CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Registered Shares	Additional Paid-in Capital	Treasury Shares	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Loss
Beginning of the period at Mar. 31, 2020	$ 1,489,268	$ (553)	$ 30,148	$ 75,097	$ (185,896)	$ 1,690,579	$ (553)	$ (120,660)
Beginning of the period (in shares) at Mar. 31, 2020			173,106		6,210
Increase (Decrease) in Shareholders' Equity
Total comprehensive income	340,795					338,987		1,808
Purchases of registered shares	(22,454)				$ (22,454)
Purchase of registered shares (in shares)					312
Sales of shares upon exercise of stock options and purchase rights	26,066			1,365	$ 24,701
Sales of shares upon exercise of stock options and purchase rights (in shares)					(1,211)
Issuance of shares upon vesting of restricted stock units	(25,744)			(43,135)	$ 17,391
Issuance of shares upon vesting of restricted stock units (in shares)					(954)
Share-based compensation	45,290			45,290
Cash dividends	(146,705)					(146,705)
End of the period at Sep. 30, 2020	1,705,963		$ 30,148	78,617	$ (166,258)	1,882,308		(118,852)
End of the period (in shares) at Sep. 30, 2020			173,106		4,357
Beginning of the period at Jun. 30, 2020	1,567,481		$ 30,148	54,668	$ (158,463)	1,762,099		(120,971)
Beginning of the period (in shares) at Jun. 30, 2020			173,106		4,689
Increase (Decrease) in Shareholders' Equity
Total comprehensive income	269,033					266,914		2,119
Purchases of registered shares	(22,454)				$ (22,454)
Purchase of registered shares (in shares)					312
Sales of shares upon exercise of stock options and purchase rights	16,074			3,255	$ 12,819
Sales of shares upon exercise of stock options and purchase rights (in shares)					(568)
Issuance of shares upon vesting of restricted stock units	(2,623)			(4,463)	$ 1,840
Issuance of shares upon vesting of restricted stock units (in shares)					(76)
Share-based compensation	25,157			25,157
Cash dividends	(146,705)					(146,705)
End of the period at Sep. 30, 2020	1,705,963		$ 30,148	78,617	$ (166,258)	1,882,308		(118,852)
End of the period (in shares) at Sep. 30, 2020			173,106		4,357
Beginning of the period at Mar. 31, 2021	2,261,789		$ 30,148	129,519	$ (279,541)	2,490,578		(108,915)
Beginning of the period (in shares) at Mar. 31, 2021			173,106		4,799
Increase (Decrease) in Shareholders' Equity
Total comprehensive income	324,193					326,297		(2,104)
Purchases of registered shares	(174,380)				$ (174,380)
Purchase of registered shares (in shares)					1,656
Sales of shares upon exercise of stock options and purchase rights	16,636			8,389	$ 8,247
Sales of shares upon exercise of stock options and purchase rights (in shares)					(226)
Issuance of shares upon vesting of restricted stock units	(54,751)			(87,080)	$ 32,329
Issuance of shares upon vesting of restricted stock units (in shares)					(898)
Share-based compensation	48,606			48,606
Cash dividends	(159,410)					(159,410)
End of the period at Sep. 30, 2021	2,262,683		$ 30,148	99,434	$ (413,345)	2,657,465		(111,019)
End of the period (in shares) at Sep. 30, 2021			173,106		5,331
Beginning of the period at Jun. 30, 2021	2,372,491		$ 30,148	74,948	$ (302,606)	2,677,419		(107,418)
Beginning of the period (in shares) at Jun. 30, 2021			173,106		4,407
Increase (Decrease) in Shareholders' Equity
Total comprehensive income	135,855					139,456		(3,601)
Purchases of registered shares	(119,508)				$ (119,508)
Purchase of registered shares (in shares)					1,151
Sales of shares upon exercise of stock options and purchase rights	13,886			8,168	$ 5,718
Sales of shares upon exercise of stock options and purchase rights (in shares)					(155)
Issuance of shares upon vesting of restricted stock units	(4,340)			(7,391)	$ 3,051
Issuance of shares upon vesting of restricted stock units (in shares)					(72)
Share-based compensation	23,709			23,709
Cash dividends	(159,410)					(159,410)
End of the period at Sep. 30, 2021	$ 2,262,683		$ 30,148	$ 99,434	$ (413,345)	$ 2,657,465		$ (111,019)
End of the period (in shares) at Sep. 30, 2021			173,106		5,331