Condensed Consolidated Statements of Changes in Shareholders' Equity (Unaudited) (USD $) In Thousands, except Share data	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss), net [Member]	Treasury Stock [Member]
Beginning balance at Dec. 31, 2012	$ 746,007	$ 105,563	$ 365,354	$ 315,608	$ 1,259	$ (41,777)
Beginning balance, shares at Dec. 31, 2012		99,629,494
Net Income	16,369			16,369
Other comprehensive income (loss)	(17,981)				(17,981)
Dividends, Common Stock, Cash	(10,842)			(10,842)
Discount on dividend reinvestment plan purchases	(55)		(55)
Treasury stock acquired	(23,247)					(23,247)
Stock Issued During Period, Shares, Treasury Stock Reissued		25,359
Treasury stock acquired, shares		(3,267,692)
Stock Issued During Period, Value, Treasury Stock Reissued	176		0	0		176
Restricted stock, shares		55,000
Restricted stock	248		53	0		195
Ending balance at Jun. 30, 2013	710,675	105,563	365,352	321,135	(16,722)	(64,653)
Ending balance, shares at Jun. 30, 2013		96,442,161
Beginning balance at Dec. 31, 2013	711,697	105,563	365,333	334,748	(20,588)	(73,359)
Beginning balance, shares at Dec. 31, 2013	95,245,215	95,245,215
Net Income	24,228			24,228
Other comprehensive income (loss)	14,566				14,566
Dividends, Common Stock, Cash	(13,205)			(13,205)
Discount on dividend reinvestment plan purchases	(65)		(65)
Treasury stock acquired	(13,407)					(13,407)
Stock Issued During Period, Shares, Treasury Stock Reissued		21,960
Treasury stock acquired, shares		(1,603,350)
Stock Issued During Period, Value, Treasury Stock Reissued	192		35	0		157
Restricted stock, shares		88,987
Restricted stock	498		247	0		251
Ending balance at Jun. 30, 2014	$ 724,504	$ 105,563	$ 365,550	$ 345,771	$ (6,022)	$ (86,358)
Ending balance, shares at Jun. 30, 2014	93,752,812	93,752,812