Stock-based compensation (Tables)

12 Months Ended

Mar. 31, 2020

Share-based Payment Arrangement [Abstract]

Summary of Stock-Based Compensation Plan

The following is a roll-forward of MHFG Stock Plan for the fiscal year ended March 31, 2020:

	Number of shares		Weighted-average exercise price		Weighted-average remaining contractual term		Aggregate intrinsic value
			(in yen)		(in years)		(in millions of yen)
Outstanding at beginning of fiscal year		4,245,000		1
Exercised during fiscal year		2,968,000		1
Outstanding at end of fiscal year		1,277,000		1		13.91		157
Exercisable at end of fiscal year		—		—		—		—

Activities Related to Stock Compensation Program

The following table presents activities related to the stock compensation programs for the fiscal years ended March 31, 2019 and 2020:

	Stock Compensation I				Stock Compensation II
2019	Number of shares		Weighted-average grant-date fair value		Number of shares		Weighted-average grant-date fair value
			(per share in yen)				(per share in yen)
Nonvested at the beginning of the year		—		—		13,319,406		182.04
Granted during fiscal year		3,770,065		189.24		6,906,635		189.24
Vested during fiscal year		3,770,065		189.24		5,068,949		187.48
Forfeited during fiscal year		—		—		—		—
Nonvested at the end of the year		—		—		15,157,092		183.50
	Stock Compensation I				Stock Compensation II
2020	Number of shares		Weighted-average grant-date fair value		Number of shares		Weighted-average grant-date fair value
			(per share in yen)				(per share in yen)
Nonvested at the beginning of the year		—		—		15,157,092		183.50
Granted during fiscal year		5,748,997		159.59		3,281,003		159.59
Vested during fiscal year		5,748,997		159.59		7,014,809		182.07
Forfeited during fiscal year		—		—		—		—
Nonvested at the end of the year		—		—		11,423,286		177.51

Total Fair Value of Stock Compensation that Vested and Common Stock Acquired

The following table presents the total fair value of the stock compensation that vested and the total amount of the common stock acquired from the stock market by the trustee for the fiscal years ended March 31, 2019 and 2020:

	2019				2020
	Stock Compensation I		Stock Compensation II		Stock Compensation I		Stock Compensation II
	(in millions of yen)
Fair value of vested shares		713		930		917		1,090
Common stock shares acquired		713		1,307		917		524

Schedule Of Stock-Based Compensation Expense

The following table presents the compensation cost recognized in the stock compensation programs for the fiscal years ended March 31, 2018, 2019 and 2020:

	2018		2019		2020
	(in millions of yen)
Stock Compensation I		—		713		917
Stock Compensation II		868		1,287		1,247