Weighted averages are calculated by weighting each input by the relative fair value of the respective financial instruments.
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, 2017 and September 30, 2017: March 31, 2017 Total Level 1 Level 2 Level 3 Aggregate cost (in billions of yen) Assets: Loans 124 — — 124 194 Loans held-for-sale 7 — 7 — 8 Other investments 7 6 — 1 11 Premises and equipment—net 7 — 6 1 11 Total assets measured at fair value on a nonrecurring basis 145 6 13 126 224 September 30, 2017 Total Level 1 Level 2 Level 3 Aggregate cost (in billions of yen) Assets: Loans 120 — — 120 183 Loans held-for-sale 5 — 5 — 8 Other investments — — — — 1 Total assets measured at fair value on a nonrecurring basis 125 — 5 120 192
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 and fair values at March 31, 2017 and September 30, 2017, of certain financial instruments, excluding financial instruments which are carried at fair value on a recurring basis and those outside the scope of ASC 825 such as equity method investments as defined in ASC 323, “Investments—Equity Method and Joint Ventures” (“ASC 323”) and lease contracts as defined in ASC 840, “Leases” (“ASC 840”): March 31, 2017 Carrying Estimated fair value Total Level 1 Level 2 Level 3 (in billions of yen) Financial assets: Cash and due from banks, call loans and funds sold, and receivables under resale agreements and securities borrowing transactions 60,943 60,943 1,063 59,880 — Investments 3,817 3,846 3,846 — — Loans, net of allowance for loan losses (Note) 81,662 82,696 — — 82,696 Financial liabilities: Noninterest-bearing deposits, call money and funds purchased, and payables under repurchase agreements and securities lending transactions 42,205 42,205 20,544 21,661 — Interest-bearing deposits 110,125 110,124 56,738 53,386 — Due to trust accounts 4,123 4,123 — 4,123 — Other short-term borrowings 1,477 1,477 — 1,477 — Long-term debt 13,009 13,078 — 12,120 958 September 30, 2017 Carrying Estimated fair value Total Level 1 Level 2 Level 3 (in billions of yen) Financial assets: Cash and due from banks, call loans and funds sold, and receivables under resale agreements and securities borrowing transactions 65,291 65,291 909 64,382 — Investments 3,127 3,148 3,148 — — Loans, net of allowance for loan losses (Note) 83,401 84,306 — — 84,306 Financial liabilities: Noninterest-bearing deposits, call money and funds purchased, and payables under repurchase agreements and securities lending transactions 46,373 46,373 21,957 24,416 — Interest-bearing deposits 114,675 114,668 57,802 56,866 — Due to trust accounts 3,999 3,999 — 3,999 — Other short-term borrowings 931 931 — 931 — Long-term debt 12,157 12,258 — 11,274 984 Note: Loans, net of allowance for loan losses include items measured at fair value on a nonrecurring basis.

Offsetting of financial asset48

Offsetting of financial assets and financial liabilities (Tables)	6 Months Ended
	Sep. 30, 2017
Information of Offsetting of Financial Assets and Financial Liabilities	The following table provides information about the offsetting of financial assets and financial liabilities at March 31, 2017 and September 30, 2017. The table includes derivatives, repurchase and resale agreements, and securities lending and borrowing transactions that are subject to enforceable master netting arrangements or similar agreements irrespective of whether or not they are offset on the Group’s consolidated balance sheets. Amounts not offset on ( 3 ) Gross amounts Gross amounts offset on the Net amounts presented on the (2) Financial instruments ( 4 ) Cash collateral Net (in billions of yen) March 31, 2017 Assets (1) Derivatives 10,608 — 10,608 (8,966 ) (620 ) 1,022 Receivables under resale agreements 8,698 — 8,698 (8,662 ) — 36 Receivables under securities borrowing transactions 3,127 — 3,127 (3,116 ) — 11 Total 22,433 — 22,433 (20,744 ) (620 ) 1,069 Liabilities (1) Derivatives 10,405 — 10,405 (8,866 ) (901 ) 638 Payables under repurchase agreements 17,446 — 17,446 (17,391 ) — 55 Payables under securities lending transactions 1,458 — 1,458 (1,455 ) — 3 Total 29,309 — 29,309 (27,712 ) (901 ) 696 September 30, 2017 Assets (1) Derivatives 9,806 — 9,806 (8,370 ) (504 ) 932 Receivables under resale agreements 9,162 — 9,162 (9,105 ) — 57 Receivables under securities borrowing transactions 3,192 — 3,192 (3,172 ) — 20 Total 22,160 — 22,160 (20,647 ) (504 ) 1,009 Liabilities (1) Derivatives 9,658 — 9,658 (8,120 ) (972 ) 566 Payables under repurchase agreements 18,453 — 18,453 (18,275 ) — 178 Payables under securities lending transactions 2,315 — 2,315 (2,277 ) — 38 Total 30,426 — 30,426 (28,672 ) (972 ) 782 Notes: (1) Amounts relating to master netting arrangements or similar agreements where the MHFG Group does not have the legal right of set-off over-the-counter OTC-cleared (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.

Repurchase agreements and sec49

Repurchase agreements and securities lending transactions accounted for as secured borrowings (Tables)	6 Months Ended
	Sep. 30, 2017
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, 2017 and September 30, 2017: Overnight and Up to 30 days 31-90 days Greater than 90 days Total (in billions of yen) March 31, 2017 Repurchase agreements 249 12,700 3,897 1,124 17,970 Securities lending transactions 320 1,359 — 240 1,919 Total 569 14,059 3,897 1,364 19,889 September 30, 2017 Repurchase agreements 534 13,199 4,596 1,193 19,522 Securities lending transactions 2,177 463 — 233 2,873 Total 2,711 13,662 4,596 1,426 22,395
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, 2017 and September 30, 2017: Repurchase Securities lending (in billions of yen) March 31, 2017 Japanese government bonds and Japanese local government bonds 1,127 1,152 Foreign government bonds and foreign agency mortgage-backed securities 15,782 375 Commercial paper and corporate bonds 294 47 Equity securities 578 320 Other 189 25 Total (Note) 17,970 1,919 September 30, 2017 Japanese government bonds and Japanese local government bonds 1,156 1,767 Foreign government bonds and foreign agency mortgage-backed securities 17,332 453 Commercial paper and corporate bonds 377 47 Equity securities 514 583 Other 143 23 Total (Note) 19,522 2,873 Note: Amounts exceeded the gross amounts recognized in Note 20 “Offsetting of financial assets and financial liabilities” by ¥985 billion and ¥1,627 billion, at March 31, 2017 and September 30, 2017, 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, 2017
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 each business segment’s net business profits with income before income tax expense under U.S. GAAP. Management does not use information on business segment’s assets to allocate resources and assess performance and has not prepared information on the segment’s assets. Accordingly, information on the segment’s assets is not available. MHFG (Consolidated) Six months ended September 30, 2016 Retail & Corporate & Global Global Asset Others (2)(3) Total (in billions of yen) Gross profits 348.0 215.2 183.4 333.6 24.4 (14.9 ) 1,089.7 General and administrative expenses 359.8 96.5 117.9 90.1 15.0 1.2 680.5 Equity in earnings (losses) of equity method investees—net 8.8 0.6 1.0 — (0.1 ) 1.0 11.3 Others — — — — — (17.3 ) (17.3 ) Net business profits (losses) (1) (3.0 ) 119.3 66.5 243.5 9.3 (32.4 ) 403.2 MHFG (Consolidated) Six months ended September 30, 2017 Retail & Corporate & Global Global Asset Others (2) Total (in billions of yen) Gross profits 343.0 192.0 160.2 236.2 24.9 3.5 959.8 General and administrative expenses 358.6 97.3 122.5 99.7 13.9 26.3 718.3 Equity in earnings (losses) of equity method investees—net 7.5 0.6 1.4 — 0.3 0.8 10.6 Others — — — — — (10.5 ) (10.5 ) Net business profits (losses) (1) (8.1 ) 95.3 39.1 136.5 11.3 (32.5 ) 241.6 Notes: (1) Net business profits is used in Japan as a measure of the profitability of core banking operations, and is defined as gross profits (or the sum of net interest income, fiduciary income, net fee and commission income, net trading income and net other operating income) less general and administrative expenses. Measurement of net business profits is required for regulatory reporting to the Financial Services Agency. (2) “Others” includes items which should be eliminated as internal transactions between each segment on a consolidated basis. (3) Beginning on April 1, 2017, new allocation methods for transactions between each segment and “Others” have been applied. Figures for the six months ended September 30, 2016 have been restated for the new allocation methods and “Equity in earnings (losses) of equity method investees—net” has been presented as a new item in connection with the use of the new allocation methods.
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 total net business profits under the internal management reporting systems for the six months ended September 30, 2016 and 2017 presented above to income before income tax expense shown on the consolidated statements of income is as follows: Six months ended September 30, 2016 2017 (in billions of yen) Net business profits 403.2 241.6 U.S. GAAP adjustments 14.8 95.7 (Provision) credit for loan losses (0.6 ) 118.0 Net gains (losses) related to equity investments 64.5 100.9 Non-recurring (4.7 ) (3.6 ) Gains on disposal of premises and equipment 3.5 4.6 (Provision) credit for losses on off-balance-sheet 7.9 4.2 Others—net (31.3 ) (48.5 ) Income before income tax expense 457.3 512.9

Business Combination - Addition

Business Combination - Additional Information (Detail) ¥ in Millions	Oct. 01, 2016JPY (¥)shares
MHAM
Business Acquisition [Line Items]
Interests exchanged	30.00%
Remeasurement gain recognized	¥ 23,829
Percentage of equity held by acquirer immediately before acquisition	30.00%
DIAM
Business Acquisition [Line Items]
Fair value of MHFG's equity interests in DIAM held before the business combination	¥ 72,106
Common shares of MHAM | shares	1,038,408
Fair value of total consideration transferred	¥ 28,842
Fair value, noncontrolling interest	43,264
Remeasurement gain recognized	¥ 56,226
Percentage of equity held by acquirer immediately before acquisition	50.00%
Asset Management One
Business Acquisition [Line Items]
Percentage of shareholding ratio based on voting rights	51.00%
Percentage of shareholding ratio based on economic interests	70.00%

Business Combination - (Summary

Business Combination - (Summary of Consideration Paid for DIAM, Amounts of Acquired Assets and Assumed Liabilities Recognized and Fair Value of Noncontrolling Interest at Acquisition Date in DIAM) (Detail) - JPY (¥) ¥ in Millions		Oct. 01, 2016	Sep. 30, 2017	Mar. 31, 2017
Recognized amounts of identifiable liabilities assumed:
Goodwill			¥ 95,196	¥ 95,176
DIAM
Consideration:
Equity instruments (1,038,408 common shares of MHAM)		¥ 28,842
Fair value of total consideration transferred		28,842
Fair value of equity interests in DIAM held by MHFG before the business combination		72,106
Business Combination, Consideration Transferred, Including Equity Interest in Acquiree Held Prior to Combination, Total		100,948
Recognized amounts of identifiable assets acquired:
Cash and due from banks		831
Interest-bearing deposits in other banks		12,873
Trading account assets		266
Investments		12,234
Premises and equipment-net		3,546
Accrued income		7,882
Intangible assets	[1]	53,037
Deferred tax assets		1,003
Other assets		2,208
Recognized amounts of identifiable liabilities assumed:
Trading account liabilities		304
Income taxes payable		918
Deferred taxes liabilities		16,238
Accrued expenses		5,392
Other liabilities		3,041
Total identifiable net assets		67,987
Goodwill		76,225
Noncontrolling interest in DIAM		43,264
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest		¥ 100,948
[1]	Note: Amount represents customer relationships subject to amortization, of which the weighted-average amortization period is 16.9 years.

Business Combination - (Summa53

Business Combination - (Summary of Consideration Paid for DIAM, Amounts of Acquired Assets and Assumed Liabilities Recognized and Fair Value of Noncontrolling Interest at Acquisition Date in DIAM) (Parenthetical) (Detail) - DIAM	Oct. 01, 2016shares
Business Acquisition [Line Items]
Common shares of MHAM	1,038,408
Customer relationships
Business Acquisition [Line Items]
Weighted-average amortization period	16 years 10 months 25 days

Investments (Amortized Cost, Gr

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, 2017	Mar. 31, 2017
Schedule of Investments [Line Items]
Amortized cost, available-for-sale securities		¥ 17,491,470	¥ 18,213,761
Gross unrealized gains, available-for-sale securities		2,696,135	2,376,615
Gross unrealized losses, available-for-sale securities		35,559	33,258
Fair value, available-for-sale securities		20,152,046	20,557,118
Amortized cost, held-to-maturity securities		3,127,486	3,817,360
Gross unrealized gains, held-to-maturity securities		28,162	37,289
Gross unrealized losses, held-to-maturity securities		7,852	7,931
Fair value, held-to-maturity securities		3,147,796	3,846,718
Debt securities | Agency mortgage-backed securities
Schedule of Investments [Line Items]
Amortized cost, available-for-sale securities	[1]	880,882	832,738
Gross unrealized gains, available-for-sale securities	[1]	13,981	15,500
Gross unrealized losses, available-for-sale securities	[1],[2]	4,313	5,441
Fair value, available-for-sale securities	[1]	890,550	842,797
Amortized cost, held-to-maturity securities	[3]	667,548	757,384
Gross unrealized gains, held-to-maturity securities	[3]	51	121
Gross unrealized losses, held-to-maturity securities	[3]	7,852	7,931
Fair value, held-to-maturity securities	[3]	659,747	749,574
Debt securities | Japanese government bonds
Schedule of Investments [Line Items]
Amortized cost, available-for-sale securities		9,672,831	10,256,512
Gross unrealized gains, available-for-sale securities		5,728	22,782
Gross unrealized losses, available-for-sale securities		20,335	16,408
Fair value, available-for-sale securities		9,658,224	10,262,886
Amortized cost, held-to-maturity securities		2,459,938	3,059,976
Gross unrealized gains, held-to-maturity securities		28,111	37,168
Fair value, held-to-maturity securities		2,488,049	3,097,144
Debt securities | Japanese local government bonds
Schedule of Investments [Line Items]
Amortized cost, available-for-sale securities		251,023	279,864
Gross unrealized gains, available-for-sale securities		3,007	4,841
Gross unrealized losses, available-for-sale securities		464	233
Fair value, available-for-sale securities		253,566	284,472
Debt securities | U.S. Treasury bonds and federal agency securities
Schedule of Investments [Line Items]
Amortized cost, available-for-sale securities		853,697	1,148,389
Gross unrealized gains, available-for-sale securities		153	10
Gross unrealized losses, available-for-sale securities		4,096	4,578
Fair value, available-for-sale securities		849,754	1,143,821
Debt securities | Other foreign government bonds
Schedule of Investments [Line Items]
Amortized cost, available-for-sale securities		971,933	933,942
Gross unrealized gains, available-for-sale securities		1,708	1,246
Gross unrealized losses, available-for-sale securities		820	236
Fair value, available-for-sale securities		972,821	934,952
Debt securities | Residential mortgage-backed securities
Schedule of Investments [Line Items]
Amortized cost, available-for-sale securities		135,814	142,879
Gross unrealized gains, available-for-sale securities		1,495	1,838
Gross unrealized losses, available-for-sale securities		512	558
Fair value, available-for-sale securities		136,797	144,159
Debt securities | Commercial mortgage-backed securities
Schedule of Investments [Line Items]
Amortized cost, available-for-sale securities		256,777	223,105
Gross unrealized gains, available-for-sale securities		1,063	1,092
Gross unrealized losses, available-for-sale securities		454	282
Fair value, available-for-sale securities		257,386	223,915
Debt securities | Japanese corporate bonds and other debt securities
Schedule of Investments [Line Items]
Amortized cost, available-for-sale securities	[4]	1,903,923	1,958,472
Gross unrealized gains, available-for-sale securities	[4]	47,293	52,046
Gross unrealized losses, available-for-sale securities	[4]	1,550	2,286
Fair value, available-for-sale securities	[4]	1,949,666	2,008,232
Debt securities | Foreign corporate bonds and other debt securities
Schedule of Investments [Line Items]
Amortized cost, available-for-sale securities	[5]	889,383	909,052
Gross unrealized gains, available-for-sale securities	[5]	2,437	3,377
Gross unrealized losses, available-for-sale securities	[5]	1,552	1,643
Fair value, available-for-sale securities	[5]	890,268	910,786
Equity securities (marketable)
Schedule of Investments [Line Items]
Amortized cost, available-for-sale securities		1,675,207	1,528,808
Gross unrealized gains, available-for-sale securities		2,619,270	2,273,883
Gross unrealized losses, available-for-sale securities		1,463	1,593
Fair value, available-for-sale securities		¥ 4,293,014	¥ 3,801,098
[1]	Agency mortgage-backed securities presented in this line consist of Japanese and Foreign agency mortgage-backed securities, of which the fair values were ¥708,557 million and ¥134,240 million, respectively, at March 31, 2017, and ¥729,895 million and ¥160,655 million, respectively, at September 30, 2017. 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.
[2]	Agency mortgage-backed securities presented in this line consist of Japanese and Foreign agency mortgage-backed securities, of which the fair values were ¥104,270 million and ¥134,118 million, respectively, at March 31, 2017, and ¥144,319 million and ¥160,546 million, respectively, at September 30, 2017. 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 certificates of deposit ("CDs"), of which the total fair values were ¥155,138 million at March 31, 2017, and ¥146,136 million at September 30, 2017.
[5]	Other debt securities presented in this line primarily consist of CDs and asset-backed securities ("ABS"), of which the total fair values were ¥258,059 million at March 31, 2017, and ¥290,380 million at September 30, 2017.

Investments (Amortized Cost, 55

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, 2017	Mar. 31, 2017
Schedule of Investments [Line Items]
Fair value, available-for-sale securities		¥ 20,152,046	¥ 20,557,118
Agency mortgage-backed securities | Debt securities
Schedule of Investments [Line Items]
Fair value, available-for-sale securities	[1]	890,550	842,797
Certificates of deposit ("CDs") and Asset-Backed Securities ("ABS") | Japanese government and corporate debt securities
Schedule of Investments [Line Items]
Fair value, available-for-sale securities		146,136	155,138
CDs, ABS, and collateral loan obligations ("CLO") | Foreign government and corporate debt securities
Schedule of Investments [Line Items]
Fair value, available-for-sale securities		290,380	258,059
Foreign agency mortgage-backed securities | Agency mortgage-backed securities | Debt securities
Schedule of Investments [Line Items]
Fair value, available-for-sale securities		160,655	134,240
Japanese agency mortgage-backed securities | Agency mortgage-backed securities | Debt securities
Schedule of Investments [Line Items]
Fair value, available-for-sale securities		¥ 729,895	¥ 708,557
[1]	Agency mortgage-backed securities presented in this line consist of Japanese and Foreign agency mortgage-backed securities, of which the fair values were ¥708,557 million and ¥134,240 million, respectively, at March 31, 2017, and ¥729,895 million and ¥160,655 million, respectively, at September 30, 2017. 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 and

Investments (Amortized Cost and Fair Value of Available-for-Sale and Held-to-Maturity Debt Securities by Contractual Maturity) (Detail) - JPY (¥) ¥ in Millions		Sep. 30, 2017	Mar. 31, 2017
Investments Classified by Contractual Maturity Date [Line Items]
Due in one year or less, amortized cost		¥ 6,400,429
Due after one year through five years, amortized cost		6,046,362
Due after five years through ten years,amortized cost		2,142,911
Due after ten years, amortized cost		1,226,561
Total		15,816,263
Due in one year or less, amortized cost		860,031
Due after one year through five years, amortized cost		1,120,025
Due after five years through ten years, amortized cost		479,882
Due after ten years, amortized cost		667,548
Amortized cost, held-to-maturity securities		3,127,486	¥ 3,817,360
Due in one year or less, fair value		6,398,245
Due after one year through five years, fair value		6,048,817
Due after five years through ten years, fair value		2,133,136
Due after ten years, fair value		1,278,834
Total		15,859,032
Due in one year or less, fair value		861,783
Due after one year through five years, fair value		1,125,592
Due after five years through ten years, fair value		500,674
Due after ten years, fair value		659,747
Total		3,147,796	3,846,718
Debt securities | Japanese government bonds
Investments Classified by Contractual Maturity Date [Line Items]
Due in one year or less, amortized cost		4,076,063
Due after one year through five years, amortized cost		4,201,851
Due after five years through ten years,amortized cost		1,394,917
Total		9,672,831
Due in one year or less, amortized cost		860,031
Due after one year through five years, amortized cost		1,120,025
Due after five years through ten years, amortized cost		479,882
Amortized cost, held-to-maturity securities		2,459,938	3,059,976
Due in one year or less, fair value		4,073,609
Due after one year through five years, fair value		4,200,457
Due after five years through ten years, fair value		1,384,158
Total		9,658,224
Due in one year or less, fair value		861,783
Due after one year through five years, fair value		1,125,592
Due after five years through ten years, fair value		500,674
Total		2,488,049	3,097,144
Debt securities | Agency mortgage-backed securities
Investments Classified by Contractual Maturity Date [Line Items]
Due after ten years, amortized cost		880,882
Total		880,882
Due after ten years, amortized cost		667,548
Amortized cost, held-to-maturity securities	[1]	667,548	757,384
Due after ten years, fair value		890,550
Total		890,550
Due after ten years, fair value		659,747
Total	[1]	659,747	¥ 749,574
Debt securities | Japanese local government bonds
Investments Classified by Contractual Maturity Date [Line Items]
Due in one year or less, amortized cost		30,530
Due after one year through five years, amortized cost		115,552
Due after five years through ten years,amortized cost		100,844
Due after ten years, amortized cost		4,097
Total		251,023
Due in one year or less, fair value		30,587
Due after one year through five years, fair value		116,166
Due after five years through ten years, fair value		102,671
Due after ten years, fair value		4,142
Total		253,566
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		716,047
Due after five years through ten years,amortized cost		137,650
Total		853,697
Due in one year or less, fair value		715,889
Due after five years through ten years, fair value		133,865
Total		849,754
Debt securities | Other foreign government bonds
Investments Classified by Contractual Maturity Date [Line Items]
Due in one year or less, amortized cost		706,741
Due after one year through five years, amortized cost		255,529
Due after five years through ten years,amortized cost		9,663
Total		971,933
Due in one year or less, fair value		706,840
Due after one year through five years, fair value		256,228
Due after five years through ten years, fair value		9,753
Total		972,821
Debt securities | Residential mortgage-backed securities
Investments Classified by Contractual Maturity Date [Line Items]
Due after ten years, amortized cost		135,814
Total		135,814
Due after ten years, fair value		136,797
Total		136,797
Debt securities | Commercial mortgage-backed securities
Investments Classified by Contractual Maturity Date [Line Items]
Due in one year or less, amortized cost		7,500
Due after one year through five years, amortized cost		159,599
Due after five years through ten years,amortized cost		80,278
Due after ten years, amortized cost		9,400
Total		256,777
Due in one year or less, fair value		7,504
Due after one year through five years, fair value		159,771
Due after five years through ten years, fair value		80,935
Due after ten years, fair value		9,176
Total		257,386
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		395,022
Due after one year through five years, amortized cost		963,809
Due after five years through ten years,amortized cost		351,649
Due after ten years, amortized cost		193,443
Total		1,903,923
Due in one year or less, fair value		395,270
Due after one year through five years, fair value		965,654
Due after five years through ten years, fair value		353,485
Due after ten years, fair value		235,257
Total		1,949,666
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		468,526
Due after one year through five years, amortized cost		350,022
Due after five years through ten years,amortized cost		67,910
Due after ten years, amortized cost		2,925
Total		889,383
Due in one year or less, fair value		468,546
Due after one year through five years, fair value		350,541
Due after five years through ten years, fair value		68,269
Due after ten years, fair value		2,912
Total		¥ 890,268
[1]	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, 2017	Sep. 30, 2016	Mar. 31, 2017
Gain (Loss) on Investments [Line Items]
Equity method Investments, carrying value	¥ 255,370		¥ 249,679
Held-to-maturity Securities
Gain (Loss) on Investments [Line Items]
Impairment loss on securities	¥ 0	¥ 0
Orient Corporation
Gain (Loss) on Investments [Line Items]
Percentage of proportionate share to the total outstanding common stock	49.00%
Equity securities (marketable)
Gain (Loss) on Investments [Line Items]
Equity method Investments, carrying value	¥ 140,613		132,817
Equity method Investments, aggregated market values	¥ 261,756		¥ 273,249

Investments (Other-Than-Tempora

Investments (Other-Than-Temporary Impairment Losses on Available-for-Sale Securities) (Detail) - JPY (¥) ¥ in Millions	6 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Gain (Loss) on Investments [Line Items]
Other-than-temporary impairment on available-for-sale securities	¥ 3,521	¥ 10,072
Debt securities
Gain (Loss) on Investments [Line Items]
Other-than-temporary impairment on available-for-sale securities	1,000	56
Equity securities
Gain (Loss) on Investments [Line Items]
Other-than-temporary impairment on available-for-sale securities	¥ 2,521	¥ 10,016

Investments (Gross Unrealized L

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, 2017	Mar. 31, 2017
Gain (Loss) on Investments [Line Items]
Less than 12 months, Fair value, available-for-sale securities		¥ 9,411,797	¥ 7,895,322
Less than 12 months Gross unrealized losses, available-for-sale securities		18,039	28,561
12 months or more Fair value, available-for-sale securities		1,955,265	433,597
12 months or more Gross unrealized losses, available-for-sale securities		17,520	4,697
Total Fair value, available-for-sale securities		11,367,062	8,328,919
Total Gross unrealized losses, available-for-sale securities		35,559	33,258
Less than 12 months, Fair value, held-to-maturity securities		406,351	460,882
Less than 12 months Gross unrealized losses, held-to-maturity securities		3,725	3,518
12 months or more Fair value, held-to-maturity securities		224,851	259,466
12 months or more Gross unrealized losses, held-to-maturity securities		4,127	4,413
Total Fair value, held-to-maturity securities		631,202	720,348
Total Gross unrealized losses, held-to-maturity securities		7,852	7,931
Debt securities | Agency mortgage-backed securities
Gain (Loss) on Investments [Line Items]
Less than 12 months, Fair value, available-for-sale securities	[1]	227,245	195,887
Less than 12 months Gross unrealized losses, available-for-sale securities	[1]	2,239	3,705
12 months or more Fair value, available-for-sale securities	[1]	77,620	42,501
12 months or more Gross unrealized losses, available-for-sale securities	[1]	2,074	1,736
Total Fair value, available-for-sale securities	[1]	304,865	238,388
Total Gross unrealized losses, available-for-sale securities	[1],[2]	4,313	5,441
Less than 12 months, Fair value, held-to-maturity securities	[3]	406,351	460,882
Less than 12 months Gross unrealized losses, held-to-maturity securities	[3]	3,725	3,518
12 months or more Fair value, held-to-maturity securities	[3]	224,851	259,466
12 months or more Gross unrealized losses, held-to-maturity securities	[3]	4,127	4,413
Total Fair value, held-to-maturity securities	[3]	631,202	720,348
Total Gross unrealized losses, held-to-maturity securities	[3]	7,852	7,931
Debt securities | Japanese government bonds
Gain (Loss) on Investments [Line Items]
Less than 12 months, Fair value, available-for-sale securities		7,198,653	5,574,649
Less than 12 months Gross unrealized losses, available-for-sale securities		9,958	15,796
12 months or more Fair value, available-for-sale securities		1,420,926	95,612
12 months or more Gross unrealized losses, available-for-sale securities		10,377	612
Total Fair value, available-for-sale securities		8,619,579	5,670,261
Total Gross unrealized losses, available-for-sale securities		20,335	16,408
Debt securities | Japanese local government bonds
Gain (Loss) on Investments [Line Items]
Less than 12 months, Fair value, available-for-sale securities		89,207	58,700
Less than 12 months Gross unrealized losses, available-for-sale securities		374	233
12 months or more Fair value, available-for-sale securities		7,802
12 months or more Gross unrealized losses, available-for-sale securities		90
Total Fair value, available-for-sale securities		97,009	58,700
Total Gross unrealized losses, available-for-sale securities		464	233
Debt securities | U.S. Treasury bonds and federal agency securities
Gain (Loss) on Investments [Line Items]
Less than 12 months, Fair value, available-for-sale securities		470,397	1,013,962
Less than 12 months Gross unrealized losses, available-for-sale securities		785	4,578
12 months or more Fair value, available-for-sale securities		79,294
12 months or more Gross unrealized losses, available-for-sale securities		3,311
Total Fair value, available-for-sale securities		549,691	1,013,962
Total Gross unrealized losses, available-for-sale securities		4,096	4,578
Debt securities | Other foreign government bonds
Gain (Loss) on Investments [Line Items]
Less than 12 months, Fair value, available-for-sale securities		551,664	334,300
Less than 12 months Gross unrealized losses, available-for-sale securities		785	230
12 months or more Fair value, available-for-sale securities		72,166	8,327
12 months or more Gross unrealized losses, available-for-sale securities		35	6
Total Fair value, available-for-sale securities		623,830	342,627
Total Gross unrealized losses, available-for-sale securities		820	236
Debt securities | Residential mortgage-backed securities
Gain (Loss) on Investments [Line Items]
Less than 12 months, Fair value, available-for-sale securities		18,093	5,873
Less than 12 months Gross unrealized losses, available-for-sale securities		43	3
12 months or more Fair value, available-for-sale securities		25,344	28,994
12 months or more Gross unrealized losses, available-for-sale securities		469	555
Total Fair value, available-for-sale securities		43,437	34,867
Total Gross unrealized losses, available-for-sale securities		512	558
Debt securities | Commercial mortgage-backed securities
Gain (Loss) on Investments [Line Items]
Less than 12 months, Fair value, available-for-sale securities		41,379	8,314
Less than 12 months Gross unrealized losses, available-for-sale securities		417	218
12 months or more Fair value, available-for-sale securities		12,292	17,634
12 months or more Gross unrealized losses, available-for-sale securities		37	64
Total Fair value, available-for-sale securities		53,671	25,948
Total Gross unrealized losses, available-for-sale securities		454	282
Debt securities | Japanese corporate bonds and other debt securities
Gain (Loss) on Investments [Line Items]
Less than 12 months, Fair value, available-for-sale securities		572,056	470,602
Less than 12 months Gross unrealized losses, available-for-sale securities		1,174	2,062
12 months or more Fair value, available-for-sale securities		206,284	158,713
12 months or more Gross unrealized losses, available-for-sale securities		376	224
Total Fair value, available-for-sale securities		778,340	629,315
Total Gross unrealized losses, available-for-sale securities	[4]	1,550	2,286
Debt securities | Foreign corporate bonds and other debt securities
Gain (Loss) on Investments [Line Items]
Less than 12 months, Fair value, available-for-sale securities		228,662	202,347
Less than 12 months Gross unrealized losses, available-for-sale securities		1,233	1,353
12 months or more Fair value, available-for-sale securities		31,828	77,699
12 months or more Gross unrealized losses, available-for-sale securities		319	290
Total Fair value, available-for-sale securities		260,490	280,046
Total Gross unrealized losses, available-for-sale securities	[5]	1,552	1,643
Equity securities (marketable)
Gain (Loss) on Investments [Line Items]
Less than 12 months, Fair value, available-for-sale securities		14,441	30,688
Less than 12 months Gross unrealized losses, available-for-sale securities		1,031	383
12 months or more Fair value, available-for-sale securities		21,709	4,117
12 months or more Gross unrealized losses, available-for-sale securities		432	1,210
Total Fair value, available-for-sale securities		36,150	34,805
Total Gross unrealized losses, available-for-sale securities		¥ 1,463	¥ 1,593
[1]	Agency mortgage-backed securities presented in this line consist of Japanese and Foreign agency mortgage-backed securities, of which the fair values were ¥104,270 million and ¥134,118 million, respectively, at March 31, 2017, and ¥144,319 million and ¥160,546 million, respectively, at September 30, 2017. 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.
[2]	Agency mortgage-backed securities presented in this line consist of Japanese and Foreign agency mortgage-backed securities, of which the fair values were ¥708,557 million and ¥134,240 million, respectively, at March 31, 2017, and ¥729,895 million and ¥160,655 million, respectively, at September 30, 2017. 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 certificates of deposit ("CDs"), of which the total fair values were ¥155,138 million at March 31, 2017, and ¥146,136 million at September 30, 2017.
[5]	Other debt securities presented in this line primarily consist of CDs and asset-backed securities ("ABS"), of which the total fair values were ¥258,059 million at March 31, 2017, and ¥290,380 million at September 30, 2017.

Investments (Gross Unrealized60

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, 2017	Mar. 31, 2017
Gain (Loss) on Investments [Line Items]
Fair value, available-for-sale securities		¥ 11,367,062	¥ 8,328,919
Agency mortgage-backed securities | Debt securities
Gain (Loss) on Investments [Line Items]
Fair value, available-for-sale securities	[1]	304,865	238,388
Foreign agency mortgage-backed securities | Agency mortgage-backed securities | Debt securities
Gain (Loss) on Investments [Line Items]
Fair value, available-for-sale securities		160,546	134,118
Japanese agency mortgage-backed securities | Agency mortgage-backed securities | Debt securities
Gain (Loss) on Investments [Line Items]
Fair value, available-for-sale securities		¥ 144,319	¥ 104,270
[1]	Agency mortgage-backed securities presented in this line consist of Japanese and Foreign agency mortgage-backed securities, of which the fair values were ¥104,270 million and ¥134,118 million, respectively, at March 31, 2017, and ¥144,319 million and ¥160,546 million, respectively, at September 30, 2017. 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 (Realized Gains and

Investments (Realized Gains and Losses on Sales of Available-for-Sale Securities) (Detail) - JPY (¥) ¥ in Millions	6 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Schedule of Available-for-sale Securities [Line Items]
Gross realized gains	¥ 127,360	¥ 144,796
Gross realized losses	(10,020)	(9,615)
Net realized gains (losses) on sales of available-for-sale securities	¥ 117,340	¥ 135,181

Investments (Summary of Composi

Investments (Summary of Composition of Other Investments) (Detail) - JPY (¥) ¥ in Millions	Sep. 30, 2017	Mar. 31, 2017
Schedule of Cost-method Investments [Line Items]
Equity method investments	¥ 255,370	¥ 249,679
Investments held by consolidated investment companies	38,779	37,462
Other equity interests	242,923	307,928
Total	¥ 537,072	¥ 595,069

Loans (Loans Outstanding by Dom

Loans (Loans Outstanding by Domicile and Industry of Borrower) (Detail) - JPY (¥) ¥ in Millions		Sep. 30, 2017	Mar. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[1]	¥ 84,028,246	¥ 82,439,581
Less: Unearned income and deferred loan fees-net		144,787	155,675
Loans outstanding		83,883,459	82,283,906
Domestic
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		59,088,273	57,656,540
Domestic | Manufacturing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		8,526,643	8,740,281
Domestic | Construction and real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		7,709,245	7,654,016
Domestic | Services
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		4,923,838	4,759,225
Domestic | Wholesale and retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		5,123,176	5,142,003
Domestic | Transportation and communications
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		3,413,710	3,490,415
Domestic | Banks and other financial institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		4,247,285	4,006,401
Domestic | Government and public institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		9,981,557	8,532,246
Domestic | Other industries
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[2]	4,502,531	4,427,349
Domestic | Mortgage loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		9,702,129	9,964,633
Domestic | Other individual loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		958,159	939,971
Foreign
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		24,939,973	24,783,041
Foreign | Banks and other financial institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		6,897,692	6,759,921
Foreign | Government and public institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		1,088,753	959,948
Foreign | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		16,915,590	16,872,448
Foreign | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[2]	¥ 37,938	¥ 190,724
[1]	Amounts represent loan balances before deducting unearned income and deferred loan fees.
[2]	Other industries of Domestic and Other of Foreign include trade receivables and lease receivables of consolidated VIEs.

Loans - Additional Information

Loans - Additional Information (Detail) - JPY (¥) ¥ in Millions	6 Months Ended	12 Months Ended
	Sep. 30, 2017	Mar. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net losses on sales of loans	¥ 3,739	¥ 919
Net losses on sales of loans, amount attributable to unrealized losses related to recording loans held for sale at the lower of cost or fair value	3,707	310
Loans held for sale	20,546	26,689
Impaired Financing Receivables with No Related Allowance
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired loans partially charged off	¥ 19,275	¥ 26,513
Minimum | Impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of days past due	90 days

Loans (Credit Quality Informati

Loans (Credit Quality Information of Loans Based on MHFG Group's Internal Rating System) (Detail) - JPY (¥) ¥ in Millions		Sep. 30, 2017	Mar. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[1]	¥ 84,028,246	¥ 82,439,581
Domestic
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		59,088,273	57,656,540
Domestic | Manufacturing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		8,526,643	8,740,281
Domestic | Construction and real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		7,709,245	7,654,016
Domestic | Services
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		4,923,838	4,759,225
Domestic | Wholesale and retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		5,123,176	5,142,003
Domestic | Transportation and communications
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		3,413,710	3,490,415
Domestic | Banks and other financial institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		4,247,285	4,006,401
Domestic | Government and public institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		9,981,557	8,532,246
Domestic | Other industries
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[2]	4,502,531	4,427,349
Domestic | Individuals
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		10,660,288	10,904,604
Foreign
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		24,939,973	24,783,041
Foreign | Banks and other financial institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		6,897,692	6,759,921
Foreign | Government and public institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		1,088,753	959,948
Foreign | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		16,915,590	16,872,448
Foreign | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[2]	37,938	190,724
Financing Receivables Not Impaired | Normal obligors | A-B
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		42,451,563	41,703,710
Financing Receivables Not Impaired | Normal obligors | C-D
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		16,606,333	17,436,758
Financing Receivables Not Impaired | Normal obligors | Retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[3]	11,166,995	11,445,049
Financing Receivables Not Impaired | Normal obligors | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[4]	11,742,502	9,413,741
Financing Receivables Not Impaired | Normal obligors | Domestic | A-B
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		26,276,746	26,023,413
Financing Receivables Not Impaired | Normal obligors | Domestic | A-B | Manufacturing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		5,302,937	5,313,232
Financing Receivables Not Impaired | Normal obligors | Domestic | A-B | Construction and real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		4,341,519	4,199,022
Financing Receivables Not Impaired | Normal obligors | Domestic | A-B | Services
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		2,802,307	2,699,487
Financing Receivables Not Impaired | Normal obligors | Domestic | A-B | Wholesale and retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		2,241,712	2,244,214
Financing Receivables Not Impaired | Normal obligors | Domestic | A-B | Transportation and communications
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		2,511,302	2,584,367
Financing Receivables Not Impaired | Normal obligors | Domestic | A-B | Banks and other financial institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		3,462,891	3,050,605
Financing Receivables Not Impaired | Normal obligors | Domestic | A-B | Government and public institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		3,237,595	4,059,349
Financing Receivables Not Impaired | Normal obligors | Domestic | A-B | Other industries
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[2]	2,376,483	1,873,137
Financing Receivables Not Impaired | Normal obligors | Domestic | C-D
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		11,182,154	11,808,379
Financing Receivables Not Impaired | Normal obligors | Domestic | C-D | Manufacturing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		2,718,865	2,599,760
Financing Receivables Not Impaired | Normal obligors | Domestic | C-D | Construction and real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		2,583,327	2,641,436
Financing Receivables Not Impaired | Normal obligors | Domestic | C-D | Services
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		1,647,922	1,687,515
Financing Receivables Not Impaired | Normal obligors | Domestic | C-D | Wholesale and retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		2,395,149	2,369,842
Financing Receivables Not Impaired | Normal obligors | Domestic | C-D | Transportation and communications
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		753,838	739,781
Financing Receivables Not Impaired | Normal obligors | Domestic | C-D | Banks and other financial institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		592,365	887,527
Financing Receivables Not Impaired | Normal obligors | Domestic | C-D | Government and public institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		1,600	1,600
Financing Receivables Not Impaired | Normal obligors | Domestic | C-D | Other industries
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[2]	188,887	591,109
Financing Receivables Not Impaired | Normal obligors | Domestic | C-D | Individuals
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		300,201	289,809
Financing Receivables Not Impaired | Normal obligors | Domestic | Retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[3]	11,157,745	11,435,437
Financing Receivables Not Impaired | Normal obligors | Domestic | Retail | Manufacturing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[3]	85,978	90,825
Financing Receivables Not Impaired | Normal obligors | Domestic | Retail | Construction and real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[3]	533,436	558,321
Financing Receivables Not Impaired | Normal obligors | Domestic | Retail | Services
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[3]	181,122	185,577
Financing Receivables Not Impaired | Normal obligors | Domestic | Retail | Wholesale and retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[3]	190,225	200,003
Financing Receivables Not Impaired | Normal obligors | Domestic | Retail | Transportation and communications
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[3]	79,972	82,543
Financing Receivables Not Impaired | Normal obligors | Domestic | Retail | Banks and other financial institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[3]	1,774	1,894
Financing Receivables Not Impaired | Normal obligors | Domestic | Retail | Other industries
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[2],[3]	3,634	3,535
Financing Receivables Not Impaired | Normal obligors | Domestic | Retail | Individuals
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[3]	10,081,604	10,312,739
Financing Receivables Not Impaired | Normal obligors | Domestic | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[4]	9,087,429	6,604,632
Financing Receivables Not Impaired | Normal obligors | Domestic | Other | Manufacturing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[4]	46,881	67,734
Financing Receivables Not Impaired | Normal obligors | Domestic | Other | Construction and real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[4]	8,471	15,585
Financing Receivables Not Impaired | Normal obligors | Domestic | Other | Services
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[4]	125,114	910
Financing Receivables Not Impaired | Normal obligors | Domestic | Other | Wholesale and retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[4]	13,830	22,785
Financing Receivables Not Impaired | Normal obligors | Domestic | Other | Transportation and communications
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[4]	1,948	1,092
Financing Receivables Not Impaired | Normal obligors | Domestic | Other | Banks and other financial institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[4]	160,314	37,907
Financing Receivables Not Impaired | Normal obligors | Domestic | Other | Government and public institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[4]	6,742,362	4,471,297
Financing Receivables Not Impaired | Normal obligors | Domestic | Other | Other industries
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[2],[4]	1,918,680	1,906,756
Financing Receivables Not Impaired | Normal obligors | Domestic | Other | Individuals
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[4]	69,829	80,566
Financing Receivables Not Impaired | Normal obligors | Foreign | A-B
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		16,174,817	15,680,297
Financing Receivables Not Impaired | Normal obligors | Foreign | A-B | Banks and other financial institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		5,867,251	5,628,387
Financing Receivables Not Impaired | Normal obligors | Foreign | A-B | Government and public institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		865,441	741,478
Financing Receivables Not Impaired | Normal obligors | Foreign | A-B | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		9,442,125	9,310,432
Financing Receivables Not Impaired | Normal obligors | Foreign | C-D
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		5,424,179	5,628,379
Financing Receivables Not Impaired | Normal obligors | Foreign | C-D | Banks and other financial institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		563,445	592,380
Financing Receivables Not Impaired | Normal obligors | Foreign | C-D | Government and public institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		220,632	214,558
Financing Receivables Not Impaired | Normal obligors | Foreign | C-D | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		4,635,302	4,814,906
Financing Receivables Not Impaired | Normal obligors | Foreign | C-D | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[2]	4,800	6,535
Financing Receivables Not Impaired | Normal obligors | Foreign | Retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[3]	9,250	9,612
Financing Receivables Not Impaired | Normal obligors | Foreign | Retail | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[3]	206	173
Financing Receivables Not Impaired | Normal obligors | Foreign | Retail | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[2],[3]	9,044	9,439
Financing Receivables Not Impaired | Normal obligors | Foreign | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[4]	2,655,073	2,809,109
Financing Receivables Not Impaired | Normal obligors | Foreign | Other | Banks and other financial institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[4]	411,234	480,806
Financing Receivables Not Impaired | Normal obligors | Foreign | Other | Government and public institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[4]	861	1,082
Financing Receivables Not Impaired | Normal obligors | Foreign | Other | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[4]	2,221,178	2,153,757
Financing Receivables Not Impaired | Normal obligors | Foreign | Other | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[2],[4]	21,800	173,464
Financing Receivables Not Impaired | Watch obligors | Retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[3],[5]	174,619	183,247
Financing Receivables Not Impaired | Watch obligors | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[4],[5]	93,226	136,424
Financing Receivables Not Impaired | Watch obligors | E1 to E2 Rating
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[5]	1,120,535	1,139,768
Financing Receivables Not Impaired | Watch obligors | Domestic | Retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[3],[5]	174,612	183,239
Financing Receivables Not Impaired | Watch obligors | Domestic | Retail | Manufacturing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[3],[5]	10,880	11,589
Financing Receivables Not Impaired | Watch obligors | Domestic | Retail | Construction and real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[3],[5]	16,592	16,023
Financing Receivables Not Impaired | Watch obligors | Domestic | Retail | Services
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[3],[5]	21,722	23,189
Financing Receivables Not Impaired | Watch obligors | Domestic | Retail | Wholesale and retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[3],[5]	31,369	32,911
Financing Receivables Not Impaired | Watch obligors | Domestic | Retail | Transportation and communications
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[3],[5]	9,275	9,698
Financing Receivables Not Impaired | Watch obligors | Domestic | Retail | Banks and other financial institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[3],[5]	220	353
Financing Receivables Not Impaired | Watch obligors | Domestic | Retail | Other industries
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[2],[3],[5]	289	410
Financing Receivables Not Impaired | Watch obligors | Domestic | Retail | Individuals
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[3],[5]	84,265	89,066
Financing Receivables Not Impaired | Watch obligors | Domestic | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[4],[5]	11,110	44,949
Financing Receivables Not Impaired | Watch obligors | Domestic | Other | Manufacturing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[4],[5]	239	1,314
Financing Receivables Not Impaired | Watch obligors | Domestic | Other | Construction and real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[4],[5]		317
Financing Receivables Not Impaired | Watch obligors | Domestic | Other | Services
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[4],[5]		204
Financing Receivables Not Impaired | Watch obligors | Domestic | Other | Wholesale and retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[4],[5]	669	501
Financing Receivables Not Impaired | Watch obligors | Domestic | Other | Other industries
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[2],[4],[5]	8,927	41,179
Financing Receivables Not Impaired | Watch obligors | Domestic | Other | Individuals
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[4],[5]	1,275	1,434
Financing Receivables Not Impaired | Watch obligors | Domestic | E1 to E2 Rating
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[5]	680,526	766,220
Financing Receivables Not Impaired | Watch obligors | Domestic | E1 to E2 Rating | Manufacturing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[5]	225,293	276,771
Financing Receivables Not Impaired | Watch obligors | Domestic | E1 to E2 Rating | Construction and real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[5]	174,429	165,836
Financing Receivables Not Impaired | Watch obligors | Domestic | E1 to E2 Rating | Services
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[5]	89,500	95,973
Financing Receivables Not Impaired | Watch obligors | Domestic | E1 to E2 Rating | Wholesale and retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[5]	110,009	124,846
Financing Receivables Not Impaired | Watch obligors | Domestic | E1 to E2 Rating | Transportation and communications
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[5]	30,502	50,319
Financing Receivables Not Impaired | Watch obligors | Domestic | E1 to E2 Rating | Banks and other financial institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[5]	22,659	21,574
Financing Receivables Not Impaired | Watch obligors | Domestic | E1 to E2 Rating | Other industries
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[2],[5]	2,368	4,613
Financing Receivables Not Impaired | Watch obligors | Domestic | E1 to E2 Rating | Individuals
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[5]	25,766	26,288
Financing Receivables Not Impaired | Watch obligors | Foreign | Retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[3],[5]	7	8
Financing Receivables Not Impaired | Watch obligors | Foreign | Retail | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[2],[3],[5]	7	8
Financing Receivables Not Impaired | Watch obligors | Foreign | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[4],[5]	82,116	91,475
Financing Receivables Not Impaired | Watch obligors | Foreign | Other | Banks and other financial institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[4],[5]	927
Financing Receivables Not Impaired | Watch obligors | Foreign | Other | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[4],[5]	79,905	90,722
Financing Receivables Not Impaired | Watch obligors | Foreign | Other | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[2],[4],[5]	1,284	753
Financing Receivables Not Impaired | Watch obligors | Foreign | E1 to E2 Rating
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[5]	440,009	373,548
Financing Receivables Not Impaired | Watch obligors | Foreign | E1 to E2 Rating | Banks and other financial institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[5]	54,835	58,348
Financing Receivables Not Impaired | Watch obligors | Foreign | E1 to E2 Rating | Government and public institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[5]	1,800	2,801
Financing Receivables Not Impaired | Watch obligors | Foreign | E1 to E2 Rating | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[5]	383,128	312,275
Financing Receivables Not Impaired | Watch obligors | Foreign | E1 to E2 Rating | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[2],[5]	246	124
Financing Receivables Impaired | Impaired loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		672,473	980,884
Financing Receivables Impaired | Impaired loans | Domestic
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		517,951	790,271
Financing Receivables Impaired | Impaired loans | Domestic | Manufacturing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		135,570	379,056
Financing Receivables Impaired | Impaired loans | Domestic | Construction and real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		51,471	57,476
Financing Receivables Impaired | Impaired loans | Domestic | Services
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		56,151	66,370
Financing Receivables Impaired | Impaired loans | Domestic | Wholesale and retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		140,213	146,901
Financing Receivables Impaired | Impaired loans | Domestic | Transportation and communications
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		26,873	22,615
Financing Receivables Impaired | Impaired loans | Domestic | Banks and other financial institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		7,062	6,541
Financing Receivables Impaired | Impaired loans | Domestic | Other industries
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[2]	3,263	6,610
Financing Receivables Impaired | Impaired loans | Domestic | Individuals
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		97,348	104,702
Financing Receivables Impaired | Impaired loans | Foreign
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		154,522	190,613
Financing Receivables Impaired | Impaired loans | Foreign | Government and public institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		19	29
Financing Receivables Impaired | Impaired loans | Foreign | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding		153,746	190,183
Financing Receivables Impaired | Impaired loans | Foreign | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	[2]	¥ 757	¥ 401
[1]	Amounts represent loan balances before deducting unearned income and deferred loan fees.
[2]	Other industries of Domestic and Other of Foreign include trade receivables and lease receivables of consolidated VIEs.
[3]	Amounts represent small balance, homogeneous loans which are subject to pool allocations.
[4]	Non-impaired loans held by subsidiaries other than MHBK and MHTB constitute Other, since their portfolio segments are not identical to those of MHBK and MHTB.
[5]	Special attention obligors are watch obligors with debt in TDR or 90 days or more delinquent debt. Loans to such obligors are considered impaired.

Loans (Impaired Loans Informati

Loans (Impaired Loans Information) (Detail) - JPY (¥) ¥ in Millions		6 Months Ended	12 Months Ended
		Sep. 30, 2017	Mar. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment requiring an allowance for loan losses	[1]	¥ 550,868	¥ 851,130
Recorded investment not requiring an allowance for loan losses	[1],[2]	121,605	129,754
Total	[1]	672,473	980,884
Unpaid principal balance		726,173	1,038,292
Related allowance	[3]	179,712	302,573
Average recorded investment		826,678	976,295
Interest income recognized	[4]	4,719	11,418
Domestic
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment requiring an allowance for loan losses	[1]	423,435	690,567
Recorded investment not requiring an allowance for loan losses	[1],[2]	94,516	99,704
Total	[1]	517,951	790,271
Unpaid principal balance		553,650	829,163
Related allowance	[3]	131,092	241,471
Average recorded investment		654,111	807,103
Interest income recognized	[4]	3,650	9,378
Domestic | Manufacturing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment requiring an allowance for loan losses	[1]	130,184	372,241
Recorded investment not requiring an allowance for loan losses	[1],[2]	5,386	6,815
Total	[1]	135,570	379,056
Unpaid principal balance		140,010	383,812
Related allowance	[3]	48,786	148,777
Average recorded investment		257,313	375,895
Interest income recognized	[4]	914	2,859
Domestic | Construction and real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment requiring an allowance for loan losses	[1]	41,808	46,130
Recorded investment not requiring an allowance for loan losses	[1],[2]	9,663	11,346
Total	[1]	51,471	57,476
Unpaid principal balance		59,519	66,006
Related allowance	[3]	5,397	6,367
Average recorded investment		54,473	66,796
Interest income recognized	[4]	338	877
Domestic | Services
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment requiring an allowance for loan losses	[1]	46,498	58,366
Recorded investment not requiring an allowance for loan losses	[1],[2]	9,653	8,004
Total	[1]	56,151	66,370
Unpaid principal balance		63,777	72,261
Related allowance	[3]	12,280	20,122
Average recorded investment		61,260	66,050
Interest income recognized	[4]	432	1,173
Domestic | Wholesale and retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment requiring an allowance for loan losses	[1]	129,030	133,466
Recorded investment not requiring an allowance for loan losses	[1],[2]	11,183	13,435
Total	[1]	140,213	146,901
Unpaid principal balance		148,775	155,023
Related allowance	[3]	49,871	52,341
Average recorded investment		143,557	148,865
Interest income recognized	[4]	1,031	2,261
Domestic | Transportation and communications
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment requiring an allowance for loan losses	[1]	24,139	19,386
Recorded investment not requiring an allowance for loan losses	[1],[2]	2,734	3,229
Total	[1]	26,873	22,615
Unpaid principal balance		27,865	23,568
Related allowance	[3]	7,134	5,968
Average recorded investment		24,744	24,035
Interest income recognized	[4]	160	371
Domestic | Banks and other financial institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment requiring an allowance for loan losses	[1]	3,100	2,601
Recorded investment not requiring an allowance for loan losses	[1],[2]	3,962	3,940
Total	[1]	7,062	6,541
Unpaid principal balance		7,395	6,873
Related allowance	[3]	1,433	962
Average recorded investment		6,802	5,305
Interest income recognized	[4]	29	50
Domestic | Other industries
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment requiring an allowance for loan losses	[1]	2,184	6,484
Recorded investment not requiring an allowance for loan losses	[1],[2]	1,079	126
Total	[1]	3,263	6,610
Unpaid principal balance		3,393	6,740
Related allowance	[3]	1,534	1,999
Average recorded investment		4,937	6,053
Interest income recognized	[4]	17	91
Domestic | Individuals
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment requiring an allowance for loan losses	[1]	46,492	51,893
Recorded investment not requiring an allowance for loan losses	[1],[2]	50,856	52,809
Total	[1]	97,348	104,702
Unpaid principal balance		102,916	114,880
Related allowance	[3]	4,657	4,935
Average recorded investment		101,025	114,104
Interest income recognized	[4]	729	1,696
Foreign
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment requiring an allowance for loan losses	[1]	127,433	160,563
Recorded investment not requiring an allowance for loan losses	[1],[2]	27,089	30,050
Total	[1]	154,522	190,613
Unpaid principal balance		172,523	209,129
Related allowance	[3]	48,620	61,102
Average recorded investment		172,567	169,192
Interest income recognized	[4]	¥ 1,069	¥ 2,040
[1]	Amounts represent the outstanding balances of nonaccrual loans. The MHFG Group's policy for placing loans in nonaccrual status corresponds to the Group's definition of impaired loans.
[2]	These impaired loans do not require an allowance for loan losses because the MHFG Group has sufficient collateral to cover probable loan losses.
[3]	The allowance for loan losses on impaired loans includes the allowance for groups of small balance, homogeneous loans which were collectively evaluated for impairment, in addition to the allowance for those loans that were individually evaluated for impairment. The total carrying amount of the groups of small balance, homogeneous loans at March 31, 2017 and September 30, 2017 was ¥302,251 million and ¥266,915 million, respectively.
[4]	Amounts represent gross interest income on impaired loans which were included in Interest income on loans in the consolidated statements of income.

Loans (Impaired Loans Informa67

Loans (Impaired Loans Information) (Parenthetical) (Detail) - JPY (¥) ¥ in Millions		Sep. 30, 2017	Mar. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	[1]	¥ 672,473	¥ 980,884
Small balance homogeneous loans of which were collectively evaluated for impairment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment		¥ 266,915	¥ 302,251
[1]	Amounts represent the outstanding balances of nonaccrual loans. The MHFG Group's policy for placing loans in nonaccrual status corresponds to the Group's definition of impaired loans.

Loans (Troubled Debt Restructur

Loans (Troubled Debt Restructurings Entered into During Periods by Type of Concession Granted) (Detail) - JPY (¥) ¥ in Millions		6 Months Ended
		Sep. 30, 2017	Sep. 30, 2016
Financing Receivable, Modifications [Line Items]
Loan forgiveness or debt to equity swaps Recorded investment	[1]	¥ 0	¥ 0
Loan forgiveness or debt to equity swaps charge-off		0	0
Interest rate reduction and/or postponement of principal and/or interest		194,648	206,442
Domestic
Financing Receivable, Modifications [Line Items]
Loan forgiveness or debt to equity swaps Recorded investment	[1]	0	0
Loan forgiveness or debt to equity swaps charge-off		0	0
Interest rate reduction and/or postponement of principal and/or interest		181,345	195,593
Domestic | Manufacturing
Financing Receivable, Modifications [Line Items]
Loan forgiveness or debt to equity swaps Recorded investment	[1]	0	0
Loan forgiveness or debt to equity swaps charge-off		0	0
Interest rate reduction and/or postponement of principal and/or interest		55,611	54,476
Domestic | Construction and real estate
Financing Receivable, Modifications [Line Items]
Loan forgiveness or debt to equity swaps Recorded investment	[1]	0	0
Loan forgiveness or debt to equity swaps charge-off		0	0
Interest rate reduction and/or postponement of principal and/or interest		9,045	8,596
Domestic | Services
Financing Receivable, Modifications [Line Items]
Loan forgiveness or debt to equity swaps Recorded investment	[1]	0	0
Loan forgiveness or debt to equity swaps charge-off		0	0
Interest rate reduction and/or postponement of principal and/or interest		18,740	21,951
Domestic | Wholesale and retail
Financing Receivable, Modifications [Line Items]
Loan forgiveness or debt to equity swaps Recorded investment	[1]	0	0
Loan forgiveness or debt to equity swaps charge-off		0	0
Interest rate reduction and/or postponement of principal and/or interest		74,625	87,237
Domestic | Transportation and communications
Financing Receivable, Modifications [Line Items]
Loan forgiveness or debt to equity swaps Recorded investment	[1]	0	0
Loan forgiveness or debt to equity swaps charge-off		0	0
Interest rate reduction and/or postponement of principal and/or interest		12,244	8,656
Domestic | Banks and other financial institutions
Financing Receivable, Modifications [Line Items]
Loan forgiveness or debt to equity swaps Recorded investment	[1]	0	0
Loan forgiveness or debt to equity swaps charge-off		0	0
Interest rate reduction and/or postponement of principal and/or interest		3,461	3,198
Domestic | Other industries
Financing Receivable, Modifications [Line Items]
Loan forgiveness or debt to equity swaps Recorded investment	[1]		0
Loan forgiveness or debt to equity swaps charge-off			0
Interest rate reduction and/or postponement of principal and/or interest			2,274
Domestic | Individuals
Financing Receivable, Modifications [Line Items]
Loan forgiveness or debt to equity swaps Recorded investment	[1]	0	0
Loan forgiveness or debt to equity swaps charge-off		0	0
Interest rate reduction and/or postponement of principal and/or interest		7,619	9,205
Foreign
Financing Receivable, Modifications [Line Items]
Loan forgiveness or debt to equity swaps Recorded investment	[1]	0	0
Loan forgiveness or debt to equity swaps charge-off		0	0
Interest rate reduction and/or postponement of principal and/or interest		¥ 13,303	¥ 10,849
[1]	Amounts represent the book values of loans immediately after the restructurings.

Loans (Payment Defaults Occurre

Loans (Payment Defaults Occurred During Periods with Respect to Loans Modified as Troubled Debt Restructurings within Previous Twelve Months) (Detail) - JPY (¥) ¥ in Millions	6 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Financing Receivable, Modifications [Line Items]
Recorded investment	¥ 23,856	¥ 11,391
Other industries
Financing Receivable, Modifications [Line Items]
Recorded investment	130
Domestic
Financing Receivable, Modifications [Line Items]
Recorded investment	19,268	11,361
Domestic | Manufacturing
Financing Receivable, Modifications [Line Items]
Recorded investment	2,006	1,801
Domestic | Construction and real estate
Financing Receivable, Modifications [Line Items]
Recorded investment	70	1,621
Domestic | Services
Financing Receivable, Modifications [Line Items]
Recorded investment	2,561	1,188
Domestic | Wholesale and retail
Financing Receivable, Modifications [Line Items]
Recorded investment	13,396	4,614
Domestic | Transportation and communications
Financing Receivable, Modifications [Line Items]
Recorded investment	201	771
Domestic | Individuals
Financing Receivable, Modifications [Line Items]
Recorded investment	904	1,366
Foreign
Financing Receivable, Modifications [Line Items]
Recorded investment	¥ 4,588	¥ 30

Loans (Age Analysis of Past Due

Loans (Age Analysis of Past Due Loans) (Detail) - JPY (¥) ¥ in Millions		Sep. 30, 2017	Mar. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due		¥ 215,768	¥ 242,397
Current		83,812,478	82,197,184
Total	[1]	84,028,246	82,439,581
Domestic
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due		140,560	145,916
Current		58,947,713	57,510,624
Total		59,088,273	57,656,540
Domestic | Manufacturing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due		10,338	10,065
Current		8,516,305	8,730,216
Total		8,526,643	8,740,281
Domestic | Construction and real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due		29,815	36,288
Current		7,679,430	7,617,728
Total		7,709,245	7,654,016
Domestic | Services
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due		8,511	7,048
Current		4,915,327	4,752,177
Total		4,923,838	4,759,225
Domestic | Wholesale and retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due		6,642	9,749
Current		5,116,534	5,132,254
Total		5,123,176	5,142,003
Domestic | Transportation and communications
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due		7,663	2,565
Current		3,406,047	3,487,850
Total		3,413,710	3,490,415
Domestic | Banks and other financial institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current		4,247,285	4,006,401
Total		4,247,285	4,006,401
Domestic | Government and public institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current		9,981,557	8,532,246
Total		9,981,557	8,532,246
Domestic | Other industries
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due		65	69
Current		4,502,466	4,427,280
Total	[2]	4,502,531	4,427,349
Domestic | Individuals
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due		77,526	80,132
Current		10,582,762	10,824,472
Total		10,660,288	10,904,604
Foreign
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due		75,208	96,481
Current		24,864,765	24,686,560
Total		24,939,973	24,783,041
Foreign | Banks and other financial institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total		6,897,692	6,759,921
Foreign | Government and public institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total		1,088,753	959,948
30-59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due		39,179	40,928
30-59 Days Past Due | Domestic
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due		38,331	40,382
30-59 Days Past Due | Domestic | Manufacturing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due		1,504	1,938
30-59 Days Past Due | Domestic | Construction and real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due		1,006	2,818
30-59 Days Past Due | Domestic | Services
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due		2,076	917
30-59 Days Past Due | Domestic | Wholesale and retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due		1,842	1,330
30-59 Days Past Due | Domestic | Transportation and communications
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due		76	384
30-59 Days Past Due | Domestic | Other industries
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due		40
30-59 Days Past Due | Domestic | Individuals
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due		31,787	32,995
30-59 Days Past Due | Foreign
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due		848	546
60-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due		15,495	17,187
60-89 Days Past Due | Domestic
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due		15,033	16,971
60-89 Days Past Due | Domestic | Manufacturing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due		289	360
60-89 Days Past Due | Domestic | Construction and real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due		940	947
60-89 Days Past Due | Domestic | Services
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due		1,537	217
60-89 Days Past Due | Domestic | Wholesale and retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due		997	2,834
60-89 Days Past Due | Domestic | Transportation and communications
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due		85	322
60-89 Days Past Due | Domestic | Individuals
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due		11,185	12,291
60-89 Days Past Due | Foreign
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due		462	216
90 Days or More Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due		161,094	184,282
90 Days or More Past Due | Domestic
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due		87,196	88,563
90 Days or More Past Due | Domestic | Manufacturing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due		8,545	7,767
90 Days or More Past Due | Domestic | Construction and real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due		27,869	32,523
90 Days or More Past Due | Domestic | Services
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due		4,898	5,914
90 Days or More Past Due | Domestic | Wholesale and retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due		3,803	5,585
90 Days or More Past Due | Domestic | Transportation and communications
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due		7,502	1,859
90 Days or More Past Due | Domestic | Other industries
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due		25	69
90 Days or More Past Due | Domestic | Individuals
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due		34,554	34,846
90 Days or More Past Due | Foreign
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total past due		¥ 73,898	¥ 95,719
[1]	Amounts represent loan balances before deducting unearned income and deferred loan fees.
[2]	Other industries of Domestic and Other of Foreign include trade receivables and lease receivables of consolidated VIEs.

Allowance for Loan Losses - Add

Allowance for Loan Losses - Additional Information (Detail)	6 Months Ended
	Sep. 30, 2016
Minimum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Period in which obligors generally determined to be substantially bankrupt, past due (in months)	6 months

Allowance for Loan Losses (Chan

Allowance for Loan Losses (Changes in Allowance for Loan Losses, Allowance for Loan Losses and Loans Outstanding Disaggregated on Basis of Impairment Method, by Portfolio Segment) (Detail) - JPY (¥) ¥ in Millions		6 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Mar. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at beginning of period		¥ 479,673	¥ 451,247
Provision (credit) for loan losses		(117,962)	569
Charge-offs		(21,218)	(15,160)
Recoveries		8,009	15,741
Net charge-offs		(13,209)	581
Others	[1]	1,967	(15,217)
Balance at end of fiscal year		350,469	437,180
Allowance for loan losses of which individually evaluated for impairment		180,518		¥ 288,942
Allowance for loan losses of which collectively evaluated for impairment		169,951		190,731
Loans	[2]	84,028,246		82,439,581
Loans of which individually evaluated for impairment	[2]	757,133		861,144
Loans of which collectively evaluated for impairment	[2]	83,271,113		81,578,437
Corporate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at beginning of period		407,327	367,739
Provision (credit) for loan losses		(109,379)	9,123
Charge-offs		(17,366)	(10,332)
Recoveries		6,447	8,877
Net charge-offs		(10,919)	(1,455)
Others	[1]	2,552	(10,404)
Balance at end of fiscal year		289,581	365,003
Allowance for loan losses of which individually evaluated for impairment		170,509		272,714
Allowance for loan losses of which collectively evaluated for impairment		119,072		134,613
Loans	[2]	60,727,073		61,120,654
Loans of which individually evaluated for impairment	[2]	673,081		772,647
Loans of which collectively evaluated for impairment	[2]	60,053,992		60,348,007
Retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at beginning of period		36,923	44,221
Provision (credit) for loan losses		(6,469)	(7,983)
Charge-offs		(745)	(1,016)
Recoveries		315	4,725
Net charge-offs		(430)	3,709
Balance at end of fiscal year		30,024	39,947
Allowance for loan losses of which individually evaluated for impairment		2,761		2,922
Allowance for loan losses of which collectively evaluated for impairment		27,263		34,001
Loans	[2]	11,432,376		11,722,726
Loans of which individually evaluated for impairment	[2]	22,734		23,422
Loans of which collectively evaluated for impairment	[2]	11,409,642		11,699,304
Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at beginning of period		35,423	39,287
Provision (credit) for loan losses		(2,114)	(571)
Charge-offs		(3,107)	(3,812)
Recoveries		1,247	2,139
Net charge-offs		(1,860)	(1,673)
Others	[1]	(585)	(4,813)
Balance at end of fiscal year		30,864	¥ 32,230
Allowance for loan losses of which individually evaluated for impairment		7,248		13,306
Allowance for loan losses of which collectively evaluated for impairment		23,616		22,117
Loans	[2]	11,868,797		9,596,201
Loans of which individually evaluated for impairment	[2]	61,318		65,075
Loans of which collectively evaluated for impairment	[2]	¥ 11,807,479		¥ 9,531,126
[1]	Others includes primarily foreign exchange translation.
[2]	Amounts represent loan balances before deducting unearned income and deferred loan fees.

Other Assets and Liabilities (D

Other Assets and Liabilities (Details of Other Assets and Liabilities) (Detail) - JPY (¥) ¥ in Millions	Sep. 30, 2017	Mar. 31, 2017
Other assets:
Accounts receivable from brokers, dealers and customers for securities transactions	¥ 2,000,669	¥ 1,564,295
Collateral provided for derivative transactions	1,110,240	973,404
Prepaid pension cost	707,464	682,592
Margins provided for futures contracts	363,325	276,398
Miscellaneous receivables	294,262	324,135
Security deposits	127,302	122,858
Loans held for sale	20,546	26,689
Other	1,484,483	1,021,958
Total	6,108,291	4,992,329
Other liabilities:
Accounts payable to brokers, dealers and customers for securities transactions	2,710,819	1,400,141
Guaranteed trust principal	714,801	683,324
Collateral accepted for derivative transactions	568,881	671,691
Miscellaneous payables	456,138	481,809
Margins accepted for futures contracts	363,221	307,066
Unearned income	130,480	134,666
Factoring amounts owed to customers	22,810	53,488
Other	1,088,413	1,294,340
Total	¥ 6,055,563	¥ 5,026,525

Preferred and Common Stock (Com

Preferred and Common Stock (Composition of Preferred Stock) (Detail) - shares		Sep. 30, 2017	Mar. 31, 2017
Class of Stock [Line Items]
Number of shares Authorized		3,300,000,000	4,214,752,000
Number of shares Issued		0	0
Class XI preferred stock
Class of Stock [Line Items]
Number of shares Authorized			914,752,000
Number of shares Issued		0	0
First series class XIV preferred stock
Class of Stock [Line Items]
Number of shares Authorized	[1]	900,000,000	900,000,000
Number of shares Issued	[1]	0	0
Second series class XIV preferred stock
Class of Stock [Line Items]
Number of shares Authorized	[1]	900,000,000	900,000,000
Number of shares Issued	[1]	0	0
Third series class XIV preferred stock
Class of Stock [Line Items]
Number of shares Authorized	[1]	900,000,000	900,000,000
Number of shares Issued	[1]	0	0
Fourth series class XIV preferred stock
Class of Stock [Line Items]
Number of shares Authorized	[1]	900,000,000	900,000,000
Number of shares Issued	[1]	0	0
First series class XV preferred stock
Class of Stock [Line Items]
Number of shares Authorized	[2]	900,000,000	900,000,000
Number of shares Issued	[2]	0	0
Second series class XV preferred stock
Class of Stock [Line Items]
Number of shares Authorized	[2]	900,000,000	900,000,000
Number of shares Issued	[2]	0	0
Third series class XV preferred stock
Class of Stock [Line Items]
Number of shares Authorized	[2]	900,000,000	900,000,000
Number of shares Issued	[2]	0	0
Fourth series class XV preferred stock
Class of Stock [Line Items]
Number of shares Authorized	[2]	900,000,000	900,000,000
Number of shares Issued	[2]	0	0
First series class XVI preferred stock
Class of Stock [Line Items]
Number of shares Authorized	[3]	1,500,000,000	1,500,000,000
Number of shares Issued	[3]	0	0
Second series class XVI preferred stock
Class of Stock [Line Items]
Number of shares Authorized	[3]	1,500,000,000	1,500,000,000
Number of shares Issued	[3]	0	0
Third series class XVI preferred stock
Class of Stock [Line Items]
Number of shares Authorized	[3]	1,500,000,000	1,500,000,000
Number of shares Issued	[3]	0	0
Fourth series class XVI preferred stock
Class of Stock [Line Items]
Number of shares Authorized	[3]	1,500,000,000	1,500,000,000
Number of shares Issued	[3]	0	0
[1]	The total number of authorized shares from first to fourth series class XIV preferred stock shall not exceed 900,000,000.
[2]	The total number of authorized shares from first to fourth series class XV preferred stock shall not exceed 900,000,000.
[3]	The total number of authorized shares from first to fourth series class XVI preferred stock shall not exceed 1,500,000,000.

Preferred and Common Stock (C75

Preferred and Common Stock (Composition of Preferred Stock) (Parenthetical) (Detail) - shares	Sep. 30, 2017	Mar. 31, 2017
Class of Stock [Line Items]
Number of shares Authorized	3,300,000,000	4,214,752,000
First to fourth series class XIV Preferred Stock | Maximum
Class of Stock [Line Items]
Number of shares Authorized	900,000,000
First to fourth series class XV Preferred Stock | Maximum
Class of Stock [Line Items]
Number of shares Authorized	900,000,000
First to fourth series class XVI Preferred Stock | Maximum
Class of Stock [Line Items]
Number of shares Authorized	1,500,000,000

Preferred and Common Stock - Ad

Preferred and Common Stock - Additional Information (Detail) - shares	6 Months Ended
	Sep. 30, 2017	Mar. 31, 2017
Class of Stock [Line Items]
Common stock, issued	25,389,644,945	25,386,307,945
Increase in common stock shares	3,337,000

Dividends (Dividends on Preferr

Dividends (Dividends on Preferred Stock and Common Stock) (Detail) - JPY (¥) ¥ / shares in Units, ¥ in Millions	6 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Japan Gaap Dividends Payable [Line Items]
Cash dividends In aggregate		¥ 94,828
Eleventh series class XI preferred stock
Japan Gaap Dividends Payable [Line Items]
Cash dividends Per share		¥ 10
Cash dividends In aggregate		¥ 989
Common stock
Japan Gaap Dividends Payable [Line Items]
Cash dividends Per share	¥ 3.75	¥ 3.75
Cash dividends In aggregate	¥ 95,174	¥ 93,839

Accumulated Other Comprehensi78

Accumulated Other Comprehensive Income (Changes in Each Component of Accumulated Other Comprehensive Income, Net of Tax) (Detail) - JPY (¥) ¥ in Millions	6 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	¥ 8,772,057
Less: reclassification adjustments for losses (gains) included in net income	(78,629)
Change during period	165,077	¥ (196,229)
Balance at end of period	9,200,761	8,264,977
Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	1,521,163	1,469,308
Cumulative effect of change in accounting principles (Note 17)		330
Balance at beginning of period, adjusted	1,521,163	1,469,638
Change during period	164,684	(195,339)
Balance at end of period	1,685,847	1,274,299
Net unrealized gains (losses) on available-for-sale securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	1,461,302	1,409,459
Cumulative effect of change in accounting principles (Note 17)		(85)
Balance at beginning of period, adjusted	1,461,302	1,409,374
Foreign currency translation adjustments during period	247,493	(49,362)
Less: reclassification adjustments for losses (gains) included in net income	(78,659)	(86,761)
Change during period	168,834	(136,123)
Balance at end of period	1,630,136	1,273,251
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(5,535)	6,310
Cumulative effect of change in accounting principles (Note 17)		415
Balance at beginning of period, adjusted	(5,535)	6,725
Foreign currency translation adjustments during period	(4,322)	(59,893)
Change during period	(4,322)	(59,893)
Balance at end of period	(9,857)	(53,168)
Pension liability adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	65,396	53,539
Foreign currency translation adjustments during period	32	533
Less: reclassification adjustments for losses (gains) included in net income	140	144
Change during period	172	677
Balance at end of period	¥ 65,568	¥ 54,216

Accumulated Other Comprehensi79

Accumulated Other Comprehensive Income (Amounts Reclassified Out of Accumulated Other Comprehensive Income into Net Income) (Detail) ¥ in Millions	6 Months Ended
	Sep. 30, 2017JPY (¥)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Before tax	¥ 113,586	[1]
Tax effect	(34,957)	[2]
Net of tax before allocation to noncontrolling interests	78,629
Net of tax attributable to noncontrolling interests	(110)	[2]
Net of tax attributable to MHFG shareholders	78,519
Accumulated Net Unrealized Investment Gain (Loss) | Gain (Loss) on Investments [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Before tax	113,819	[1]
Tax effect	(35,053)	[2]
Net of tax before allocation to noncontrolling interests	78,766
Net of tax attributable to noncontrolling interests	(107)	[2]
Net of tax attributable to MHFG shareholders	78,659
Accumulated Defined Benefit Plans Adjustment | Salaries and employee benefits
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Before tax	(233)	[1]
Tax effect	96	[2]
Net of tax before allocation to noncontrolling interests	(137)
Net of tax attributable to noncontrolling interests	(3)	[2]
Net of tax attributable to MHFG shareholders	¥ (140)
[1]	The amounts in the Before tax column are recorded in each account presented under the heading "Affected line items in the consolidated statements of income".
[2]	The amounts in the Tax effect column and Net of tax attributable to noncontrolling interests column are recorded in Income tax expense and Net income (loss) attributable to noncontrolling interests in the consolidated statements of 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, 2017	Mar. 31, 2017
Mizuho Financial Group Inc | Consolidated
Common Equity Tier 1 capital:
Required	[1]	¥ 3,856	¥ 3,857
Actual		7,281	7,002
Tier 1 capital:
Required	[1]	4,781	4,783
Actual		¥ 9,005	¥ 8,212
Required	[1]	7.75%	7.75%
Actual		14.59%	13.30%
Total risk-based capital:
Required	[1]	¥ 6,015	¥ 6,017
Actual		¥ 10,947	¥ 10,051
Required	[1]	9.75%	9.75%
Actual		17.74%	16.28%
Common Equity Tier 1 capital:
Required	[1]	6.25%	6.25%
Actual		11.80%	11.34%
Mizuho Bank Limited | Consolidated
Common Equity Tier 1 capital:
Required		¥ 2,525	¥ 2,541
Actual		6,604	6,304
Tier 1 capital:
Required		3,366	3,388
Actual		¥ 8,349	¥ 7,536
Required		6.00%	6.00%
Actual		14.87%	13.34%
Total risk-based capital:
Required		¥ 4,489	¥ 4,517
Actual		¥ 10,193	¥ 9,149
Required		8.00%	8.00%
Actual		18.16%	16.20%
Common Equity Tier 1 capital:
Required		4.50%	4.50%
Actual		11.76%	11.16%
Mizuho Bank Limited | Non-consolidated
Common Equity Tier 1 capital:
Required		¥ 2,417	¥ 2,432
Actual		6,347	6,057
Tier 1 capital:
Required		3,223	3,243
Actual		¥ 8,101	¥ 7,316
Required		6.00%	6.00%
Actual		15.08%	13.53%
Total risk-based capital:
Required		¥ 4,298	¥ 4,324
Actual		¥ 9,949	¥ 8,938
Required		8.00%	8.00%
Actual		18.52%	16.53%
Common Equity Tier 1 capital:
Required		4.50%	4.50%
Actual		11.81%	11.20%
Mizuho Trust & Banking Company Limited | Consolidated
Common Equity Tier 1 capital:
Required		¥ 110	¥ 112
Actual		487	466
Tier 1 capital:
Required		146	149
Actual		¥ 487	¥ 466
Required		6.00%	6.00%
Actual		19.95%	18.73%
Total risk-based capital:
Required		¥ 195	¥ 199
Actual		¥ 505	¥ 485
Required		8.00%	8.00%
Actual		20.68%	19.47%
Common Equity Tier 1 capital:
Required		4.50%	4.50%
Actual		19.95%	18.73%
Mizuho Trust & Banking Company Limited | Non-consolidated
Common Equity Tier 1 capital:
Required		¥ 110	¥ 113
Actual		494	475
Tier 1 capital:
Required		146	150
Actual		¥ 494	¥ 475
Required		6.00%	6.00%
Actual		20.28%	18.98%
Total risk-based capital:
Required		¥ 195	¥ 200
Actual		¥ 511	¥ 493
Required		8.00%	8.00%
Actual		20.99%	19.70%
Common Equity Tier 1 capital:
Required		4.50%	4.50%
Actual		20.28%	18.98%
[1]	The required ratios disclosed above, at March 31, 2017 and September 30, 2017, include the transitional capital conservation buffer of 1.25% and the transitional additional loss absorbency requirements for global systemically important banks ("G-SIBs") and domestic systemically important banks ("D-SIBs") of 0.5%, which are both 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.

Regulatory Matters (Capital A81

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, 2017	Mar. 31, 2017
Japan Gaap Schedule Of Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]
Capital conservation buffer	1.25%	1.25%
March 2,017
Japan Gaap Schedule Of Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]
Additional loss absorbency requirements for G-SIBs and D-SIBs	0.50%	0.50%

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, 2017	Sep. 30, 2016
Net income:
Net income attributable to MHFG shareholders		¥ 372,549	¥ 379,558
Less: Net income attributable to preferred shareholders		0	0
Net income attributable to common shareholders		372,549	379,558
Effect of dilutive securities:
Convertible preferred stock		0	0
Net income attributable to common shareholders after assumed conversions		¥ 372,549	¥ 379,558
Shares:
Weighted average common shares outstanding		25,366,347	25,204,801
Effect of dilutive securities:
Convertible preferred stock	[1]		165,533
Stock options		7,933	11,997
Weighted average common shares after assumed conversions		25,374,280	25,382,331
Amounts per common share:
Basic net income per common share		¥ 14.69	¥ 15.06
Diluted net income per common share		¥ 14.68	¥ 14.95
[1]	The number of common shares after assumed conversion of the convertible preferred stock is based on the applicable conversion prices.

Income Taxes (Components of Inc

Income Taxes (Components of Income Tax Expense) (Detail) - JPY (¥) ¥ in Millions	6 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Reconciliation of Provision of Income Taxes [Line Items]
Current tax expense	¥ 99,238	¥ 102,390
Deferred tax expense (benefit)	20,095	(27,875)
Total income tax expense	¥ 119,333	¥ 74,515

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, 2017	Sep. 30, 2016
Net unrealized gains (losses) on available-for-sale securities:
Unrealized gains (losses)	¥ 105,819	¥ (21,562)
Less: reclassification adjustments	(35,053)	(38,351)
Total	70,766	(59,913)
Foreign currency translation adjustments:
Unrealized gains (losses)		(126)
Less: reclassification adjustments	0	0
Total		(126)
Pension liability adjustments:
Unrealized gains (losses)	11	239
Less: reclassification adjustments	96	87
Total	107	326
Total tax effect before allocation to noncontrolling interests	¥ 70,873	¥ (59,713)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - JPY (¥) ¥ in Millions	6 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Income Taxes [Line Items]
Statutory tax rate	30.86%	30.86%
Effective tax rate	23.27%	16.30%
Net operating loss carryforwards	¥ 1,602,000
Unrecognized tax benefits	1,992
Tax Year 2018
Income Taxes [Line Items]
Net operating loss carryforwards	¥ 861,000
Net operating loss carryforwards, expiration period	Mar. 31, 2018

Pension and Other Employee Be86

Pension and Other Employee Benefit Plans (Summary of Components of Net Periodic Benefit Cost of Severance Indemnities and Pension Plans) (Detail) - JPY (¥) ¥ in Millions	6 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Defined Benefit Plan Disclosure [Line Items]
Service cost-benefits earned during the period	¥ 21,643	¥ 22,219
Interest costs on projected benefit obligations	3,609	2,716
Expected return on plan assets	(17,353)	(17,860)
Amortization of prior service benefits	102	(97)
Amortization of net actuarial loss (gain)	214	385
Special termination benefits	2,128	1,744
Net periodic benefit cost	¥ 10,343	¥ 9,107

Pension and Other Employee Be87

Pension and Other Employee Benefit Plans - Additional Information (Detail) - JPY (¥) ¥ in Billions	6 Months Ended
	Sep. 30, 2017	Mar. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Pension plan, contribution expected to be paid during the next fiscal year		¥ 51
Total payment to pension plans	¥ 25
Additional contribution expected to be paid during remainder of fiscal year	¥ 26

Derivative Financial Instrume88

Derivative Financial Instruments (Summary of Notional and Fair Value Amounts of Derivative Instruments Outstanding) (Detail) - JPY (¥) ¥ in Billions		Sep. 30, 2017	Mar. 31, 2017
Derivatives, Fair Value [Line Items]
Notional amount	[1]	¥ 1,135,201	¥ 1,137,449
Interest rate contracts
Derivatives, Fair Value [Line Items]
Notional amount	[1]	956,180	961,518
Foreign exchange contracts
Derivatives, Fair Value [Line Items]
Notional amount	[1]	169,964	167,698
Equity-related contracts
Derivatives, Fair Value [Line Items]
Notional amount	[1]	5,396	4,177
Credit-related contracts
Derivatives, Fair Value [Line Items]
Notional amount	[1]	3,273	3,696
Other contracts
Derivatives, Fair Value [Line Items]
Notional amount	[1]	388	360
Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Fair value of derivative receivables	[2]		2
Fair value of derivative payables	[2]	19	5
Designated as Hedging Instrument | Foreign exchange contracts
Derivatives, Fair Value [Line Items]
Fair value of derivative receivables	[2]		2
Fair value of derivative payables	[2]	5
Designated as Hedging Instrument | Equity-related contracts
Derivatives, Fair Value [Line Items]
Fair value of derivative payables	[2]	14	5
Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Fair value of derivative receivables	[2]	10,344	11,441
Fair value of derivative payables	[2]	10,357	11,366
Not Designated as Hedging Instrument | Interest rate contracts
Derivatives, Fair Value [Line Items]
Fair value of derivative receivables	[2]	7,662	8,506
Fair value of derivative payables	[2]	7,658	8,473
Not Designated as Hedging Instrument | Foreign exchange contracts
Derivatives, Fair Value [Line Items]
Fair value of derivative receivables	[2]	2,484	2,743
Fair value of derivative payables	[2]	2,393	2,611
Not Designated as Hedging Instrument | Equity-related contracts
Derivatives, Fair Value [Line Items]
Fair value of derivative receivables	[2]	151	134
Fair value of derivative payables	[2]	258	224
Not Designated as Hedging Instrument | Credit-related contracts
Derivatives, Fair Value [Line Items]
Fair value of derivative receivables	[2]	29	35
Fair value of derivative payables	[2]	31	36
Not Designated as Hedging Instrument | Other contracts
Derivatives, Fair Value [Line Items]
Fair value of derivative receivables	[2]	18	23
Fair value of derivative payables	[2]	¥ 17	¥ 22
[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 Instrume89

Derivative Financial Instruments - Additional Information (Detail) - JPY (¥) ¥ in Millions	Sep. 30, 2017	Mar. 31, 2017
Derivative [Line Items]
Cash collateral provided and not offset against derivative positions and included in Other assets	¥ 1,110,240	¥ 973,404
Cash collateral accepted and not offset against derivative positions and included in Other liabilities	¥ 568,881	¥ 671,691

Derivative Financial Instrume90

Derivative Financial Instruments (Summary of Gains and Losses Information Related to Fair Value Hedges) (Detail) - JPY (¥) ¥ in Millions	6 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recorded in income- Derivatives	¥ (22,493)	¥ 6,002
Gains (losses) recorded in income- Hedged items	20,208	(7,807)
Gains (losses) recorded in income- Hedge ineffectiveness	0	0
Gains (losses) recorded in income- Net gain (loss) excluded from assessment of effectiveness	(2,285)	(1,805)
Equity-related contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recorded in income- Derivatives	(22,493)	6,002
Gains (losses) recorded in income- Hedged items	20,208	(7,807)
Gains (losses) recorded in income- Hedge ineffectiveness	0	0
Gains (losses) recorded in income- Net gain (loss) excluded from assessment of effectiveness	¥ (2,285)	¥ (1,805)

Derivative Financial Instrume91

Derivative Financial Instruments (Summary of Gains and Losses Information Related to Net Investment Hedges) (Detail) - JPY (¥) ¥ in Millions	6 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Effective portion recorded in OCI	¥ 3,487	¥ 107,528
Ineffective portion recorded in income	196	890
Financial instruments hedging foreign exchange risk
Derivative Instruments, Gain (Loss) [Line Items]
Effective portion recorded in OCI	3,487	107,528
Ineffective portion recorded in income	¥ 196	¥ 890

Derivative Financial Instrume92

Derivative Financial Instruments (Summary of Gains and Losses Information Related to Net Investment Hedges) (Parenthetical) (Detail) - JPY (¥)	Sep. 30, 2017	Sep. 30, 2016
Financial instruments hedging foreign exchange risk
Derivative Instruments, Gain (Loss) [Line Items]
Accumulated other comprehensive income reclassified to earnings	¥ 0	¥ 0

Derivative Financial Instrume93

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, 2017	Sep. 30, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recorded in income		¥ (22,609)	¥ 97,999
Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recorded in income		26,648	80,040
Foreign exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recorded in income		(4,511)	11,173
Equity-related contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recorded in income	[1]	(41,869)	11,049
Credit-related contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recorded in income	[2]	(3,371)	(4,827)
Other contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recorded in income		¥ 494	¥ 564
[1]	The net gain (loss) excluded from the assessment of the effectiveness of fair value hedges is not included in the above table.
[2]	Amounts include the net gain (loss) of ¥(5,698) million and ¥(273) million on the credit derivatives hedging the credit risk of loans during the six months ended September 30, 2016 and 2017, respectively.

Derivative Financial Instrume94

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, 2017	Sep. 30, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recorded in income		¥ (22,609)	¥ 97,999
Credit-related contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recorded in income	[1]	(3,371)	(4,827)
Credit-related contracts | Loans related to credit derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recorded in income		¥ (273)	¥ (5,698)
[1]	Amounts include the net gain (loss) of ¥(5,698) million and ¥(273) million on the credit derivatives hedging the credit risk of loans during the six months ended September 30, 2016 and 2017, respectively.

Derivative Financial Instrume95

Derivative Financial Instruments (Summary of Notional and Fair Value Amounts of Credit Derivatives) (Detail) - JPY (¥) ¥ in Billions	Sep. 30, 2017	Mar. 31, 2017
Credit protection written
Credit Derivatives [Line Items]
Notional amount	¥ 1,573	¥ 1,844
Fair value	24	22
Credit protection written | Investment grade
Credit Derivatives [Line Items]
Notional amount	1,371	1,546
Fair value	23	21
Credit protection written | Non-investment grade
Credit Derivatives [Line Items]
Notional amount	202	298
Fair value	1	1
Credit protection purchased
Credit Derivatives [Line Items]
Notional amount	1,727	1,994
Fair value	¥ (26)	¥ (23)

Derivative Financial Instrume96

Derivative Financial Instruments (Maximum Potential Amount of Future Payments for Credit Protection Written by Expiration Period) (Detail) - JPY (¥) ¥ in Billions	Sep. 30, 2017	Mar. 31, 2017
Credit Derivatives [Line Items]
Maximum payout/Notional amount	¥ 1,573	¥ 1,844
One year or less
Credit Derivatives [Line Items]
Maximum payout/Notional amount	406	507
After one year through five years
Credit Derivatives [Line Items]
Maximum payout/Notional amount	926	1,020
After five years
Credit Derivatives [Line Items]
Maximum payout/Notional amount	¥ 241	¥ 317

Derivative Financial Instrume97

Derivative Financial Instruments (Quantitative Information about Derivative Instruments with Credit-risk-related Contingent Features) (Detail) - JPY (¥) ¥ in Billions	Sep. 30, 2017	Mar. 31, 2017
Credit Derivatives [Line Items]
Aggregate fair value of derivative instruments with credit-risk-related contingent features in net liability positions	¥ 755	¥ 698
Collateral provided to counterparties in the normal course of business	729	658
Amount required to be posted as collateral or settled immediately if credit-risk-related contingent features were triggered	¥ 26	¥ 40

Commitments and Contingencies98

Commitments and Contingencies (Summary of Maximum Potential Amount of Future Payments by Type of Guarantee) (Detail) - JPY (¥) ¥ in Billions	Sep. 30, 2017	Mar. 31, 2017
Performance guarantees
Guarantor Obligations [Line Items]
Maximum potential/Contractual or Notional amount	¥ 2,363	¥ 2,243
Guarantees on loans
Guarantor Obligations [Line Items]
Maximum potential/Contractual or Notional amount	259	278
Guarantees on securities
Guarantor Obligations [Line Items]
Maximum potential/Contractual or Notional amount	174	175
Other guarantees
Guarantor Obligations [Line Items]
Maximum potential/Contractual or Notional amount	1,933	1,823
Guarantees for repayment of trust principal
Guarantor Obligations [Line Items]
Maximum potential/Contractual or Notional amount	642	730
Liabilities of trust accounts
Guarantor Obligations [Line Items]
Maximum potential/Contractual or Notional amount	15,288	15,177
Derivative financial instruments
Guarantor Obligations [Line Items]
Maximum potential/Contractual or Notional amount	¥ 13,080	¥ 14,415

Commitments and Contingencies99

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, 2017	Mar. 31, 2017
Guarantor Obligations [Line Items]
Maximum potential/Contractual or Notional amount		¥ 4,729	¥ 4,519
Investment grade
Guarantor Obligations [Line Items]
Maximum potential/Contractual or Notional amount	[1]	3,808	3,477
Non-investment grade
Guarantor Obligations [Line Items]
Maximum potential/Contractual or Notional amount		¥ 921	¥ 1,042
[1]	Investment grade in the internal rating scale generally corresponds to BBB- or above in the external rating scale.

Commitments and Contingencie100

Commitments and Contingencies (Summary of Contractual Amounts with Regard to Undrawn Commitments) (Detail) - JPY (¥) ¥ in Billions		Sep. 30, 2017	Mar. 31, 2017
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Off-balance-sheet instruments, contractual amounts of the undrawn commitments		¥ 77,722	¥ 77,200
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]	77,100	76,678
Commercial letters of credit
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Off-balance-sheet instruments, contractual amounts of the undrawn commitments		¥ 622	¥ 522
[1]	Commitments to extend credit include commitments to invest in securities.

Variable Interest Entities a101

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 Billions	Sep. 30, 2017	Mar. 31, 2017
Variable Interest Entity [Line Items]
Consolidated VIEs- Consolidated assets	¥ 5,134	¥ 5,246
Significant unconsolidated VIEs- Total assets	4,483	4,448
Significant unconsolidated VIEs- Maximum exposure to loss	705	628
Asset-backed commercial paper/loan programs
Variable Interest Entity [Line Items]
Consolidated VIEs- Consolidated assets	1,863	2,031
Asset-backed securitizations
Variable Interest Entity [Line Items]
Consolidated VIEs- Consolidated assets	626	629
Significant unconsolidated VIEs- Total assets	66	108
Significant unconsolidated VIEs- Maximum exposure to loss	11	11
Investments in securitization products
Variable Interest Entity [Line Items]
Consolidated VIEs- Consolidated assets	374	375
Significant unconsolidated VIEs- Total assets	136	445
Significant unconsolidated VIEs- Maximum exposure to loss	80	154
Investment funds
Variable Interest Entity [Line Items]
Consolidated VIEs- Consolidated assets	2,249	2,188
Significant unconsolidated VIEs- Total assets	4,281	3,895
Significant unconsolidated VIEs- Maximum exposure to loss	614	463
Trust arrangements and other
Variable Interest Entity [Line Items]
Consolidated VIEs- Consolidated assets	¥ 22	¥ 23

Variable Interest Entities a102

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, 2017	Mar. 31, 2017
Assets on balance sheets related to unconsolidated VIEs:
Trading account assets		¥ 27,457,300	¥ 24,998,493
Loans		83,532,990	81,804,233
Total		208,977,063	200,456,304
Liabilities on balance sheets and maximum exposure to loss related to unconsolidated VIEs:
Payables under securities lending transactions		2,873,259	1,919,249
Trading account liabilities		12,945,086	13,591,740
Total		199,776,302	191,684,247
Maximum exposure to loss		705,000	628,000
Unconsolidated VIEs
Assets on balance sheets related to unconsolidated VIEs:
Trading account assets		100,000	85,000
Investments		386,000	254,000
Loans		168,000	237,000
Total		654,000	576,000
Liabilities on balance sheets and maximum exposure to loss related to unconsolidated VIEs:
Payables under securities lending transactions		37,000	31,000
Trading account liabilities		1,000	1,000
Total		38,000	32,000
Maximum exposure to loss	[1]	¥ 705,000	¥ 628,000
[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 a103

Variable Interest Entities and Securitizations - Additional Information (Detail) - JPY (¥) ¥ in Millions	Sep. 30, 2017	Mar. 31, 2017	Apr. 01, 2016
Variable Interest Entity [Line Items]
Decrease to the beginning balance of retained earnings			¥ (329)
Iincrease to the beginning balance of Accumulated other comprehensive income			330
Total assets	¥ 208,977,063	¥ 200,456,304
Noncontrolling interests	499,161	510,700
Total liabilities	199,776,302	191,684,247
Consolidated certain investment funds | Restatement Adjustment
Variable Interest Entity [Line Items]
Total assets			16,000
Noncontrolling interests			16,000
Deconsolidated certain investment funds | Restatement Adjustment
Variable Interest Entity [Line Items]
Total assets			(54,000)
Noncontrolling interests			(27,000)
Total liabilities			¥ (27,000)
Assets associated with securitization transactions
Variable Interest Entity [Line Items]
Transferred assets continue to be carried on the consolidated balance sheets	235,000	244,000
Assets associated with loan participation transactions
Variable Interest Entity [Line Items]
Transferred assets continue to be carried on the consolidated balance sheets	¥ 113,000	¥ 91,000

Fee and Commission Income (Deta

Fee and Commission Income (Details of Fees and Commission Income) (Detail) - JPY (¥) ¥ in Millions	6 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Principal Transaction Revenue [Line Items]
Securities-related business	¥ 85,897	¥ 75,145
Deposits and lending business	65,081	85,340
Remittance business	54,166	53,858
Asset management business	50,322	29,548
Trust fees	25,966	23,134
Fees for other customer services	119,799	125,437
Total	¥ 401,231	¥ 392,462

Fair Value - Additional Informa

Fair Value - Additional Information (Detail) - JPY (¥) ¥ in Billions	6 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Mar. 31, 2017
Fair Value, Estimate Not Practicable, Financial Statement Captions [Line Items]
Carrying amounts of other equity interests of which fair value is not readily determinable	¥ 243		¥ 308
Senior borrowings and bonds
Fair Value, Estimate Not Practicable, Financial Statement Captions [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	8		¥ 36
Net unrealized gains (losses) resulting from changes in fair values of the notes	¥ (28)	¥ 2
Investment funds
Fair Value, Estimate Not Practicable, Financial Statement Captions [Line Items]
Underlying assets, estimated remaining liquidation period	10 years
Long-term debt
Fair Value, Estimate Not Practicable, Financial Statement Captions [Line Items]
Fair value of liabilities transferred into Level 3	¥ 1
Fair value of liabilities transferred out of Level 3	10	12
Trading securities sold, not yet purchased
Fair Value, Estimate Not Practicable, Financial Statement Captions [Line Items]
Fair value of liabilities transferred into Level 3		1
Trading securities
Fair Value, Estimate Not Practicable, Financial Statement Captions [Line Items]
Fair value of assets transferred into Level 3	123	280
Fair value of assets transferred out of Level 3	240	¥ 2
Available-for-sale securities
Fair Value, Estimate Not Practicable, Financial Statement Captions [Line Items]
Fair value of assets transferred into Level 3	15
Fair value of assets transferred out of Level 3	¥ 29

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, 2017	Mar. 31, 2017
Assets:
Available-for-sale securities		¥ 20,152,046	¥ 20,557,118
Liabilities:
Long-term debt		1,943,986	1,496,488
Fair Value, Measurements, Recurring
Assets:
Other investments		39,000	37,000
Total assets measured at fair value		47,648,000	45,592,000
Liabilities:
Trading securities sold, not yet purchased		2,569,000	2,221,000
Long-term debt	[1]	1,944,000	1,496,000
Total liabilities measured at fair value		14,889,000	15,088,000
Fair Value, Measurements, Recurring | Trading securities
Assets:
Securities measured at net asset value	[2]	681,000	678,000
Fair Value, Measurements, Recurring | Interest rate contracts
Assets:
Assets, derivatives		7,662,000	8,506,000
Liabilities:
Liabilities, derivatives		7,658,000	8,473,000
Fair Value, Measurements, Recurring | Foreign exchange contracts
Assets:
Assets, derivatives		2,484,000	2,745,000
Liabilities:
Liabilities, derivatives		2,398,000	2,611,000
Fair Value, Measurements, Recurring | Equity-related contracts
Assets:
Assets, derivatives		151,000	134,000
Liabilities:
Liabilities, derivatives		272,000	229,000
Fair Value, Measurements, Recurring | Credit-related contracts
Assets:
Assets, derivatives		29,000	35,000
Liabilities:
Liabilities, derivatives		31,000	36,000
Fair Value, Measurements, Recurring | Other contracts
Assets:
Assets, derivatives		18,000	23,000
Liabilities:
Liabilities, derivatives		17,000	22,000
Fair Value, Measurements, Recurring | Japanese government bonds
Assets:
Assets, trading securities	[3]	3,041,000	1,508,000
Available-for-sale securities		9,658,000	10,263,000
Fair Value, Measurements, Recurring | Japanese local government bonds
Assets:
Assets, trading securities	[3]	48,000	69,000
Available-for-sale securities		254,000	284,000
Fair Value, Measurements, Recurring | U.S. Treasury bonds and federal agency securities
Assets:
Assets, trading securities	[3]	4,127,000	2,963,000
Available-for-sale securities		850,000	1,144,000
Fair Value, Measurements, Recurring | Other foreign government bonds
Assets:
Assets, trading securities	[3]	1,817,000	1,584,000
Available-for-sale securities		972,000	935,000
Fair Value, Measurements, Recurring | Agency mortgage-backed securities
Assets:
Assets, trading securities	[3]	2,006,000	1,973,000
Available-for-sale securities		891,000	843,000
Fair Value, Measurements, Recurring | Residential mortgage-backed securities
Assets:
Assets, trading securities	[3]	14,000	15,000
Available-for-sale securities		137,000	144,000
Fair Value, Measurements, Recurring | Commercial mortgage-backed securities
Assets:
Assets, trading securities	[3]		3,000
Available-for-sale securities		257,000	224,000
Fair Value, Measurements, Recurring | Certificates of deposit and commercial paper
Assets:
Assets, trading securities	[3]	708,000	554,000
Fair Value, Measurements, Recurring | Corporate bonds and other debt securities
Assets:
Assets, trading securities	[3]	3,024,000	2,504,000
Fair Value, Measurements, Recurring | Equity securities
Assets:
Assets, trading securities	[3]	1,647,000	1,704,000
Fair Value, Measurements, Recurring | Japanese corporate bonds and other debt securities
Assets:
Available-for-sale securities		1,950,000	2,008,000
Fair Value, Measurements, Recurring | Foreign corporate bonds and other debt securities
Assets:
Available-for-sale securities		890,000	911,000
Fair Value, Measurements, Recurring | Equity securities (marketable)
Assets:
Available-for-sale securities		4,293,000	3,801,000
Fair Value, Measurements, Recurring | Level 1
Assets:
Total assets measured at fair value		25,749,000	23,475,000
Liabilities:
Trading securities sold, not yet purchased		2,296,000	1,993,000
Total liabilities measured at fair value		2,514,000	2,189,000
Fair Value, Measurements, Recurring | Level 1 | Interest rate contracts
Assets:
Assets, derivatives		40,000	37,000
Liabilities:
Liabilities, derivatives		39,000	46,000
Fair Value, Measurements, Recurring | Level 1 | Foreign exchange contracts
Assets:
Assets, derivatives		20,000	28,000
Liabilities:
Liabilities, derivatives		16,000	20,000
Fair Value, Measurements, Recurring | Level 1 | Equity-related contracts
Assets:
Assets, derivatives		40,000	31,000
Liabilities:
Liabilities, derivatives		161,000	129,000
Fair Value, Measurements, Recurring | Level 1 | Other contracts
Assets:
Assets, derivatives		2,000	1,000
Liabilities:
Liabilities, derivatives		2,000	1,000
Fair Value, Measurements, Recurring | Level 1 | Japanese government bonds
Assets:
Assets, trading securities	[3]	3,012,000	1,485,000
Available-for-sale securities		8,926,000	9,543,000
Fair Value, Measurements, Recurring | Level 1 | U.S. Treasury bonds and federal agency securities
Assets:
Assets, trading securities	[3]	3,832,000	2,883,000
Available-for-sale securities		850,000	1,144,000
Fair Value, Measurements, Recurring | Level 1 | Other foreign government bonds
Assets:
Assets, trading securities	[3]	1,368,000	1,127,000
Available-for-sale securities		364,000	346,000
Fair Value, Measurements, Recurring | Level 1 | Agency mortgage-backed securities
Assets:
Assets, trading securities	[3]	1,264,000	1,335,000
Available-for-sale securities		161,000	134,000
Fair Value, Measurements, Recurring | Level 1 | Corporate bonds and other debt securities
Assets:
Assets, trading securities	[3]	9,000	3,000
Fair Value, Measurements, Recurring | Level 1 | Equity securities
Assets:
Assets, trading securities	[3]	1,625,000	1,661,000
Fair Value, Measurements, Recurring | Level 1 | Equity securities (marketable)
Assets:
Available-for-sale securities		4,236,000	3,717,000
Fair Value, Measurements, Recurring | Level 2
Assets:
Total assets measured at fair value		19,413,000	19,665,000
Liabilities:
Trading securities sold, not yet purchased		269,000	228,000
Long-term debt	[1]	1,381,000	903,000
Total liabilities measured at fair value		11,753,000	12,253,000
Fair Value, Measurements, Recurring | Level 2 | Interest rate contracts
Assets:
Assets, derivatives		7,600,000	8,442,000
Liabilities:
Liabilities, derivatives		7,618,000	8,426,000
Fair Value, Measurements, Recurring | Level 2 | Foreign exchange contracts
Assets:
Assets, derivatives		2,458,000	2,709,000
Liabilities:
Liabilities, derivatives		2,382,000	2,591,000
Fair Value, Measurements, Recurring | Level 2 | Equity-related contracts
Assets:
Assets, derivatives		93,000	89,000
Liabilities:
Liabilities, derivatives		67,000	61,000
Fair Value, Measurements, Recurring | Level 2 | Credit-related contracts
Assets:
Assets, derivatives		27,000	33,000
Liabilities:
Liabilities, derivatives		29,000	34,000
Fair Value, Measurements, Recurring | Level 2 | Other contracts
Assets:
Assets, derivatives		7,000	11,000
Liabilities:
Liabilities, derivatives		7,000	10,000
Fair Value, Measurements, Recurring | Level 2 | Japanese government bonds
Assets:
Assets, trading securities	[3]	29,000	23,000
Available-for-sale securities		732,000	720,000
Fair Value, Measurements, Recurring | Level 2 | Japanese local government bonds
Assets:
Assets, trading securities	[3]	48,000	69,000
Available-for-sale securities		254,000	284,000
Fair Value, Measurements, Recurring | Level 2 | U.S. Treasury bonds and federal agency securities
Assets:
Assets, trading securities	[3]	295,000	80,000
Fair Value, Measurements, Recurring | Level 2 | Other foreign government bonds
Assets:
Assets, trading securities	[3]	449,000	457,000
Available-for-sale securities		608,000	589,000
Fair Value, Measurements, Recurring | Level 2 | Agency mortgage-backed securities
Assets:
Assets, trading securities	[3]	742,000	638,000
Available-for-sale securities		730,000	709,000
Fair Value, Measurements, Recurring | Level 2 | Residential mortgage-backed securities
Assets:
Available-for-sale securities		69,000	67,000
Fair Value, Measurements, Recurring | Level 2 | Commercial mortgage-backed securities
Assets:
Assets, trading securities	[3]		3,000
Fair Value, Measurements, Recurring | Level 2 | Certificates of deposit and commercial paper
Assets:
Assets, trading securities	[3]	708,000	554,000
Fair Value, Measurements, Recurring | Level 2 | Corporate bonds and other debt securities
Assets:
Assets, trading securities	[3]	1,929,000	1,449,000
Fair Value, Measurements, Recurring | Level 2 | Equity securities
Assets:
Assets, trading securities	[3]		20,000
Fair Value, Measurements, Recurring | Level 2 | Japanese corporate bonds and other debt securities
Assets:
Available-for-sale securities		1,785,000	1,834,000
Fair Value, Measurements, Recurring | Level 2 | Foreign corporate bonds and other debt securities
Assets:
Available-for-sale securities		793,000	801,000
Fair Value, Measurements, Recurring | Level 2 | Equity securities (marketable)
Assets:
Available-for-sale securities		57,000	84,000
Fair Value, Measurements, Recurring | Level 3
Assets:
Other investments		39,000	37,000
Total assets measured at fair value		1,805,000	1,774,000
Liabilities:
Trading securities sold, not yet purchased		4,000
Long-term debt	[1]	563,000	593,000
Total liabilities measured at fair value		622,000	646,000
Fair Value, Measurements, Recurring | Level 3 | Interest rate contracts
Assets:
Assets, derivatives		22,000	27,000
Liabilities:
Liabilities, derivatives		1,000	1,000
Fair Value, Measurements, Recurring | Level 3 | Foreign exchange contracts
Assets:
Assets, derivatives		6,000	8,000
Fair Value, Measurements, Recurring | Level 3 | Equity-related contracts
Assets:
Assets, derivatives		18,000	14,000
Liabilities:
Liabilities, derivatives		44,000	39,000
Fair Value, Measurements, Recurring | Level 3 | Credit-related contracts
Assets:
Assets, derivatives		2,000	2,000
Liabilities:
Liabilities, derivatives		2,000	2,000
Fair Value, Measurements, Recurring | Level 3 | Other contracts
Assets:
Assets, derivatives		9,000	11,000
Liabilities:
Liabilities, derivatives		8,000	11,000
Fair Value, Measurements, Recurring | Level 3 | Residential mortgage-backed securities
Assets:
Assets, trading securities	[3]	14,000	15,000
Available-for-sale securities		68,000	77,000
Fair Value, Measurements, Recurring | Level 3 | Commercial mortgage-backed securities
Assets:
Available-for-sale securities		257,000	224,000
Fair Value, Measurements, Recurring | Level 3 | Corporate bonds and other debt securities
Assets:
Assets, trading securities	[3]	1,086,000	1,052,000
Fair Value, Measurements, Recurring | Level 3 | Equity securities
Assets:
Assets, trading securities	[3]	22,000	23,000
Fair Value, Measurements, Recurring | Level 3 | Japanese corporate bonds and other debt securities
Assets:
Available-for-sale securities		165,000	174,000
Fair Value, Measurements, Recurring | Level 3 | Foreign corporate bonds and other debt securities
Assets:
Available-for-sale securities		¥ 97,000	¥ 110,000
[1]	Amounts represent items for which the Group elected the fair value option.
[2]	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, 2017 and September 30, 2017 were ¥33 billion and ¥29 billion, respectively.
[3]	Trading securities include foreign currency denominated securities for which the MHFG Group elected the fair value option.

Fair Value (Summary of Asset107

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, 2017	Mar. 31, 2017
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unfunded commitments	¥ 29	¥ 33

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, 2017	Sep. 30, 2016
Other investments
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance		¥ 37	¥ 42
Gains (losses) in Earnings	[1]		(3)
Purchases		12	11
Issuances		0	0
Settlements		(10)	(13)
Ending Balance		39	37
Change in unrealized gain (losses) still held	[2]		(1)
Trading securities sold, not yet purchased
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Gains (losses) in OCI		0	0
Transfers into Level 3			1
Purchases		(57)	(32)
Sales		61	32
Ending Balance		4	1
Long-term debt
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance		593	623
Gains (losses) in Earnings	[3]	(13)	9
Gains (losses) in OCI		0	0
Transfers into Level 3		1
Transfers out of level 3		(10)	(12)
Issuances		47	147
Settlements		(81)	(158)
Ending Balance		563	591
Change in unrealized gain (losses) still held	[2]	(14)	5
Trading securities
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers into Level 3		123	280
Transfers out of level 3		(240)	(2)
Trading securities | Residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance		15	21
Issuances		0	0
Settlements		(1)	(4)
Ending Balance		14	17
Trading securities | Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance			2
Issuances			0
Settlements			(2)
Trading securities | Corporate bonds and other debt securities
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance		1,052	720
Gains (losses) in Earnings	[4]	18	(53)
Transfers into Level 3		123	280
Transfers out of level 3		(240)	(2)
Purchases		562	343
Sales		(276)	(241)
Issuances		0	0
Settlements		(153)	(71)
Ending Balance		1,086	976
Change in unrealized gain (losses) still held	[2]	20	(39)
Trading securities | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance		23	21
Gains (losses) in Earnings	[4]	(1)	4
Sales			(7)
Issuances		0	0
Ending Balance		22	18
Change in unrealized gain (losses) still held	[2]	(1)	4
Derivative assets | Interest rate contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	[5]	26	26
Gains (losses) in Earnings	[4],[5]	(6)	(4)
Issuances	[5]	0	0
Settlements	[5]	1
Ending Balance	[5]	21	22
Change in unrealized gain (losses) still held	[2],[5]	(6)	(3)
Derivative assets | Foreign exchange contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	[5]	8	7
Gains (losses) in Earnings	[4],[5]	(2)	6
Issuances	[5]	0	0
Settlements	[5]		(7)
Ending Balance	[5]	6	6
Change in unrealized gain (losses) still held	[2],[5]	(2)
Derivative assets | Equity-related contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	[5]	(25)	5
Gains (losses) in Earnings	[4],[5]	(7)	(13)
Issuances	[5]	0	0
Settlements	[5]	6	(2)
Ending Balance	[5]	(26)	(10)
Change in unrealized gain (losses) still held	[2],[5]	(8)	(19)
Derivative assets | Credit-related contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	[5]		(1)
Gains (losses) in Earnings	[4],[5]		1
Issuances	[5]		0
Derivative assets | Other contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	[5]		1
Issuances	[5]	0	0
Settlements	[5]	1
Ending Balance	[5]	1	1
Available-for-sale securities
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers into Level 3		15
Transfers out of level 3		(29)
Available-for-sale securities | Residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance		77	123
Purchases		1
Sales			(1)
Issuances		0	0
Settlements		(10)	(22)
Ending Balance		68	100
Available-for-sale securities | Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance		224	187
Purchases		40	20
Sales		(7)
Issuances		0	0
Settlements			(9)
Ending Balance		257	198
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		174	174
Gains (losses) in Earnings	[1]	(1)
Gains (losses) in OCI	[6]	(3)	22
Purchases		11	1
Sales			(4)
Issuances		0	0
Settlements		(16)	(17)
Ending Balance		165	176
Change in unrealized gain (losses) still held	[2]	(1)
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		110	108
Gains (losses) in Earnings	[1]		1
Gains (losses) in OCI	[6]	1	(7)
Transfers into Level 3		15
Transfers out of level 3		(29)
Purchases			10
Issuances		0	0
Settlements			(5)
Ending Balance		¥ 97	¥ 107
[1]	Gains (losses) in Earnings are reported in Investment gains (losses)-net.
[2]	Amounts represent total gains or losses recognized in earnings 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, 2016 and 2017.
[3]	Gains (losses) in Earnings are reported in Other noninterest income (expenses).
[4]	Gains (losses) in Earnings are reported in Trading account gains (losses)-net, Foreign exchange gains (losses)-net or Other noninterest income (expenses).
[5]	Total Level 3 derivative exposures have been netted on the table for presentation purposes only.
[6]	Gains (losses) in OCI are reported in Other comprehensive income (loss).

Fair Value (Quantitative Inform

Fair Value (Quantitative Information about Significant Unobservable Inputs Related to Material Classes of Level 3 Assets and Liabilities) (Detail) - JPY (¥) ¥ in Billions		6 Months Ended	12 Months Ended
		Sep. 30, 2017	Mar. 31, 2017
Available For Sale And Trading Securities | Residential mortgage-backed securities
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair value		¥ 82	¥ 92
Principal valuation technique		Discounted cash flow Price-based
Available For Sale And Trading Securities | Residential mortgage-backed securities | Discounted Cash Flow Method Or Transaction Price Valuation Technique | Weighted Average
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Prepayment rate	[1]	7.00%	7.00%
Default rate	[1]	0.00%	0.00%
Recovery rate	[1]	100.00%	100.00%
Discount margin	[1]	0.56%	0.55%
Available For Sale And Trading Securities | Residential mortgage-backed securities | Discounted Cash Flow Method Or Transaction Price Valuation Technique | Minimum
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Prepayment rate		3.00%	0.00%
Default rate		0.00%	0.00%
Recovery rate		100.00%	100.00%
Discount margin		0.14%	0.15%
Available For Sale And Trading Securities | Residential mortgage-backed securities | Discounted Cash Flow Method Or Transaction Price Valuation Technique | Maximum
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Prepayment rate		17.00%	18.00%
Default rate		1.00%	1.00%
Recovery rate		100.00%	100.00%
Discount margin		1.70%	1.70%
Available For Sale And Trading Securities | Commercial mortgage-backed securities
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair value		¥ 257	¥ 224
Principal valuation technique		Discounted cash flow Price-based
Available For Sale And Trading Securities | Commercial mortgage-backed securities | Discounted Cash Flow Method Or Transaction Price Valuation Technique | Weighted Average
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Discount margin	[1]	0.27%	0.28%
Available For Sale And Trading Securities | Commercial mortgage-backed securities | Discounted Cash Flow Method Or Transaction Price Valuation Technique | Minimum
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Discount margin		0.02%	0.04%
Available For Sale And Trading Securities | Commercial mortgage-backed securities | Discounted Cash Flow Method Or Transaction Price Valuation Technique | Maximum
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Discount margin		0.93%	2.05%
Available For Sale And Trading Securities | Corporate bonds and other debt securities
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair value		¥ 1,348	¥ 1,336
Principal valuation technique		Discounted cash flow Price-based
Available For Sale And Trading Securities | Corporate bonds and other debt securities | Discounted Cash Flow Method Or Transaction Price Valuation Technique | Weighted Average
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Prepayment rate	[1],[2]	39.00%	29.00%
Default rate	[1],[2]	2.00%	2.00%
Recovery rate	[1],[2]	68.00%	68.00%
Discount margin	[1],[2]	1.22%	1.31%
Available For Sale And Trading Securities | Corporate bonds and other debt securities | Discounted Cash Flow Method Or Transaction Price Valuation Technique | Minimum
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Prepayment rate	[2]	22.00%	16.00%
Default rate	[2]	1.00%	1.00%
Recovery rate	[2]	60.00%	60.00%
Discount margin	[2]	0.16%	0.08%
Available For Sale And Trading Securities | Corporate bonds and other debt securities | Discounted Cash Flow Method Or Transaction Price Valuation Technique | Maximum
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Prepayment rate	[2]	39.00%	30.00%
Default rate	[2]	2.00%	2.00%
Recovery rate	[2]	68.00%	68.00%
Discount margin	[2]	11.79%	11.81%
Available For Sale And Trading Securities | Japanese corporate bonds and foreign corporate bonds | Discounted Cash Flow Method Or Transaction Price Valuation Technique | Weighted Average
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Discount margin	[1],[3]	4.22%	3.59%
Available For Sale And Trading Securities | Japanese corporate bonds and foreign corporate bonds | Discounted Cash Flow Method Or Transaction Price Valuation Technique | Minimum
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Discount margin	[3]	0.02%	0.10%
Available For Sale And Trading Securities | Japanese corporate bonds and foreign corporate bonds | Discounted Cash Flow Method Or Transaction Price Valuation Technique | Maximum
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Discount margin	[3]	11.67%	9.39%
Derivative contracts | Interest rate contracts
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair value		¥ 21	¥ 26
Principal valuation technique	[4]	Internal valuation model
Derivative contracts | Interest rate contracts | Internal Valuation Model | Minimum
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
IR - IR correlation		23.00%	23.00%
Default rate	[5]	0.00%	0.00%
Derivative contracts | Interest rate contracts | Internal Valuation Model | Maximum
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
IR - IR correlation		100.00%	100.00%
Default rate	[5]	63.00%	63.00%
Derivative contracts | Foreign exchange contracts
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair value		¥ 6	¥ 8
Principal valuation technique	[4]	Internal valuation model
Derivative contracts | Foreign exchange contracts | Internal Valuation Model | Minimum
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
FX - IR correlation		5.00%	5.00%
FX - FX correlation		59.00%	55.00%
Default rate	[5]	0.00%	0.00%
Derivative contracts | Foreign exchange contracts | Internal Valuation Model | Maximum
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
FX - IR correlation		54.00%	52.00%
FX - FX correlation		59.00%	55.00%
Default rate	[5]	63.00%	63.00%
Derivative contracts | Equity-related contracts
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair value		¥ (26)	¥ (25)
Principal valuation technique	[4]	Internal valuation model
Derivative contracts | Equity-related contracts | Internal Valuation Model | Minimum
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Equity - IR correlation		25.00%	25.00%
Equity - FX correlation		55.00%	55.00%
Equity volatility		11.00%	6.00%
Derivative contracts | Equity-related contracts | Internal Valuation Model | Maximum
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Equity - IR correlation		25.00%	25.00%
Equity - FX correlation		55.00%	55.00%
Equity volatility		58.00%	59.00%
Derivative contracts | Credit-related contracts
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Principal valuation technique	[4]	Internal valuation model
Derivative contracts | Credit-related contracts | Internal Valuation Model | Minimum
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Default rate		0.00%	0.00%
Credit correlation		26.00%	30.00%
Derivative contracts | Credit-related contracts | Internal Valuation Model | Maximum
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Default rate		3.00%	5.00%
Credit correlation		100.00%	100.00%
Long-term debt
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair value		¥ 563	¥ 593
Principal valuation technique	[4]	Internal valuation model
Long-term debt | Internal Valuation Model | Minimum
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
IR - IR correlation		23.00%	23.00%
FX - IR correlation		5.00%	5.00%
FX - FX correlation		59.00%	55.00%
Default rate		0.00%	0.00%
Equity - IR correlation		25.00%	25.00%
Credit correlation		32.00%	33.00%
Equity - FX correlation		55.00%	55.00%
Equity volatility		9.00%	5.00%
Equity correlation		19.00%	20.00%
Long-term debt | Internal Valuation Model | Maximum
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
IR - IR correlation		100.00%	100.00%
FX - IR correlation		54.00%	52.00%
FX - FX correlation		59.00%	55.00%
Default rate		2.00%	3.00%
Equity - IR correlation		25.00%	25.00%
Credit correlation		100.00%	100.00%
Equity - FX correlation		55.00%	55.00%
Equity volatility		34.00%	40.00%
Equity correlation		100.00%	100.00%
[1]	Weighted averages are calculated by weighting each input by the relative fair value of the respective financial instruments.
[2]	These inputs are mainly used for determining the fair values of securitization products such as CDO, CLO and ABS, other than RMBS and CMBS.
[3]	This input is mainly used for determining the fair values of Japanese corporate bonds and foreign corporate bonds.
[4]	Internal valuation model includes discounted cash flow models and the Black-Scholes option pricing model.
[5]	This input represents the counterparty default rate derived from the MHFG Group's own internal credit analyses.

Fair Value (Summary of Asset110

Fair Value (Summary of Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis) (Detail) - Fair Value, Measurements, Nonrecurring - JPY (¥) ¥ in Billions	Sep. 30, 2017	Mar. 31, 2017
Assets:
Loans	¥ 120	¥ 124
Loans held-for-sale	5	7
Other investments		7
Premises and equipment-net		7
Total assets measured at fair value	125	145
Aggregate cost
Assets:
Loans	183	194
Loans held-for-sale	8	8
Other investments	1	11
Premises and equipment-net		11
Total assets measured at fair value	192	224
Level 1
Assets:
Other investments		6
Total assets measured at fair value		6
Level 2
Assets:
Loans held-for-sale	5	7
Premises and equipment-net		6
Total assets measured at fair value	5	13
Level 3
Assets:
Loans	120	124
Other investments		1
Premises and equipment-net		1
Total assets measured at fair value	¥ 120	¥ 126

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, 2017	Mar. 31, 2017
Financial liabilities:
Long-term debt		¥ 1,943,986	¥ 1,496,488
Carrying amount
Financial assets:
Cash and due from banks, call loans and funds sold, and receivables under resale agreements and securities borrowing transactions		65,291,000	60,943,000
Investments		3,127,000	3,817,000
Loans, net of allowance for loan losses	[1]	83,401,000	81,662,000
Financial liabilities:
Noninterest-bearing deposits, call money and funds purchased, and payables under repurchase agreements and securities lending transactions		46,373,000	42,205,000
Interest-bearing deposits		114,675,000	110,125,000
Due to trust accounts		3,999,000	4,123,000
Other short-term borrowings		931,000	1,477,000
Long-term debt		12,157,000	13,009,000
Estimated fair value
Financial assets:
Cash and due from banks, call loans and funds sold, and receivables under resale agreements and securities borrowing transactions		65,291,000	60,943,000
Investments		3,148,000	3,846,000
Loans, net of allowance for loan losses	[1]	84,306,000	82,696,000
Financial liabilities:
Noninterest-bearing deposits, call money and funds purchased, and payables under repurchase agreements and securities lending transactions		46,373,000	42,205,000
Interest-bearing deposits		114,668,000	110,124,000
Due to trust accounts		3,999,000	4,123,000
Other short-term borrowings		931,000	1,477,000
Long-term debt		12,258,000	13,078,000
Estimated fair value | Level 1
Financial assets:
Cash and due from banks, call loans and funds sold, and receivables under resale agreements and securities borrowing transactions		909,000	1,063,000
Investments		3,148,000	3,846,000
Financial liabilities:
Noninterest-bearing deposits, call money and funds purchased, and payables under repurchase agreements and securities lending transactions		21,957,000	20,544,000
Interest-bearing deposits		57,802,000	56,738,000
Estimated fair value | Level 2
Financial assets:
Cash and due from banks, call loans and funds sold, and receivables under resale agreements and securities borrowing transactions		64,382,000	59,880,000
Financial liabilities:
Noninterest-bearing deposits, call money and funds purchased, and payables under repurchase agreements and securities lending transactions		24,416,000	21,661,000
Interest-bearing deposits		56,866,000	53,386,000
Due to trust accounts		3,999,000	4,123,000
Other short-term borrowings		931,000	1,477,000
Long-term debt		11,274,000	12,120,000
Estimated fair value | Level 3
Financial assets:
Loans, net of allowance for loan losses	[1]	84,306,000	82,696,000
Financial liabilities:
Long-term debt		¥ 984,000	¥ 958,000
[1]	Loans, net of allowance for loan losses include items measured at fair value on a nonrecurring basis.

Offsetting of Financial Asse112

Offsetting of Financial Assets and Financial Liabilities (Information of Offsetting of Financial Assets and Financial Liabilities) (Detail) - JPY (¥) ¥ in Billions		Sep. 30, 2017	Mar. 31, 2017
Offsetting Financial Assets And Financial Liabilities [Line Items]
Derivative assets, Gross amounts recognized	[1]	¥ 9,806	¥ 10,608
Derivative assets, Gross amounts offset on the balance sheet	[1]	0	0
Derivative assets, Net amounts presented on the balance sheet	[1],[2]	9,806	10,608
Derivative assets, Amounts not offset on the balance sheet, Financial instruments	[1],[3],[4]	(8,370)	(8,966)
Derivative assets, Amounts not offset on the balance sheet, Cash collateral	[1],[3]	(504)	(620)
Derivative assets, Net amounts	[1]	932	1,022
Receivables under resale agreements, Gross amounts recognized	[1]	9,162	8,698
Receivables under resale agreements, Gross amounts offset on the balance sheet	[1]	0	0
Receivables under resale agreements, Net amounts presented on the balance sheet	[1],[2]	9,162	8,698
Receivables under resale agreements, Amounts not offset on the balance sheet, Financial instruments	[1],[3],[4]	(9,105)	(8,662)
Receivables under resale agreements, Amounts not offset on the balance sheet, Cash collateral	[1],[3]	0	0
Receivables under resale agreements, Net amounts	[1]	57	36
Receivables under securities borrowing transactions, Gross amounts recognized	[1]	3,192	3,127
Receivables under securities borrowing transactions, Gross amounts offset on the balance sheet	[1]	0	0
Receivables under securities borrowing transactions, Net amounts presented on the balance sheet	[1],[2]	3,192	3,127
Receivables under securities borrowing transactions, Amounts not offset on the balance sheet, Financial instruments	[1],[3],[4]	(3,172)	(3,116)
Receivables under securities borrowing transactions, Amounts not offset on the balance sheet, Cash collateral	[1],[3]	0	0
Receivables under securities borrowing transactions, Net amounts	[1]	20	11
Financial assets, Gross amounts recognized, Total	[1]	22,160	22,433
Financial assets, Gross amounts offset on the balance sheet, Total	[1]	0	0
Financial assets, Net amounts presented on the balance sheet, Total	[1],[2]	22,160	22,433
Financial assets, Amounts not offset on the balance sheet, Financial instruments, Total	[1],[3],[4]	(20,647)	(20,744)
Financial assets, Amounts not offset on the balance sheet, Cash collateral, Total	[1],[3]	(504)	(620)
Financial assets, Net amounts, Total	[1]	1,009	1,069
Derivative liabilities, Gross amounts recognized	[1]	9,658	10,405
Derivative liabilities, Gross amounts offset on the balance sheet	[1]	0	0
Derivative liabilities, Net amounts presented on the balance sheet	[1],[2]	9,658	10,405
Derivative liabilities, Amounts not offset on the balance sheet, Financial instruments	[1],[3],[4]	(8,120)	(8,866)
Derivative liabilities, Amounts not offset on the balance sheet, Cash collateral	[1],[3]	(972)	(901)
Derivative liabilities, Net amounts	[1]	566	638
Payables under repurchase agreements, Gross amounts recognized	[1]	18,453	17,446
Payables under repurchase agreements, Gross amounts offset on the balance sheet	[1]	0	0
Payables under repurchase agreements, Net amounts presented on the balance sheet	[1],[2]	18,453	17,446
Payables under repurchase agreements, Amounts not offset on the balance sheet, Financial instruments	[1],[3],[4]	(18,275)	(17,391)
Payables under repurchase agreements, Amounts not offset on the balance sheet, Cash collateral	[1],[3]	0	0
Payables under repurchase agreements, Net amounts	[1]	178	55
Payables under securities lending transactions, Gross amounts recognized	[1]	2,315	1,458
Payables under securities lending transactions, Gross amounts offset on the balance sheet	[1]	0	0
Payables under securities lending transactions, Net amounts presented on the balance sheet	[1],[2]	2,315	1,458
Payables under securities lending transactions, Amounts not offset on the balance sheet, Financial instruments	[1],[3],[4]	(2,277)	(1,455)
Payables under securities lending transactions, Amounts not offset on the balance sheet, Cash collateral	[1],[3]	0	0
Payables under securities lending transactions, Net amounts	[1]	38	3
Financial liabilities, Gross amounts recognized, Total	[1]	30,426	29,309
Financial liabilities, Gross amounts offset on the balance sheet, Total	[1]	0	0
Financial liabilities, Net amounts presented on the balance sheet, Total	[1],[2]	30,426	29,309
Financial liabilities, Amounts not offset on the balance sheet, Financial instruments, Total	[1],[3],[4]	(28,672)	(27,712)
Financial liabilities, Amounts not offset on the balance sheet, Cash collateral, Total	[1],[3]	(972)	(901)
Financial liabilities, Net amounts, Total	[1]	¥ 782	¥ 696
[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.

Repurchase Agreements and Se113

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, 2017	Mar. 31, 2017
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements	[1]	¥ 19,522	¥ 17,970
Securities lending transactions	[1]	2,873	1,919
Total		22,395	19,889
Overnight and continuous
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		534	249
Securities lending transactions		2,177	320
Total		2,711	569
Up to 30 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		13,199	12,700
Securities lending transactions		463	1,359
Total		13,662	14,059
31 to 90 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		4,596	3,897
Total		4,596	3,897
Greater than 90 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		1,193	1,124
Securities lending transactions		233	240
Total		¥ 1,426	¥ 1,364
[1]	Amounts exceeded the gross amounts recognized in Note 20 "Offsetting of financial assets and financial liabilities" by ¥985 billion and ¥1,627 billion, at March 31, 2017 and September 30, 2017, 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 Se114

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, 2017	Mar. 31, 2017
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements	[1]	¥ 19,522	¥ 17,970
Securities lending transactions	[1]	2,873	1,919
Japanese government bonds and Japanese local government bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		1,156	1,127
Securities lending transactions		1,767	1,152
Foreign government bonds and foreign agency mortgage-backed securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		17,332	15,782
Securities lending transactions		453	375
Commercial Paper and Corporate Bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		377	294
Securities lending transactions		47	47
Equity Securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		514	578
Securities lending transactions		583	320
Other securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		143	189
Securities lending transactions		¥ 23	¥ 25
[1]	Amounts exceeded the gross amounts recognized in Note 20 "Offsetting of financial assets and financial liabilities" by ¥985 billion and ¥1,627 billion, at March 31, 2017 and September 30, 2017, 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 Se115

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, 2017	Mar. 31, 2017
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	¥ 1,627	¥ 985

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, 2017	Sep. 30, 2016
Japan Gaap Schedule of Segment Reporting Information, by Segment [Line Items]
Gross profits		¥ 959.8	¥ 1,089.7
General and administrative expenses		718.3	680.5
Equity in earnings (losses) of equity method investees-net		10.6	11.3
Others		(10.5)	(17.3)
Net business profits (losses)	[1]	241.6	403.2
Operating Segments [Member] | Retail And Business Banking Company
Japan Gaap Schedule of Segment Reporting Information, by Segment [Line Items]
Gross profits		343	348
General and administrative expenses		358.6	359.8
Equity in earnings (losses) of equity method investees-net		7.5	8.8
Net business profits (losses)	[1]	(8.1)	(3)
Operating Segments [Member] | Corporate And Institutional Company
Japan Gaap Schedule of Segment Reporting Information, by Segment [Line Items]
Gross profits		192	215.2
General and administrative expenses		97.3	96.5
Equity in earnings (losses) of equity method investees-net		0.6	0.6
Net business profits (losses)	[1]	95.3	119.3
Operating Segments [Member] | Global Corporate Company
Japan Gaap Schedule of Segment Reporting Information, by Segment [Line Items]
Gross profits		160.2	183.4
General and administrative expenses		122.5	117.9
Equity in earnings (losses) of equity method investees-net		1.4	1
Net business profits (losses)	[1]	39.1	66.5
Operating Segments [Member] | Global Markets Company
Japan Gaap Schedule of Segment Reporting Information, by Segment [Line Items]
Gross profits		236.2	333.6
General and administrative expenses		99.7	90.1
Net business profits (losses)	[1]	136.5	243.5
Operating Segments [Member] | Asset management company.
Japan Gaap Schedule of Segment Reporting Information, by Segment [Line Items]
Gross profits		24.9	24.4
General and administrative expenses		13.9	15
Equity in earnings (losses) of equity method investees-net		0.3	(0.1)
Net business profits (losses)	[1]	11.3	9.3
Others
Japan Gaap Schedule of Segment Reporting Information, by Segment [Line Items]
Gross profits	[2]	3.5	(14.9)	[3]
General and administrative expenses	[2]	26.3	1.2	[3]
Equity in earnings (losses) of equity method investees-net	[2]	0.8	1	[3]
Others	[2]	(10.5)	(17.3)	[3]
Net business profits (losses)	[1],[2]	¥ (32.5)	¥ (32.4)	[3]
[1]	Net business profits is used in Japan as a measure of the profitability of core banking operations, and is defined as gross profits (or the sum of net interest income, fiduciary income, net fee and commission income, net trading income and net other operating income) less general and administrative expenses. Measurement of net business profits is required for regulatory reporting to the Financial Services Agency.
[2]	"Others" includes items which should be eliminated as internal transactions between each segment on a consolidated basis.
[3]	Beginning on April 1, 2017, new allocation methods for transactions between each segment and "Others" have been applied. Figures for the six months ended September 30, 2016 have been restated for the new allocation methods and "Equity in earnings (losses) of equity method investees-net" has been presented as a new item in connection with the use of the new allocation methods.

Business Segment Information117

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, 2017	Sep. 30, 2016
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Net business profits	¥ 241,600	¥ 403,200
U.S. GAAP adjustments	95,700	14,800
(Provision) credit for loan losses	117,962	(569)
Net gains (losses) related to equity investments	100,900	64,500
Non-recurring personnel expense	(3,600)	(4,700)
Gains on disposal of premises and equipment	4,567	3,486
(Provision) credit for losses on off-balance-sheet instruments	4,191	7,895
Others-net	(48,500)	(31,300)
Income before income tax expense	¥ 512,863	¥ 457,273