CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (UNAUDITED) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive (Loss) Income
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)
Increase (Decrease) in Stockholders' Equity
Stock-based compensation (in shares)		2,000
Stock-based compensation	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 income (loss)	(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)
Increase (Decrease) in Stockholders' Equity
Net income (loss)	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)
Increase (Decrease) in Stockholders' Equity
Stock-based compensation (in shares)		2,000
Stock-based compensation	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 income (loss)	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-based compensation (in shares)		2,000
Stock-based compensation	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 income (loss)	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)
Beginning balance (in shares) at Mar. 31, 2019		29,141,000
Beginning balance at Mar. 31, 2019	1,045,130	$ 291	178,227	889,266	(22,654)
Increase (Decrease) in Stockholders' Equity
Stock-based compensation (in shares)		1,000
Stock-based compensation	3,424		3,424
Shares issued upon vesting (in shares)		4,000
Shares issued upon vesting	0
Exercise of stock options (in shares)		46,000
Exercise of stock options	2,773	$ 1	2,772
Shares withheld for taxes	(374)		(374)
Repurchases of common stock (in shares)		(227,000)
Repurchases of common stock	(35,005)	$ (2)		(35,003)
Net income (loss)	(19,351)			(19,351)
Total other comprehensive loss	(249)				(249)
Ending balance (in shares) at Jun. 30, 2019		28,965,000
Ending balance at Jun. 30, 2019	995,279	$ 290	184,049	833,843	(22,903)
Beginning balance (in shares) at Mar. 31, 2019		29,141,000
Beginning balance at Mar. 31, 2019	$ 1,045,130	$ 291	178,227	889,266	(22,654)
Increase (Decrease) in Stockholders' Equity
Repurchases of common stock (in shares)	(1,296,201)
Repurchases of common stock	$ (190,405)
Net income (loss)	260,052
Total other comprehensive loss	(449)
Ending balance (in shares) at Dec. 31, 2019		27,982,000
Ending balance at Dec. 31, 2019	1,123,747	$ 280	188,713	957,857	(23,103)
Beginning balance (in shares) at Jun. 30, 2019		28,965,000
Beginning balance at Jun. 30, 2019	995,279	$ 290	184,049	833,843	(22,903)
Increase (Decrease) in Stockholders' Equity
Stock-based compensation (in shares)		3,000
Stock-based compensation	5,075		5,075
Shares issued upon vesting (in shares)		73,000
Shares issued upon vesting	618	$ 1	617
Exercise of stock options (in shares)		3,000
Exercise of stock options	186		186
Shares withheld for taxes	(5,370)		(5,370)
Repurchases of common stock (in shares)		(1,069,000)
Repurchases of common stock	(155,400)	$ (11)		(155,389)
Net income (loss)	77,810			77,810
Total other comprehensive loss	(1,894)				(1,894)
Ending balance (in shares) at Sep. 30, 2019		27,975,000
Ending balance at Sep. 30, 2019	916,304	$ 280	184,557	756,264	(24,797)
Increase (Decrease) in Stockholders' Equity
Stock-based compensation (in shares)		1,000
Stock-based compensation	4,221		4,221
Shares issued upon vesting (in shares)		3,000
Shares issued upon vesting	0
Exercise of stock options (in shares)		3,000
Exercise of stock options	186		186
Shares withheld for taxes	(251)		(251)
Net income (loss)	201,593			201,593
Total other comprehensive loss	1,694				1,694
Ending balance (in shares) at Dec. 31, 2019		27,982,000
Ending balance at Dec. 31, 2019	$ 1,123,747	$ 280	$ 188,713	$ 957,857	$ (23,103)