CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income	Retained Earnings	Treasury Stock
Common stock, shares, beginning of period at Mar. 31, 2014		42,649
Stockholders' equity, beginning of period at Mar. 31, 2014	$ 698,664	$ 770	$ 663,483	$ 2,638	$ 123,389	$ (91,616)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	112,301				112,301
Foreign currency translation adjustments	476			476
Net unrealized gains (losses) on cash flow hedges, net of tax	7,004			7,004
Net unrealized gains (losses) on investments, net of tax	2			2
Proceeds from issuances under stock-based compensation plans, shares		1,418
Proceeds from issuances under stock-based compensation plans	23,042	$ 15	23,027
Repurchase of restricted common stock, shares		(80)
Repurchase of restricted common stock	0	$ 0
Cash dividends	(25,730)				(25,730)
Stock-based compensation	28,594		28,594
Tax benefit from stock-based awards	3,378		3,378
Repurchase of common stock, shares		(2,221)
Repurchase of common stock	(112,939)					(112,939)
Employees' tax withheld and paid for restricted stock and restricted stock units, shares		(165)
Employees' tax withheld and paid for restricted stock and restricted stock units	(7,611)	$ (2)				(7,609)
Other equity changes related to compensation	216		(634)			850
Common stock, shares, end of period at Mar. 31, 2015		41,601
Stockholders' equity, end of period at Mar. 31, 2015	727,397	$ 783	717,848	10,120	209,960	(211,314)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	68,392				68,392
Foreign currency translation adjustments	376			376
Net unrealized gains (losses) on cash flow hedges, net of tax	(6,680)			(6,680)
Net unrealized gains (losses) on investments, net of tax	(57)			(57)
Proceeds from issuances under stock-based compensation plans, shares		1,155
Proceeds from issuances under stock-based compensation plans	15,384	$ 10	15,374
Repurchase of restricted common stock, shares		(158)
Repurchase of restricted common stock	0	$ 0
Cash dividends	(21,061)				(21,061)
Stock-based compensation	33,265		33,265
Tax benefit from stock-based awards	3,515		3,515
Repurchase of common stock, shares		(9,077)
Repurchase of common stock	(497,393)					(497,393)
Employees' tax withheld and paid for restricted stock and restricted stock units, shares		(201)
Employees' tax withheld and paid for restricted stock and restricted stock units	(11,068)	$ 0				(11,068)
Other equity changes related to compensation	329		(513)			842
Common stock, shares, end of period at Mar. 31, 2016		33,320
Stockholders' equity, end of period at Mar. 31, 2016	312,399	$ 793	769,489	3,759	257,291	(718,933)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	82,599				82,599
Foreign currency translation adjustments	(311)			(311)
Net unrealized gains (losses) on cash flow hedges, net of tax	1,616			1,616
Net unrealized gains (losses) on investments, net of tax	(370)			(370)
Proceeds from issuances under stock-based compensation plans, shares		1,125
Proceeds from issuances under stock-based compensation plans	15,204	$ 11	15,193
Repurchase of restricted common stock, shares		(47)
Repurchase of restricted common stock	0	$ 0
Cash dividends	(19,959)				(19,959)
Stock-based compensation	33,539		33,539
Tax benefit from stock-based awards	546		546
Repurchase of common stock, shares		(764)
Repurchase of common stock	(34,236)					(34,236)
Employees' tax withheld and paid for restricted stock and restricted stock units, shares		(218)
Employees' tax withheld and paid for restricted stock and restricted stock units	(9,736)	$ 0				(9,736)
Other equity changes related to compensation	865		10			855
Common stock, shares, end of period at Mar. 31, 2017		33,416
Stockholders' equity, end of period at Mar. 31, 2017	$ 382,156	$ 804	$ 818,777	$ 4,694	$ 319,931	$ (762,050)