Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Common Stock	Additional Paid-In Capital	Retained Earnings	Total
Beginning balance at Dec. 31, 2018	$ 302	$ 595,037	$ 264,020	$ 859,359
Beginning balance, shares at Dec. 31, 2018	30,155,000
Issuance of common stock	$ 1	2,662		2,663
Issuance of common stock, shares	100,000
Repurchase of common stock	$ (1)	(1,438)		$ (1,439)
Repurchase of common stock, shares	(83,000)			(83,000)
Vesting of restricted stock units	$ 4	(4)
Vesting of restricted stock units, shares	413,000
Withholding of common stock upon vesting of restricted stock units	$ (2)	(3,432)		$ (3,434)
Withholding of common stock upon vesting of restricted stock units, shares	(146,000)
Stock-based compensation expense		7,468		7,468
Net income			32,612	32,612
Ending balance at Jun. 30, 2019	$ 304	600,293	296,632	897,229
Ending balance, shares at Jun. 30, 2019	30,439,000
Beginning balance at Mar. 31, 2019	$ 303	593,966	281,137	875,406
Beginning balance, shares at Mar. 31, 2019	30,304,000
Issuance of common stock	$ 1	2,662		2,663
Issuance of common stock, shares	100,000
Repurchase of common stock				$ (1,400)
Repurchase of common stock, shares				(83,000)
Vesting of restricted stock units, shares	45,000
Withholding of common stock upon vesting of restricted stock units		(268)		$ (268)
Withholding of common stock upon vesting of restricted stock units, shares	(10,000)
Stock-based compensation expense		3,933		3,933
Net income			15,495	15,495
Ending balance at Jun. 30, 2019	$ 304	600,293	296,632	897,229
Ending balance, shares at Jun. 30, 2019	30,439,000
Beginning balance at Dec. 31, 2019	$ 331	684,354	377,014	1,061,699
Beginning balance, shares at Dec. 31, 2019	33,067,000
Other		(230)		$ (230)
Repurchase of common stock, shares
Vesting of restricted stock units	$ 5	(5)
Vesting of restricted stock units, shares	454,000
Withholding of common stock upon vesting of restricted stock units	$ (2)	(5,143)		$ (5,145)
Withholding of common stock upon vesting of restricted stock units, shares	(170,000)
Stock-based compensation expense		8,588		8,588
Net income			64,576	64,576
Ending balance at Jun. 30, 2020	$ 334	687,564	441,590	1,129,488
Ending balance, shares at Jun. 30, 2020	33,351,000
Beginning balance at Mar. 31, 2020	$ 333	681,060	403,140	1,084,533
Beginning balance, shares at Mar. 31, 2020	33,319,000
Other		(230)		$ (230)
Repurchase of common stock, shares
Vesting of restricted stock units	$ 1	(1)
Vesting of restricted stock units, shares	42,000
Withholding of common stock upon vesting of restricted stock units		(168)		$ (168)
Withholding of common stock upon vesting of restricted stock units, shares	(10,000)
Stock-based compensation expense		6,903		6,903
Net income			38,450	38,450
Ending balance at Jun. 30, 2020	$ 334	$ 687,564	$ 441,590	$ 1,129,488
Ending balance, shares at Jun. 30, 2020	33,351,000