CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Loss
Beginning balance (in shares) at Mar. 31, 2018		30,447,000
Beginning balance at Mar. 31, 2018	$ 940,779	$ 304	$ 167,587	$ 785,871	$ (12,983)
Cumulative adjustment from adoption of new accounting guidance at Mar. 31, 2018	720			720
Increase (Decrease) in Stockholders' Equity
Stock compensation expense (in shares)		2,000
Stock compensation expense	3,526		3,526
Shares issued upon vesting (in shares)		6,000
Shares issued upon vesting	0
Shares withheld for taxes	(328)		(328)
Repurchases of common stock (in shares)		(86,000)
Repurchases of common stock	(9,999)			(9,999)
Net (loss) income	(30,407)			(30,407)
Total other comprehensive loss	(2,140)				(2,140)
Ending balance (in shares) at Jun. 30, 2018		30,369,000
Ending balance at Jun. 30, 2018	902,151	$ 304	170,785	746,185	(15,123)
Beginning balance (in shares) at Mar. 31, 2018		30,447,000
Beginning balance at Mar. 31, 2018	940,779	$ 304	167,587	785,871	(12,983)
Cumulative adjustment from adoption of new accounting guidance at Mar. 31, 2018	$ 720			720
Increase (Decrease) in Stockholders' Equity
Repurchases of common stock (in shares)	(1,400,699)
Repurchases of common stock	$ (161,395)
Net (loss) income	240,339
Total other comprehensive loss	(9,545)
Ending balance (in shares) at Dec. 31, 2018		29,128,000
Ending balance at Dec. 31, 2018	1,017,881	$ 291	174,821	865,297	(22,528)
Beginning balance (in shares) at Jun. 30, 2018		30,369,000
Beginning balance at Jun. 30, 2018	902,151	$ 304	170,785	746,185	(15,123)
Cumulative adjustment from adoption of new accounting guidance at Jun. 30, 2018	(252)			(252)
Increase (Decrease) in Stockholders' Equity
Stock compensation expense (in shares)		2,000
Stock compensation expense	3,926		3,926
Shares issued upon vesting (in shares)		65,000
Shares issued upon vesting	475	$ 1	474
Shares withheld for taxes	(4,091)		(4,091)
Repurchases of common stock (in shares)		(1,065,000)
Repurchases of common stock	(124,736)	$ (11)		(124,725)
Net (loss) income	74,372			74,372
Total other comprehensive loss	(5,058)				(5,058)
Ending balance (in shares) at Sep. 30, 2018		29,371,000
Ending balance at Sep. 30, 2018	846,787	$ 294	171,094	695,580	(20,181)
Increase (Decrease) in Stockholders' Equity
Stock compensation expense (in shares)		2,000
Stock compensation expense	4,037		4,037
Shares issued upon vesting (in shares)		5,000
Shares issued upon vesting	0
Shares withheld for taxes	(310)		(310)
Repurchases of common stock (in shares)		(250,000)
Repurchases of common stock	(26,660)	$ (3)		(26,657)
Net (loss) income	196,374			196,374
Total other comprehensive loss	(2,347)				(2,347)
Ending balance (in shares) at Dec. 31, 2018		29,128,000
Ending balance at Dec. 31, 2018	$ 1,017,881	$ 291	$ 174,821	$ 865,297	$ (22,528)