CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Retained Earnings	Accumulated Other Comprehensive (Loss) Income
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	43,929			43,929
Other comprehensive income	5,197				5,197
Share-based compensation expense	4,246		4,246
Issuance of restricted stock, net (in shares)		149,197
Common stock issued	464,982	$ 120	464,862
Common stock issued (in shares)		11,904,901
Restricted stock surrendered and canceled	(1,259)		(1,259)
Restricted stock surrendered and canceled (in shares)		(21,506)
Exercise of stock options	4,325	$ 3	4,322
Exercise of stock options (in shares)		331,151
Balance at Sep. 30, 2017	981,160	$ 397	817,309	160,978	2,476
Balance (in shares) at Sep. 30, 2017		40,162,026
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	$ 83,697			83,697
Other comprehensive income	(17,174)				(17,174)
Share-based compensation expense	6,362		6,362
Issuance of restricted stock, net	0		0
Issuance of restricted stock, net (in shares)		264,420
Common stock issued	601,171	$ 158	601,013
Common stock issued (in shares)		15,758,039
Restricted stock surrendered and canceled	(1,586)		(1,586)
Restricted stock surrendered and canceled (in shares)		(28,849)
Exercise of stock options	1,911	$ 1	1,910
Exercise of stock options (in shares)		234,061
Reclassification of certain tax effects of the Tax Cuts and Jobs Act	0			(82)	82
Balance at Sep. 30, 2018	$ 1,916,377	$ 617	$ 1,671,673	$ 260,764	$ (16,677)
Balance (in shares) at Sep. 30, 2018	62,472,721	62,472,721