CONDENSED CONSOLIDATED STATEMENTS OF EQUITY (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Treasury Stock	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Beginning balance (in shares) at Mar. 31, 2020		135,927		(22,421)
Beginning balance at Mar. 31, 2020	$ 2,539,244	$ 1,359	$ 2,134,748	$ (820,572)	$ 1,282,085	$ (58,376)
Increase (Decrease) in Stockholders' Equity
Net income	370,074				370,074
Change in cumulative foreign currency translation adjustment	53,697					53,697
Change in gains on cash flow hedge, net	(4,905)					(4,905)
Net unrealized gain on available-for-sale securities, net of taxes	4,000					4,000
Stock-based compensation	141,904		141,904
Issuance of restricted stock, net of forfeitures and cancellations (in shares)		1,235
Issuance of restricted stock, net of forfeitures and cancellations	1	$ 13	(12)
Net share settlement of restricted stock awards (in shares)		(401)
Net share settlement of restricted stock awards	(60,586)	$ (5)	(60,581)
Employee share purchase plan settlement (in shares)		139
Employee share purchase plan settlement	14,215	$ 2	14,213
Issuance of shares related to acquisition (in shares)		604
Issuance of shares related to acquisition	97,647	$ 6	97,641
Ending balance (in shares) at Dec. 31, 2020		137,504		(22,421)
Ending balance at Dec. 31, 2020	3,155,291	$ 1,375	2,327,913	$ (820,572)	1,652,159	(5,584)
Beginning balance (in shares) at Sep. 30, 2020		137,349		(22,421)
Beginning balance at Sep. 30, 2020	2,901,282	$ 1,373	2,285,394	$ (820,572)	1,469,911	(34,824)
Increase (Decrease) in Stockholders' Equity
Net income	182,248				182,248
Change in cumulative foreign currency translation adjustment	30,135					30,135
Change in gains on cash flow hedge, net	(600)					(600)
Net unrealized gain on available-for-sale securities, net of taxes	(295)					(295)
Stock-based compensation	47,192		47,192
Issuance of restricted stock, net of forfeitures and cancellations (in shares)		141
Issuance of restricted stock, net of forfeitures and cancellations	1	$ 2	(1)
Net share settlement of restricted stock awards (in shares)		(60)
Net share settlement of restricted stock awards	(12,384)	$ (1)	(12,383)
Employee share purchase plan settlement (in shares)		74
Employee share purchase plan settlement	7,712	$ 1	7,711
Ending balance (in shares) at Dec. 31, 2020		137,504		(22,421)
Ending balance at Dec. 31, 2020	3,155,291	$ 1,375	2,327,913	$ (820,572)	1,652,159	(5,584)
Beginning balance (in shares) at Mar. 31, 2021		137,584		(22,421)
Beginning balance at Mar. 31, 2021	3,331,892	$ 1,376	2,288,781	$ (820,572)	1,870,971	(8,664)
Increase (Decrease) in Stockholders' Equity
Net income	307,050				307,050
Change in cumulative foreign currency translation adjustment	(24,096)					(24,096)
Net unrealized gain on available-for-sale securities, net of taxes	(1,823)					(1,823)
Stock-based compensation	198,045		198,045
Repurchased common stock (in shares)				(1,260)
Repurchased common stock	(200,012)			$ (200,012)
Issuance of restricted stock, net of forfeitures and cancellations (in shares)		1,096
Issuance of restricted stock, net of forfeitures and cancellations	0	$ 11	(11)
Net share settlement of restricted stock awards (in shares)		(330)
Net share settlement of restricted stock awards	(59,131)	$ (3)	(59,128)
Employee share purchase plan settlement (in shares)		142
Employee share purchase plan settlement	19,658	$ 2	19,656
Issuance of shares related to acquisition (in shares)		515
Issuance of shares related to acquisition	94,154	$ 5	94,149
Ending balance (in shares) at Dec. 31, 2021		139,007		(23,681)
Ending balance at Dec. 31, 2021	3,665,737	$ 1,391	2,541,492	$ (1,020,584)	2,178,021	(34,583)
Beginning balance (in shares) at Sep. 30, 2021		138,891		(23,681)
Beginning balance at Sep. 30, 2021	3,469,668	$ 1,390	2,475,085	$ (1,020,584)	2,033,524	(19,747)
Increase (Decrease) in Stockholders' Equity
Net income	144,497				144,497
Change in cumulative foreign currency translation adjustment	(13,497)					(13,497)
Net unrealized gain on available-for-sale securities, net of taxes	(1,339)					(1,339)
Stock-based compensation	61,741		61,741
Issuance of restricted stock, net of forfeitures and cancellations (in shares)		76
Issuance of restricted stock, net of forfeitures and cancellations	0	$ 1	(1)
Net share settlement of restricted stock awards (in shares)		(32)
Net share settlement of restricted stock awards	(5,761)	$ (1)	(5,760)
Employee share purchase plan settlement (in shares)		72
Employee share purchase plan settlement	10,428	$ 1	10,427
Ending balance (in shares) at Dec. 31, 2021		139,007		(23,681)
Ending balance at Dec. 31, 2021	$ 3,665,737	$ 1,391	$ 2,541,492	$ (1,020,584)	$ 2,178,021	$ (34,583)