CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Cumulative adjustment from adoption of recent accounting pronouncements	Common Stock	Additional Paid-in Capital	Retained Earnings	Retained Earnings Cumulative adjustment from adoption of recent accounting pronouncements	Accumulated Other Comprehensive Loss
Beginning balance (in shares) at Mar. 31, 2018			30,447,000
Beginning balance at Mar. 31, 2018	$ 940,779	$ 468	$ 304	$ 167,587	$ 785,871	$ 468	$ (12,983)
Increase (Decrease) in Stockholders' Equity
Stock-based compensation expense (in shares)			10,000
Stock-based compensation expense	14,773			14,773
Shares issued upon vesting (in shares)			85,000
Shares issued upon vesting	1,025		$ 1	1,024
Shares withheld for taxes	$ (5,157)			(5,157)
Repurchases of common stock (in shares)	(1,400,699)		(1,401,000)
Repurchases of common stock	$ (161,395)		$ (14)		(161,381)
Net income	264,308				264,308
Total other comprehensive income (loss)	(9,671)						(9,671)
Ending balance (in shares) at Mar. 31, 2019			29,141,000
Ending balance at Mar. 31, 2019	1,045,130	$ (1,068)	$ 291	178,227	889,266	$ (1,068)	(22,654)
Increase (Decrease) in Stockholders' Equity
Stock-based compensation expense (in shares)			10,000
Stock-based compensation expense	14,471			14,471
Shares issued upon vesting (in shares)			86,000
Shares issued upon vesting	1,288		$ 1	1,287
Exercise of stock options (in shares)			58,000
Exercise of stock options	3,615		$ 1	3,614
Shares withheld for taxes	$ (6,148)			(6,148)
Repurchases of common stock (in shares)	(1,296,201)		(1,296,000)
Repurchases of common stock	$ (190,405)		$ (13)		(190,392)
Net income	276,142				276,142
Total other comprehensive income (loss)	(2,905)						(2,905)
Ending balance (in shares) at Mar. 31, 2020			27,999,000
Ending balance at Mar. 31, 2020	1,140,120		$ 280	191,451	973,948		(25,559)
Increase (Decrease) in Stockholders' Equity
Stock-based compensation expense (in shares)			4,000
Stock-based compensation expense	22,695			22,695
Shares issued upon vesting (in shares)			107,000
Shares issued upon vesting	1,502		$ 1	1,501
Exercise of stock options (in shares)			107,000
Exercise of stock options	6,775		$ 1	6,774
Shares withheld for taxes	$ (19,111)			(19,111)
Repurchases of common stock (in shares)	(307,080)		(307,000)
Repurchases of common stock	$ (99,147)		$ (3)		(99,144)
Net income	382,575				382,575
Total other comprehensive income (loss)	8,816						8,816
Ending balance (in shares) at Mar. 31, 2021			27,910,000
Ending balance at Mar. 31, 2021	$ 1,444,225		$ 279	$ 203,310	$ 1,257,379		$ (16,743)