CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Loss
Beginning balance (in shares) at Mar. 31, 2014		34,624
Beginning balance at Mar. 31, 2014	$ 888,849	$ 346	$ 146,731	$ 743,815	$ (2,043)
Increase (Decrease) in Stockholders' Equity
Stock compensation expense (in shares)		11
Stock compensation expense	13,524		13,524
Shares issued upon vesting (in shares)		93
Shares issued upon vesting	0	$ 1	(1)
Excess tax benefit from stock compensation	4,197		4,197
Shares withheld for taxes	(5,674)		(5,674)
Stock repurchase (in shares)		(1,436)
Repurchases of common stock	(107,239)	$ (14)		(107,225)
Net income	161,780			161,780
Total other comprehensive loss	(18,425)				(18,425)
Ending balance (in shares) at Mar. 31, 2015		33,292
Ending balance at Mar. 31, 2015	937,012	$ 333	158,777	798,370	(20,468)
Increase (Decrease) in Stockholders' Equity
Stock compensation expense (in shares)		16
Stock compensation expense	6,622		6,622
Shares issued upon vesting (in shares)		132
Shares issued upon vesting	0	$ 1	(1)
Excess tax benefit from stock compensation	471		471
Shares withheld for taxes	(4,610)		(4,610)
Stock repurchase (in shares)		(1,420)
Repurchases of common stock	(94,200)	$ (14)		(94,186)
Net income	122,265			122,265
Total other comprehensive loss	(89)				(89)
Ending balance (in shares) at Mar. 31, 2016		32,020
Ending balance at Mar. 31, 2016	967,471	$ 320	161,259	826,449	(20,557)
Increase (Decrease) in Stockholders' Equity
Stock compensation expense (in shares)		23
Stock compensation expense	6,175		6,175
Shares issued upon vesting (in shares)		166
Shares issued upon vesting	798	$ 2	796
Excess tax benefit from stock compensation	100		100
Shares withheld for taxes	(7,533)		(7,533)
Stock repurchase (in shares)		(222)
Repurchases of common stock	(12,572)	$ (2)		(12,570)
Net income	5,710			5,710
Total other comprehensive loss	(5,894)				(5,894)
Ending balance (in shares) at Mar. 31, 2017		31,987
Ending balance at Mar. 31, 2017	$ 954,255	$ 320	$ 160,797	$ 819,589	$ (26,451)