Condensed Consolidated Statements of Changes in Shareholders' Equity (Unaudited) - USD ($) $ in Thousands	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	24,228			24,228
Other comprehensive income (loss)	14,566				14,566
Dividends, declared (USD per share)	(13,205)			(13,205)
Discount on dividend reinvestment plan purchases	(65)		(65)
Treasury stock acquired	(13,407)					(13,407)
Treasury stock acquired, shares		(1,603,350)
Treasury stock reissued	192		35	0		157
Treasury stock reissued, shares		21,960
Restricted stock	498	$ 0	247	0		251
Restricted stock, shares		88,987
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
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	$ 27,668			27,668
Other comprehensive income (loss)	4,359				4,359
Dividends, declared (USD per share)	(12,635)			(12,635)
Treasury stock acquired	(25,383)					(25,383)
Treasury stock acquired, shares		(2,918,066)
Treasury stock reissued	192		32	0		160
Treasury stock reissued, shares		20,936
Restricted stock	860	$ 0	286	0		574
Restricted stock, shares		134,370
Ending balance at Jun. 30, 2015	$ 711,206	$ 105,563	$ 365,933	$ 368,060	$ (140)	$ (128,210)
Ending balance, shares at Jun. 30, 2015	88,960,268	88,960,268