Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Series H Preferred Stock	Common Stock	Non-Voting Common Stock	Common Stock Issuable	Capital Surplus	Retained Earnings (Accumulated Deficit)	Accumulated Other Comprehensive (Loss) Income
Beginning balance at Dec. 31, 2015	$ 1,018,285	$ 9,992	$ 66,198	$ 5,286	$ 6,779	$ 1,286,361	$ (330,879)	$ (25,452)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	100,656						100,656
Other comprehensive income (loss)	(1,031)							(1,031)
Common stock issued to Dividend Reinvestment Plan and employee benefit plans (25,248 common shares in 2018, 17,826 common shares in 2017, 20,500 common shares in 2016)	366		20			346
Conversion of non-voting common stock to voting common stock (5,285,516 shares)	0		5,286	(5,286)
Redemption of Series H preferred stock (9,992 shares)	(9,992)	(9,992)
Purchases of common stock (764,000 shares)	(13,659)		(764)			(12,895)
Amortization of stock options and restricted stock	4,496					4,496
Vesting of restricted stock awards, net of shares surrendered to cover payroll taxes (125,067 common shares issued and 99,779 common shares deferred in 2018, 114,837 common shares issued and 111,090 common shares deferred in 2017, 96,722 common shares issued and 106,771 common shares deferred in 2016)	(1,189)		97		1,597	(2,883)
Deferred compensation plan, net, including dividend equivalents	385				385
Shares issued from deferred compensation plan (48,214 shares in 2018, 32,279 shares in 2017, 61,899 shares in 2016)	0		62		(1,434)	1,372
Common stock dividends ($0.58 per share in 2018, $0.38 per share in 2017, $0.30 per share in 2016)	(21,613)						(21,613)
Tax on option exercise and restricted stock vesting	(948)					(948)
Preferred stock dividends, Series H	(21)						(21)
Ending balance at Dec. 31, 2016	1,075,735	0	70,899	0	7,327	1,275,849	(251,857)	(26,483)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	67,821						67,821
Other comprehensive income (loss)	3,269							3,269
Common stock issued to Dividend Reinvestment Plan and employee benefit plans (25,248 common shares in 2018, 17,826 common shares in 2017, 20,500 common shares in 2016)	450		18			432
Common stock issued for acquisitions (1,443,987 common shares in 2018, 6,515,505 common shares in 2017)	179,465		6,516			172,949
Amortization of stock options and restricted stock	5,827					5,827
Vesting of restricted stock awards, net of shares surrendered to cover payroll taxes (125,067 common shares issued and 99,779 common shares deferred in 2018, 114,837 common shares issued and 111,090 common shares deferred in 2017, 96,722 common shares issued and 106,771 common shares deferred in 2016)	(1,594)		115		1,763	(3,472)
Deferred compensation plan, net, including dividend equivalents	361				361
Shares issued from deferred compensation plan (48,214 shares in 2018, 32,279 shares in 2017, 61,899 shares in 2016)	(107)		32		(368)	229
Common stock dividends ($0.58 per share in 2018, $0.38 per share in 2017, $0.30 per share in 2016)	(28,330)						(28,330)
Reclassification of disproportionate tax effects resulting from the Tax Cuts and Jobs Act of 2017 pursuant to ASU 2018-02	0						2,027	(2,027)
Ending balance at Dec. 31, 2017	1,303,334	0	77,580	0	9,083	1,451,814	(209,902)	(25,241)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	166,111						166,111
Other comprehensive income (loss)	(16,348)							(16,348)
Common stock issued to Dividend Reinvestment Plan and employee benefit plans (25,248 common shares in 2018, 17,826 common shares in 2017, 20,500 common shares in 2016)	679		25			654
Common stock issued for acquisitions (1,443,987 common shares in 2018, 6,515,505 common shares in 2017)	45,746		1,444			44,302
Amortization of stock options and restricted stock	6,057					6,057
Exercise of stock options (12,000 shares)	142		12			130
Vesting of restricted stock awards, net of shares surrendered to cover payroll taxes (125,067 common shares issued and 99,779 common shares deferred in 2018, 114,837 common shares issued and 111,090 common shares deferred in 2017, 96,722 common shares issued and 106,771 common shares deferred in 2016)	(1,988)		125		1,931	(4,044)
Deferred compensation plan, net, including dividend equivalents	459				459
Shares issued from deferred compensation plan (48,214 shares in 2018, 32,279 shares in 2017, 61,899 shares in 2016)	(10)		48		(729)	671
Common stock dividends ($0.58 per share in 2018, $0.38 per share in 2017, $0.30 per share in 2016)	(46,628)						(46,628)
Ending balance at Dec. 31, 2018	$ 1,457,554	$ 0	$ 79,234	$ 0	$ 10,744	$ 1,499,584	$ (90,419)	$ (41,589)