Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock Voting	Additional Paid In Capital	Accumulated Other Comprehensive Income (Loss)	Treasury Stock	Retained Earnings
Beginning balance, common stock (in shares) at Mar. 31, 2022		126,425,383
Beginning balance at Mar. 31, 2022	$ 2,060,395	$ 126	$ 3,023,403	$ 141	$ (1,373,840)	$ 410,565
Beginning balance, treasury stock (in shares) at Mar. 31, 2022					52,323,090
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	10,251					10,251
Unrealized net investment gains (losses)	(11)			(11)
Unrealized net loss on derivative financial instruments	(625)			(625)
Cumulative translation adjustments	(561)			(561)
Issuance of common stock pursuant to vesting of restricted stock units (in shares)		1,741,744
Issuance of common stock pursuant to vesting of restricted stock units	2	$ 2
Stock-based compensation expense for restricted stock units granted to employees	30,702		30,702
Issuance of common stock under employee stock purchase plan (in shares)		206,029
Issuance of common stock under employee stock purchase plan	6,539		6,539
Repurchase of treasury stock (in shares)					3,806,416
Repurchase of treasury stock	(169,046)		(45,000)		$ (124,046)
Ending balance, common stock (in shares) at Sep. 30, 2022		128,373,156
Ending balance at Sep. 30, 2022	1,937,646	$ 128	3,015,644	(1,056)	$ (1,497,886)	420,816
Ending balance, treasury stock (in shares) at Sep. 30, 2022					56,129,506
Beginning balance, common stock (in shares) at Mar. 31, 2022		126,425,383
Beginning balance at Mar. 31, 2022	$ 2,060,395	$ 126	3,023,403	141	$ (1,373,840)	410,565
Beginning balance, treasury stock (in shares) at Mar. 31, 2022					52,323,090
Ending balance, common stock (in shares) at Mar. 31, 2023	71,249,045	128,683,824
Ending balance at Mar. 31, 2023	$ 2,029,649	$ 128	3,099,698	5,738	$ (1,546,128)	470,213
Ending balance, treasury stock (in shares) at Mar. 31, 2023	57,434,779				57,434,779
Beginning balance, common stock (in shares) at Jun. 30, 2022		127,371,813
Beginning balance at Jun. 30, 2022	$ 1,906,889	$ 127	2,993,163	(147)	$ (1,489,687)	403,433
Beginning balance, treasury stock (in shares) at Jun. 30, 2022					55,887,992
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	17,383					17,383
Unrealized net investment gains (losses)	0
Unrealized net loss on derivative financial instruments	(599)			(599)
Cumulative translation adjustments	(310)			(310)
Issuance of common stock pursuant to vesting of restricted stock units (in shares)		795,314
Issuance of common stock pursuant to vesting of restricted stock units	1	$ 1
Stock-based compensation expense for restricted stock units granted to employees	15,942		15,942
Issuance of common stock under employee stock purchase plan (in shares)		206,029
Issuance of common stock under employee stock purchase plan	6,539		6,539
Repurchase of treasury stock (in shares)					241,514
Repurchase of treasury stock	(8,199)		0		$ (8,199)
Ending balance, common stock (in shares) at Sep. 30, 2022		128,373,156
Ending balance at Sep. 30, 2022	$ 1,937,646	$ 128	3,015,644	(1,056)	$ (1,497,886)	420,816
Ending balance, treasury stock (in shares) at Sep. 30, 2022					56,129,506
Beginning balance, common stock (in shares) at Mar. 31, 2023	71,249,045	128,683,824
Beginning balance at Mar. 31, 2023	$ 2,029,649	$ 128	3,099,698	5,738	$ (1,546,128)	470,213
Beginning balance, treasury stock (in shares) at Mar. 31, 2023	57,434,779				57,434,779
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 17,262					17,262
Unrealized net investment gains (losses)	(97)			(97)
Unrealized net loss on derivative financial instruments	(192)			(192)
Cumulative translation adjustments	(70)			(70)
Issuance of common stock pursuant to vesting of restricted stock units (in shares)		1,981,783
Issuance of common stock pursuant to vesting of restricted stock units		$ 2
Stock-based compensation expense for restricted stock units granted to employees	37,008		37,008
Issuance of common stock under employee stock purchase plan (in shares)		209,791
Issuance of common stock under employee stock purchase plan	6,006		6,006
Repurchase of treasury stock (in shares)					1,742,718
Repurchase of treasury stock	$ (49,898)		0		$ (49,898)
Ending balance, common stock (in shares) at Sep. 30, 2023	71,697,901	130,875,398
Ending balance at Sep. 30, 2023	$ 2,039,670	$ 130	3,142,712	5,379	$ (1,596,026)	487,475
Ending balance, treasury stock (in shares) at Sep. 30, 2023	59,177,497				59,177,497
Beginning balance, common stock (in shares) at Jun. 30, 2023		130,016,041
Beginning balance at Jun. 30, 2023	$ 2,031,210	$ 130	3,118,798	5,803	$ (1,559,534)	466,013
Beginning balance, treasury stock (in shares) at Jun. 30, 2023					57,869,951
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	21,462					21,462
Unrealized net investment gains (losses)	9			9
Unrealized net loss on derivative financial instruments	(295)			(295)
Cumulative translation adjustments	(138)			(138)
Issuance of common stock pursuant to vesting of restricted stock units (in shares)		649,566
Stock-based compensation expense for restricted stock units granted to employees	17,908		17,908
Issuance of common stock under employee stock purchase plan (in shares)		209,791
Issuance of common stock under employee stock purchase plan	6,006		6,006
Repurchase of treasury stock (in shares)					1,307,546
Repurchase of treasury stock	$ (36,492)		0		$ (36,492)
Ending balance, common stock (in shares) at Sep. 30, 2023	71,697,901	130,875,398
Ending balance at Sep. 30, 2023	$ 2,039,670	$ 130	$ 3,142,712	$ 5,379	$ (1,596,026)	$ 487,475
Ending balance, treasury stock (in shares) at Sep. 30, 2023	59,177,497				59,177,497