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 acquisition	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	4,652		4,652
Purchase of treasury shares (in shares)						40,123
Purchase of treasury shares	(2,062)					$ (2,062)
Net income	77,491			77,491
Dividends on common shares	(12,680)			(12,680)
Reclassification of stranded income tax effects				392	(392)
Other comprehensive income (loss) during the period	(14,904)				(14,904)
Balance at end of period (in shares) at Sep. 30, 2018		49,011,950				1,514,984
Balance at end of period at Sep. 30, 2018	1,404,977	$ 49,012	1,050,752	338,350	(16,576)	$ (16,561)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of change in accounting principle	28			28
Balance at beginning of period (in shares) at Jun. 30, 2018		49,011,950				1,493,288
Balance at beginning 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]
Share-based compensation	1,469		1,469
Purchase of treasury shares (in shares)						21,696
Purchase of treasury shares	(1,077)					$ (1,077)
Net income	41,444			41,444
Dividends on common shares	(4,750)			(4,750)
Other comprehensive income (loss) during the period	(4,005)				(4,005)
Balance at end of period (in shares) at Sep. 30, 2018		49,011,950				1,514,984
Balance at end of period at Sep. 30, 2018	1,404,977	$ 49,012	1,050,752	338,350	(16,576)	$ (16,561)
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 common stock for acquisition (in shares)		22,181,522
Issuance of common stock for acquisition	869,294	$ 22,182	847,112
Issuance of restricted shares (in shares)		147,574
Issuance of restricted shares	915	$ 147	768
Forfeitures of restricted shares (in shares)		(40,423)
Forfeitures of restricted shares	(524)	$ (40)	(484)
Proceeds from exercise of stock options (in shares)		127,983
Proceeds from exercise of stock options	3,587	$ 143	3,444
Share-based compensation	2,365		2,365
Purchase of treasury shares (in shares)						322,764
Purchase of treasury shares	(11,561)					$ (11,561)
Net income	100,193			100,193
Dividends on common shares	(19,925)			(19,925)
Other comprehensive income (loss) during the period	20,308				20,308
Balance at end of period (in shares) at Sep. 30, 2019		71,431,581				1,837,748
Balance at end of period at Sep. 30, 2019	2,420,723	$ 71,447	1,904,789	457,127	15,482	$ (28,122)
Balance at beginning of period (in shares) at Jun. 30, 2019		49,099,332				1,837,748
Balance at beginning of period at Jun. 30, 2019	1,537,121	$ 49,099	1,053,500	446,182	16,462	$ (28,122)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock for acquisition (in shares)		22,181,522
Issuance of common stock for acquisition	869,294	$ 22,182	847,112
Issuance of restricted shares (in shares)		30,452
Issuance of restricted shares	0	$ 30	(30)
Proceeds from exercise of stock options (in shares)		120,275
Proceeds from exercise of stock options	3,534	$ 136	3,398
Share-based compensation	809		809
Net income	21,384			21,384
Dividends on common shares	(10,439)			(10,439)
Other comprehensive income (loss) during the period	(980)				(980)
Balance at end of period (in shares) at Sep. 30, 2019		71,431,581				1,837,748
Balance at end of period at Sep. 30, 2019	$ 2,420,723	$ 71,447	$ 1,904,789	$ 457,127	$ 15,482	$ (28,122)