Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Total
Beginning balance at Dec. 31, 2017	$ 295	$ 566,790	$ 168,148	$ 735,233
Beginning balance, shares at Dec. 31, 2017	29,503,000
Issuance of common stock, net	$ 14	30,933		30,947
Issuance of common stock, net, shares	1,439,000
Repurchase of common stock	$ (6)	(10,946)		(10,952)
Repurchase of common stock, shares	(604,000)
Repurchase of common stock upon vesting of restricted stock awards	$ (1)	(5,483)		(5,484)
Repurchase of common stock upon vesting of restricted stock awards, shares	(183,000)
Stock-based compensation expense		13,743		13,743
Net income			96,455	96,455
Ending balance at Dec. 31, 2018	$ 302	595,037	264,020	859,359
Ending balance, shares at Dec. 31, 2018	30,155,000
Adoption of ASC 606			(583)	(583)
Issuance of common stock, net	$ 27	79,025		79,052
Issuance of common stock, net, shares	2,717,000
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	430,000
Withholding of common stock upon vesting of restricted stock units	$ (1)	(3,582)		(3,583)
Withholding of common stock upon vesting of restricted stock units, shares	(152,000)
Stock-based compensation expense		15,316		15,316
Net income			112,994	112,994
Ending balance at Dec. 31, 2019	$ 331	684,354	377,014	1,061,699
Ending balance, shares at Dec. 31, 2019	33,067,000
Other		(385)		$ (385)
Repurchase of common stock, shares				0
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)	(5,098)		(5,100)
Withholding of common stock upon vesting of restricted stock units, shares	(170,000)
Stock-based compensation expense		18,334		18,334
Net income			206,157	206,157
Ending balance at Dec. 31, 2020	$ 334	$ 697,200	$ 583,171	$ 1,280,705
Ending balance, shares at Dec. 31, 2020	33,351,000