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, 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)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Reclassification of stranded income tax effects from accumulated other comprehensive income	(392)
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)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock for acquisition (in shares)		944,586
Issuance of common stock for acquisition	50,011	$ 944	49,067
Issuance of restricted shares (in shares)		77,755
Issuance of restricted shares	0	$ 78	(78)
Proceeds from exercise of stock options (in shares)		62,704
Proceeds from exercise of stock options	813	$ 63	750
Share-based compensation	897		897
Purchase of treasury shares (in shares)						17,976
Purchase of treasury shares	(960)					$ (960)
Net income	26,660			26,660
Dividends on common shares	(3,833)			(3,833)
Reclassification of stranded income tax effects from accumulated other comprehensive income				392	(392)
Other comprehensive income (loss) during the period	(9,151)				(9,151)
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)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of change in accounting principle	28			28
Balance at beginning of period (in shares) at Dec. 31, 2018		49,014,925				1,514,984
Balance at beginning of period at Dec. 31, 2018	1,456,347	$ 49,015	1,051,584	377,135	(4,826)	$ (16,561)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of restricted shares (in shares)		103,794
Issuance of restricted shares	915	$ 103	812
Proceeds from exercise of stock options (in shares)		7,708
Proceeds from exercise of stock options	54	$ 8	46
Share-based compensation	748		748
Purchase of treasury shares (in shares)						26,134
Purchase of treasury shares	(998)					$ (998)
Net income	39,905			39,905
Dividends on common shares	(4,759)			(4,759)
Other comprehensive income (loss) during the period	3,648				3,648
Balance at end of period (in shares) at Mar. 31, 2019		49,126,427				1,541,118
Balance at end of period at Mar. 31, 2019	$ 1,495,584	$ 49,126	$ 1,053,190	$ 412,005	$ (1,178)	$ (17,559)