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, 2015	$ 719,546	$ 105,563	$ 365,981	$ 378,081	$ (2,386)	$ (127,693)
Beginning balance, shares at Dec. 31, 2015		88,961,268
Net Income	41,676			41,676
Other comprehensive income (loss)	9,148				9,148
Dividends, declared (USD per share)	(18,678)			(18,678)
Treasury stock acquired	(864)					(864)
Treasury stock acquired, shares		(98,687)
Stock Issued During Period, Value, Treasury Stock Reissued	216		39	0		177
Stock Issued During Period, Shares, Treasury Stock Reissued		23,148
Restricted stock	743	$ 0	271	0		472
Restricted stock, shares		106,348
Stock Issued During Period, Value, Treasury Stock Reissued	0
Ending balance at Sep. 30, 2016	751,787	$ 105,563	366,291	401,079	6,762	(127,908)
Ending balance, shares at Sep. 30, 2016		88,992,077
Beginning balance at Dec. 31, 2016	$ 749,929	$ 105,563	366,426	412,764	(7,027)	(127,797)
Beginning balance, shares at Dec. 31, 2016	88,961,268	89,007,077
Net Income	$ 51,184			51,184
Other comprehensive income (loss)	3,056				3,056
Dividends, declared (USD per share)	(22,717)			(22,717)
Treasury stock acquired	(1,187)					(1,187)
Treasury stock acquired, shares		(85,160)
Stock Issued During Period, Value, Treasury Stock Reissued	2,557		1,170	0		1,387
Stock Issued During Period, Shares, Treasury Stock Reissued		181,211
Restricted stock	738	$ 0	138	0		600
Restricted stock, shares		21,000
Stock Issued During Period, Value, Treasury Stock Reissued	2,258
Conversion of Stock, Shares Issued		8,351,447
Ending balance at Sep. 30, 2017	$ 894,301	$ 113,915	470,123	$ 441,231	$ (3,971)	$ (126,997)
Ending balance, shares at Sep. 30, 2017	97,475,575	97,475,575
Stock Issued During Period, Value, Other	$ 110,741	$ 8,352	$ 102,389