Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Treasury Stock	Additional Paid in Capital	Retained Earnings (Accumulated Deficit)	Accumulated Other Comprehensive Income (Loss)
Beginning Balance at Mar. 31, 2017	$ 452,071	$ 437	$ (46,763)	$ 565,962	$ (46,959)	$ (20,606)
Beginning Balance (in shares) at Mar. 31, 2017		43,673,286	1,575,995
Cumulative effect of adoption of new accounting standard	77,081			1,835	75,246
Restricted stock units issued		$ 4		(4)
Restricted stock units issued (in shares)		371,940
Stock options exercised	9,303	$ 5		9,298
Stock options exercised (in shares)		459,777
Stock issued under employee stock purchase plan	2,394			2,394
Stock issued under employee stock purchase plan (in shares)		19,286
Stock issued to directors	67			67
Stock issued to directors (in shares)		365
Return of common stock to pay withholding taxes on restricted stock	(20,317)	$ (2)	$ (20,315)
Return of common stock to pay withholding taxes on restricted stock (in shares)		(149,317)	149,317
Stock compensation expense	40,353			40,353
Other comprehensive income (loss)	16,402					16,402
Net income	112,170				112,170
Ending Balance at Mar. 31, 2018	689,524	$ 444	$ (67,078)	619,905	140,457	(4,204)
Ending Balance (in shares) at Mar. 31, 2018		44,375,337	1,725,312
Restricted stock units issued		$ 4		(4)
Restricted stock units issued (in shares)		427,431
Stock options exercised	12,949	$ 5		12,944
Stock options exercised (in shares)		485,363
Stock issued under employee stock purchase plan	3,052			3,052
Stock issued under employee stock purchase plan (in shares)		12,467
Stock issued to directors	116			116
Stock issued to directors (in shares)		316
Return of common stock to pay withholding taxes on restricted stock	(71,776)	$ (2)	$ (71,774)
Return of common stock to pay withholding taxes on restricted stock (in shares)		(177,929)	177,929
Stock compensation expense	54,494			54,494
Other comprehensive income (loss)	(10,485)					(10,485)
Net income	259,016				259,016
Ending Balance at Mar. 31, 2019	$ 936,890	$ 451	$ (138,852)	690,507	399,473	(14,689)
Ending Balance (in shares) at Mar. 31, 2019	45,122,985	45,122,985	1,903,241
Restricted stock units issued		$ 4		(4)
Restricted stock units issued (in shares)		392,872
Stock options exercised	$ 3,748	$ 2		3,747
Stock options exercised (in shares)	85,000	85,136
Stock issued under employee stock purchase plan	$ 5,103			5,103
Stock issued under employee stock purchase plan (in shares)		37,827
Return of common stock to pay withholding taxes on restricted stock	(41,687)	$ (2)	$ (41,685)
Return of common stock to pay withholding taxes on restricted stock (in shares)		(164,446)	164,446
Stock compensation expense	39,781			39,781
Stock repurchase program	$ (84,879)	$ (5)	$ (84,874)
Stock Repurchased During Period, Shares	(465,687)	465,687	(465,687)
Other comprehensive income (loss)	$ 3,500					3,500
Net income	203,009				203,009
Ending Balance at Mar. 31, 2020	$ 1,065,466	$ 451	$ (265,411)	$ 739,133	$ 602,482	$ (11,189)
Ending Balance (in shares) at Mar. 31, 2020	45,008,687	45,008,687	2,533,374