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	$ 9	25,808		25,817
Issuance of common stock, shares	899,000
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	$ (2)	(3,583)		$ (3,585)
Withholding of common stock upon vesting of restricted stock units, shares	(152,000)
Stock-based compensation expense		11,391		11,391
Net income			59,636	59,636
Ending balance at Sep. 30, 2019	$ 312	627,211	323,656	951,179
Ending balance, shares at Sep. 30, 2019	31,249,000
Beginning balance at Jun. 30, 2019	$ 304	600,293	296,632	897,229
Beginning balance, shares at Jun. 30, 2019	30,439,000
Issuance of common stock	$ 8	23,146		23,154
Issuance of common stock, shares	799,000
Repurchase of common stock				$ (1,400)
Repurchase of common stock, shares				(83,000)
Vesting of restricted stock units, shares	17,000
Withholding of common stock upon vesting of restricted stock units		(151)		$ (151)
Withholding of common stock upon vesting of restricted stock units, shares	(6,000)
Stock-based compensation expense		3,923		3,923
Net income			27,024	27,024
Ending balance at Sep. 30, 2019	$ 312	627,211	323,656	951,179
Ending balance, shares at Sep. 30, 2019	31,249,000
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		(311)		$ (311)
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		14,374		14,374
Net income			114,340	114,340
Ending balance at Sep. 30, 2020	$ 334	693,269	491,354	1,184,957
Ending balance, shares at Sep. 30, 2020	33,351,000
Beginning balance at Jun. 30, 2020	$ 334	687,564	441,590	1,129,488
Beginning balance, shares at Jun. 30, 2020	33,351,000
Other		(81)		$ (81)
Repurchase of common stock, shares
Stock-based compensation expense		5,786		$ 5,786
Net income			49,764	49,764
Ending balance at Sep. 30, 2020	$ 334	$ 693,269	$ 491,354	$ 1,184,957
Ending balance, shares at Sep. 30, 2020	33,351,000