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]	Previously Reported [Member]	Previously Reported [Member] Common Stock [Member]	Previously Reported [Member] Additional Paid-in Capital [Member]	Previously Reported [Member] Retained Earnings [Member]	Previously Reported [Member] Accumulated Other Comprehensive Income (Loss), net [Member]	Previously Reported [Member] Treasury Stock [Member]	Effect of ASU Adoption [Member]	Effect of ASU Adoption [Member] Retained Earnings [Member]	Effect of ASU Adoption [Member] Accumulated Other Comprehensive Income (Loss), net [Member]
Cumulative effect of adoption of ASU 2018-02													$ 0	$ 1,344	$ (1,344)
Beginning balance at Dec. 31, 2017	$ 888,127	$ 113,915	$ 470,123	$ 438,760	$ (7,517)	$ (127,154)	$ 888,127	$ 113,915	$ 470,123	$ 437,416	$ (6,173)	$ (127,154)
Beginning balance, shares at Dec. 31, 2017	97,456,478	97,456,478						97,456,478
Net Income	$ 80,500			80,500
Other comprehensive income (loss)	(13,140)				(13,140)
Dividends, declared (USD per share)	(25,868)			(25,868)
Treasury stock acquired	(1,136)					(1,136)
Treasury stock acquired, shares		(75,778)
Stock Issued During Period, Value, Treasury Stock Reissued	44,026		21,579	0		22,447
Stock Issued During Period, Shares, Treasury Stock Reissued		2,908,234
Restricted stock	422	$ 0	560	0		(138)
Restricted stock, shares		72,500
Stock Issued During Period, Value, Treasury Stock Reissued	2,257
Ending balance at Sep. 30, 2018	$ 972,931	$ 113,915	$ 492,262	$ 493,392	$ (20,657)	$ (105,981)
Ending balance, shares at Sep. 30, 2018	100,361,434	100,361,434