Consolidated Statements of Equity - USD ($) shares in Thousands, $ in Thousands	Common Stock [Member]	Paid-In Capital [Member]	Retained Earnings [Member]	Total
Beginning balance at Dec. 31, 2015	$ 213	$ 340,953	$ 68,313	$ 409,479
Beginning balance (in shares) at Dec. 31, 2015	21,304
Issuance of common stock	$ 6	11,363		11,369
Issuance of common stock, shares	578
Repurchase of common stock	$ (2)	(2,391)		(2,393)
Repurchase of common stock, shares	(159)
Repurchase of common stock upon vesting of restricted stock awards	$ (1)	(1,015)		(1,016)
Repurchase of common stock upon vesting of restricted stock awards, shares	(60)
Stock-based compensation expense		6,657		6,657
Forfeitures of restricted stock awards, shares	(42)
Net income			49,540	49,540
Ending balance at Dec. 31, 2016	$ 216	355,567	117,853	473,636
Ending balance (in shares) at Dec. 31, 2016	21,621
Issuance of common stock	$ 39	97,301		97,340
Issuance of common stock, shares	3,897
Issuance of common stock in connection with business combination	$ 42	107,737		107,779
Issuance of common stock in connection with business combination, shares	4,176
Replacement award value in connection with business combination		1,149		1,149
Repurchase of common stock upon vesting of restricted stock awards	$ (2)	(4,506)		(4,508)
Repurchase of common stock upon vesting of restricted stock awards, shares	(189)
Stock-based compensation expense		9,542		9,542
Forfeitures of restricted stock awards, shares	(2)
Net income			50,295	50,295
Ending balance at Dec. 31, 2017	$ 295	566,790	168,148	735,233
Ending balance (in shares) at Dec. 31, 2017	29,503
Issuance of common stock	$ 14	30,933		30,947
Issuance of common stock, shares	1,439
Repurchase of common stock	$ (6)	(10,946)		(10,952)
Repurchase of common stock, shares	(604)
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)
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 (in shares) at Dec. 31, 2018	30,155
Adoption of ASC 606			$ (583)	$ (583)