Net Income Per Share - Computations of Basic and Diluted Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Earnings Per Share [Abstract]
Net income	$ 139,456	$ 266,914	$ 326,297	$ 338,987
Shares used in net income per share computation:
Weighted average shares outstanding - basic (in shares)	168,389	168,645	168,380	168,140
Effect of potentially dilutive equivalent shares (in shares)	2,954	2,737	3,302	2,626
Weighted average shares outstanding - diluted (in shares)	171,343	171,382	171,682	170,766
Net income per share:
Basic (in dollars per share)	$ 0.83	$ 1.58	$ 1.94	$ 2.02
Diluted (in dollars per share)	$ 0.81	$ 1.56	$ 1.90	$ 1.99
Anti-dilutive equivalents shares excluded (in shares)	500	400	500	400