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, 2015	$ 291,560	$ 413	$ (19,347)	$ 465,046	$ (137,222)	$ (17,330)
Beginning Balance (in shares) at Mar. 31, 2015		41,335,773	1,282,944
Restricted stock units issued		$ 5		(5)
Restricted stock units issued (in shares)		507,471
Stock options exercised	9,771	$ 8		9,763
Stock options exercised (in shares)		829,385
Stock issued under employee stock purchase plan	1,135			1,135
Stock issued under employee stock purchase plan (in shares)		16,772
Stock issued to directors	65			65
Stock issued to directors (in shares)		774
Return of common stock to pay withholding taxes on restricted stock	(7,313)		$ (7,313)
Return of common stock to pay withholding taxes on restricted stock (in shares)		(93,947)	93,947
Stock compensation expense	29,053			29,053
Excess tax benefit from stock-based awards	3,567			3,567
Other comprehensive income (loss)	2,790					2,790
Net income	38,147				38,147
Ending Balance at Mar. 31, 2016	368,775	$ 426	$ (26,660)	508,624	(99,075)	(14,540)
Ending Balance (in shares) at Mar. 31, 2016		42,596,228	1,376,891
Restricted stock units issued		$ 5		(5)
Restricted stock units issued (in shares)		502,417
Stock options exercised	10,660	$ 8		10,652
Stock options exercised (in shares)		754,893
Stock issued under employee stock purchase plan	1,720			1,720
Stock issued under employee stock purchase plan (in shares)		18,288
Stock issued to directors	67			67
Stock issued to directors (in shares)		564
Return of common stock to pay withholding taxes on restricted stock	(20,105)	$ (2)	$ (20,103)
Return of common stock to pay withholding taxes on restricted stock (in shares)		(199,104)	199,104
Stock compensation expense	32,866			32,866
Excess tax benefit from stock-based awards	12,038			12,038
Other comprehensive income (loss)	(6,066)					(6,066)
Net income	52,116				52,116
Ending Balance at Mar. 31, 2017	$ 452,071	$ 437	$ (46,763)	565,962	(46,959)	(20,606)
Ending Balance (in shares) at Mar. 31, 2017	43,673,286	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)	460,000	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	44,375,337	1,725,312