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	(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)		10,124,491
Issuance of common stock for acquisitions	547,127	$ 10,124	537,003
Issuance of restricted shares (in shares)		85,855
Issuance of restricted shares	0	$ 86	(86)
Forfeitures of restricted shares (in shares)		(472)
Forfeitures of restricted shares	0
Proceeds from exercise of stock options (in shares)		67,203
Proceeds from exercise of stock options	846	$ 67	779
Share-based compensation	3,183		3,183
Purchase of treasury shares (in shares)						18,427
Purchase of treasury shares	(985)					$ (985)
Net income	36,047			36,047
Dividends on common shares	(7,930)			(7,930)
Reclassification of stranded income tax effects				392	(392)
Other comprehensive income (loss) during the period	(10,899)				(10,899)
Balance at end of period (in shares) at Jun. 30, 2018		49,011,950				1,493,288
Balance at end of period at Jun. 30, 2018	1,371,896	$ 49,012	1,049,283	301,656	(12,571)	$ (15,484)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of change in accounting principle	28			28
Balance at beginning of period (in shares) at Mar. 31, 2018		39,819,918				1,492,837
Balance at beginning 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]
Issuance of common stock for acquisition (in shares)		9,179,905
Issuance of common stock for acquisitions	497,116	$ 9,180	487,936
Issuance of restricted shares (in shares)		8,100
Issuance of restricted shares	0	$ 8	(8)
Forfeitures of restricted shares (in shares)		(472)
Forfeitures of restricted shares	0
Proceeds from exercise of stock options (in shares)		4,499
Proceeds from exercise of stock options	33	$ 4	29
Share-based compensation	2,286		2,286
Purchase of treasury shares (in shares)						451
Purchase of treasury shares	(25)					$ (25)
Net income	9,387			9,387
Dividends on common shares	(4,097)			(4,097)
Other comprehensive income (loss) during the period	(1,748)				(1,748)
Balance at end of period (in shares) at Jun. 30, 2018		49,011,950				1,493,288
Balance at end of period at Jun. 30, 2018	1,371,896	$ 49,012	1,049,283	301,656	(12,571)	$ (15,484)
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)		117,122
Issuance of restricted shares	915	$ 116	799
Forfeitures of restricted shares (in shares)		(40,423)
Forfeitures of restricted shares	(524)	$ (40)	(484)
Proceeds from exercise of stock options (in shares)		7,708
Proceeds from exercise of stock options	54	$ 8	46
Share-based compensation	1,555		1,555
Purchase of treasury shares (in shares)						322,764
Purchase of treasury shares	(11,561)					$ (11,561)
Net income	78,809			78,809
Dividends on common shares	(9,486)			(9,486)
Other comprehensive income (loss) during the period	21,288				21,288
Balance at end of period (in shares) at Jun. 30, 2019		49,099,332				1,837,748
Balance at end of period at Jun. 30, 2019	1,537,121	$ 49,099	1,053,500	446,182	16,462	$ (28,122)
Balance at beginning of period (in shares) at Mar. 31, 2019		49,126,427				1,541,118
Balance at beginning of period at Mar. 31, 2019	1,495,584	$ 49,126	1,053,190	412,005	(1,178)	$ (17,559)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of restricted shares (in shares)		13,328
Issuance of restricted shares	0	$ 13	(13)
Forfeitures of restricted shares (in shares)		(40,423)
Forfeitures of restricted shares	(524)	$ (40)	(484)
Share-based compensation	807		807
Purchase of treasury shares (in shares)						296,630
Purchase of treasury shares	(10,563)					$ (10,563)
Net income	38,904			38,904
Dividends on common shares	(4,727)			(4,727)
Other comprehensive income (loss) during the period	17,640				17,640
Balance at end of period (in shares) at Jun. 30, 2019		49,099,332				1,837,748
Balance at end of period at Jun. 30, 2019	$ 1,537,121	$ 49,099	$ 1,053,500	$ 446,182	$ 16,462	$ (28,122)