CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS’ EQUITY - USD ($) $ in Thousands	Total	Common Stock	Capital Surplus	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
Equity, beginning balance (in shares) at Dec. 31, 2014		26,176
Equity, beginning balance at Dec. 31, 2014	$ 288,405	$ 262	$ 252,421	$ 34,660	$ 1,062
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	15,439			15,439
Net change in unrealized gains and losses on available-for-sale securities, net of taxes and reclassification adjustment	(645)				(645)
Issuance of common stock in connection with the acquisition of Patriot Bancshares, Inc. (in shares)		10,442
Issuance of common stock in connection with the acquisition of Patriot Bancshares, Inc.	123,743	$ 105	123,638
Issuance of common stock in connection with exercise of stock options (in shares)		170
Issuance of common stock in connection with exercise of stock options	1,534	$ 1	1,533
Stock-based compensation expense	926		926
Equity, ending balance at Dec. 31, 2015	429,402	$ 368	378,518	50,099	417
Equity, ending balance (in shares) at Dec. 31, 2015		36,788
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(972)			(972)
Net change in unrealized gains and losses on available-for-sale securities, net of taxes and reclassification adjustment	(1,142)				(1,142)
Issuance of common stock in connection with the acquisition of Patriot Bancshares, Inc.	0
Purchase of treasury stock (in shares)		(178)
Purchase of treasury stock	(1,253)					$ (1,253)
Issuance of common stock in connection with exercise of stock options (in shares)		378
Issuance of common stock in connection with exercise of stock options	3,046	$ 4	3,042
Stock-based compensation expense	1,401		1,401
Equity, ending balance at Dec. 31, 2016	430,482	$ 372	382,961	49,127	(725)	(1,253)
Equity, ending balance (in shares) at Dec. 31, 2016		36,988
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	34,136			34,136
Net change in unrealized gains and losses on available-for-sale securities, net of taxes and reclassification adjustment	(5,754)				(5,754)
Issuance of common stock in connection with the acquisition of Patriot Bancshares, Inc.	0
Issuance of common stock in connection with exercise of stock options (in shares)		115
Issuance of common stock in connection with exercise of stock options	486	$ 1	485
Stock-based compensation expense	4,445		4,445
Equity, ending balance at Dec. 31, 2017	$ 463,795	$ 373	$ 387,891	$ 83,263	$ (6,479)	$ (1,253)
Equity, ending balance (in shares) at Dec. 31, 2017		37,103