Consolidated Statements of Shareholders’ Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Capital Surplus	Retained Earnings	Accumulated Other Comprehensive Income (Loss), Net of Tax	Treasury Stock
Balance at beginning of period (in shares) at Dec. 31, 2016		36,377,807				1,456,333
Balance at beginning of period at Dec. 31, 2016		$ 36,378	$ 410,276	$ 214,454	$ (1,058)	$ (13,613)
Cumulative effect of change in accounting for derivatives at Dec. 31, 2016				0
Adjusted balance at beginning of period at Dec. 31, 2016				214,454	(1,058)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Reclassification to retained earnings due to change in federal corporate tax rate				0	0
Share-based compensation			673
Issuance of common stock (in shares)		2,141,072
Issuance of common stock		$ 2,141	92,359
Issuance of restricted shares (in shares)		67,721
Issuance of restricted shares		$ 68	(68)
Exercise of stock options (in shares)		16,349
Proceeds from exercise of stock options		$ 16	303
Net income	$ 21,153			21,153
Dividends on common shares				(3,713)
Other comprehensive income during the period	(151)				(151)
Purchase of treasury shares (in shares)						17,902
Purchase of treasury shares						$ (1,002)
Balance at end of period (in shares) at Mar. 31, 2017		38,602,949				1,474,235
Balance at end of period at Mar. 31, 2017	758,216	$ 38,603	503,543	231,894	(1,209)	$ (14,615)
Balance at beginning of period (in shares) at Dec. 31, 2017		38,734,873				1,474,861
Balance at beginning of period at Dec. 31, 2017	804,479	$ 38,735	508,404	273,119	(1,280)	$ (14,499)
Cumulative effect of change in accounting for derivatives at Dec. 31, 2017				28
Adjusted balance at beginning of period at Dec. 31, 2017	(1,672)			273,539	(1,672)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Reclassification to retained earnings due to change in federal corporate tax rate	(392)			392	(392)
Share-based compensation			897
Issuance of common stock (in shares)		944,586
Issuance of common stock		$ 944	49,067
Issuance of restricted shares (in shares)		77,755
Issuance of restricted shares		$ 78	(78)
Exercise of stock options (in shares)		62,704
Proceeds from exercise of stock options		$ 63	750
Net income	26,660			26,660
Dividends on common shares				(3,833)
Other comprehensive income during the period	(9,151)				(9,151)
Purchase of treasury shares (in shares)						17,976
Purchase of treasury shares						$ (960)
Balance at end of period (in shares) at Mar. 31, 2018		39,819,918				1,492,837
Balance at end of period at Mar. 31, 2018	$ 868,944	$ 39,820	$ 559,040	$ 296,366	$ (10,823)	$ (15,459)