Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock Voting	Additional Paid In Capital	Accumulated Other Comprehensive Loss	Treasury Stock	Retained Earnings
Beginning balance (in shares) at Mar. 31, 2020		122,006,077			(49,785,171)
Beginning balance at Mar. 31, 2020	$ 1,937,919	$ 122	$ 2,891,553	$ (3,160)	$ (1,305,935)	$ 355,339
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	7,915					7,915
Unrealized net investment losses	(122)			(122)
Unrealized net gains on derivative financial instruments	169			169
Cumulative translation adjustments	3,375			3,375
Issuance of common stock pursuant to vesting of restricted stock units (in shares)		1,581,484
Issuance of common stock pursuant to vesting of restricted stock units	2	$ 2
Stock-based compensation expense for restricted stock units granted to employees	38,545		38,545
Issuance of common stock under employee stock purchase plan (in shares)		279,812
Issuance of common stock under employee stock purchase plan	6,475		6,475
Repurchase of treasury stock (in shares)					(644,178)
Repurchase of treasury stock	(16,043)				$ (16,043)
Ending balance (in shares) at Dec. 31, 2020		123,867,373			(50,429,349)
Ending balance at Dec. 31, 2020	1,978,235	$ 124	2,936,573	262	$ (1,321,978)	363,254
Beginning balance (in shares) at Sep. 30, 2020		123,840,945			(50,266,910)
Beginning balance at Sep. 30, 2020	1,939,320	$ 123	2,924,757	(1,258)	$ (1,318,535)	334,233
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	29,021					29,021
Unrealized net investment losses	(15)			(15)
Unrealized net gains on derivative financial instruments	53			53
Cumulative translation adjustments	1,482			1,482
Issuance of common stock pursuant to vesting of restricted stock units (in shares)		26,428
Issuance of common stock pursuant to vesting of restricted stock units	1	$ 1
Stock-based compensation expense for restricted stock units granted to employees	11,816		11,816
Repurchase of treasury stock (in shares)					(162,439)
Repurchase of treasury stock	(3,443)				$ (3,443)
Ending balance (in shares) at Dec. 31, 2020		123,867,373			(50,429,349)
Ending balance at Dec. 31, 2020	1,978,235	$ 124	2,936,573	262	$ (1,321,978)	363,254
Beginning balance (in shares) at Mar. 31, 2021		124,197,974			(50,446,359)
Beginning balance at Mar. 31, 2021	2,005,779	$ 124	2,955,400	(1,940)	$ (1,322,496)	374,691
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	44,280					44,280
Unrealized net investment losses	(5)			(5)
Unrealized net gains on derivative financial instruments	99			99
Cumulative translation adjustments	51			51
Issuance of common stock pursuant to vesting of restricted stock units (in shares)		1,688,026
Issuance of common stock pursuant to vesting of restricted stock units	2	$ 2
Stock-based compensation expense for restricted stock units granted to employees	41,389		41,389
Issuance of common stock under employee stock purchase plan (in shares)		251,308
Issuance of common stock under employee stock purchase plan	6,890		6,890
Repurchase of treasury stock (in shares)					(1,862,403)
Repurchase of treasury stock	(50,898)				$ (50,898)
Ending balance (in shares) at Dec. 31, 2021		126,137,308			(52,308,762)
Ending balance at Dec. 31, 2021	2,047,587	$ 126	3,003,679	(1,795)	$ (1,373,394)	418,971
Beginning balance (in shares) at Sep. 30, 2021		126,108,858			(51,891,197)
Beginning balance at Sep. 30, 2021	1,999,004	$ 126	2,991,704	(1,931)	$ (1,362,141)	371,246
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	47,725					47,725
Unrealized net investment losses	0
Unrealized net gains on derivative financial instruments	52			52
Cumulative translation adjustments	84			84
Issuance of common stock pursuant to vesting of restricted stock units (in shares)		28,450
Issuance of common stock pursuant to vesting of restricted stock units	0	$ 0
Stock-based compensation expense for restricted stock units granted to employees	11,975		11,975
Repurchase of treasury stock (in shares)					(417,565)
Repurchase of treasury stock	(11,253)				$ (11,253)
Ending balance (in shares) at Dec. 31, 2021		126,137,308			(52,308,762)
Ending balance at Dec. 31, 2021	$ 2,047,587	$ 126	$ 3,003,679	$ (1,795)	$ (1,373,394)	$ 418,971