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, 2015		33,292
Beginning 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)
New ASU impact at Mar. 31, 2017	1,558			1,558
Increase (Decrease) in Stockholders' Equity
Stock compensation expense (in shares)		15
Stock compensation expense	14,302		14,302
Shares issued upon vesting (in shares)		148
Shares issued upon vesting	765	$ 1	764
Shares withheld for taxes	(8,276)		(8,276)
Stock repurchase (in shares)		(1,703)
Repurchases of common stock	(149,687)	$ (17)		(149,670)
Net income	114,394			114,394
Total other comprehensive loss	13,468				13,468
Ending balance (in shares) at Mar. 31, 2018		30,447
Ending balance at Mar. 31, 2018	$ 940,779	$ 304	$ 167,587	$ 785,871	$ (12,983)