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, 2013	$ 711,697	$ 105,563	$ 365,333	$ 334,748	$ (20,588)	$ (73,359)
Beginning balance, shares at Dec. 31, 2013		95,245,215
Net Income	12,300			12,300
Other comprehensive income (loss)	8,096				8,096
Dividends, declared (USD per share)	(6,618)			(6,618)
Discount on dividend reinvestment plan purchases	(33)		(33)
Treasury stock acquired	(8,941)					(8,941)
Treasury stock acquired, shares		(1,084,958)
Restricted stock	282	0	169	0		113
Restricted stock, shares		63,626
Ending balance at Mar. 31, 2014	716,783	105,563	365,469	340,430	(12,492)	(82,187)
Ending balance, shares at Mar. 31, 2014		94,223,883
Beginning balance at Dec. 31, 2014	716,145	105,563	365,615	353,027	(4,499)	(103,561)
Beginning balance, shares at Dec. 31, 2014	91,723,028	91,723,028
Net Income	14,221			14,221
Other comprehensive income (loss)	7,201				7,201
Dividends, declared (USD per share)	(6,407)			(6,407)
Treasury stock acquired	(18,874)					(18,874)
Treasury stock acquired, shares		(2,201,391)
Restricted stock	574	0	259	0		315
Restricted stock, shares		134,370
Ending balance at Mar. 31, 2015	$ 712,860	$ 105,563	$ 365,874	$ 360,841	$ 2,702	$ (122,120)
Ending balance, shares at Mar. 31, 2015	89,656,007	89,656,007