CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Balance at Dec. 31, 2016	$ 459,740	$ 274	$ 345,138	$ 117,049	$ (2,721)
Balance (in shares) at Dec. 31, 2016		27,798,283
Increase (Decrease) in Stockholders' Equity
Net income	9,521			9,521
Other comprehensive income	1,013				1,013
Share-based compensation expense	1,154		1,154
Issuance of restricted stock, net (in shares)		56,866
Repurchase of common stock	(904)		(904)
Repurchase of common stock (in shares)		0
Exercise of stock options	501	$ 1	500
Exercise of stock options (in shares)		53,667
Balance at Mar. 31, 2017	471,025	$ 275	345,888	126,570	(1,708)
Balance (in shares) at Mar. 31, 2017		27,908,816
Balance at Dec. 31, 2017	$ 1,241,996	$ 458	1,063,974	177,149	415
Balance (in shares) at Dec. 31, 2017	46,245,050	46,245,050
Increase (Decrease) in Stockholders' Equity
Net income	$ 28,002			28,002
Other comprehensive income	(9,348)				(9,348)
Share-based compensation expense	1,712		1,712
Issuance of restricted stock, net	0		0
Issuance of restricted stock, net (in shares)		197,422
Repurchase of common stock	(1,538)		(1,538)
Repurchase of common stock (in shares)		(26,168)
Exercise of stock options	1,084	$ 14	1,070
Exercise of stock options (in shares)		111,262
Reclassification of certain tax effects of the Tax Cuts and Jobs Act	0			(82)	82
Balance at Mar. 31, 2018	$ 1,261,908	$ 472	$ 1,065,218	$ 205,069	$ (8,851)
Balance (in shares) at Mar. 31, 2018	46,527,566	46,527,566