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	32,223			32,223
Other comprehensive income (loss)	(20,728)				(20,728)
Dividends, declared (USD per share)	(16,630)			(16,630)
Discount on dividend reinvestment plan purchases	(84)		(84)
Treasury stock acquired	(30,001)					(30,001)
Treasury stock acquired, shares		(4,168,088)
Treasury stock reissued	176		0	0		176
Treasury stock reissued, shares		25,359
Restricted stock	393	0	68	2		323
Restricted stock, shares		58,000
Ending balance at Sep. 30, 2013	711,356	105,563	365,338	331,203	(19,469)	(71,279)
Ending balance, shares at Sep. 30, 2013		95,544,765
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	36,724			36,724
Other comprehensive income (loss)	10,912				10,912
Dividends, declared (USD per share)	(19,754)			(19,754)
Discount on dividend reinvestment plan purchases	(65)		(65)
Treasury stock acquired	(30,928)					(30,928)
Treasury stock acquired, shares		(3,633,513)
Treasury stock reissued	192		35	0		157
Treasury stock reissued, shares		21,960
Restricted stock	706	0	273	0		433
Restricted stock, shares		88,987
Ending balance at Sep. 30, 2014	$ 709,484	$ 105,563	$ 365,576	$ 351,718	$ (9,676)	$ (103,697)
Ending balance, shares at Sep. 30, 2014	91,722,649	91,722,649