Consolidated Statements of Changes In Stockholders' Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Treasury Stock
Balance Beginning at Dec. 31, 2014	$ 1,100,775	$ 882	$ 449,798	$ 899,516	$ (15,855)	$ (233,566)
Balance Beginning (in Shares) at Dec. 31, 2014		77,695
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	42,456			42,456
Other comprehensive income	(5,377)				(5,377)
Common dividends declared ($0.18 per common share)	(14,033)			(14,033)
Restricted stock activity	(2,456)		(9,663)			7,207
Restricted stock activity (in Shares)		268
Treasury stock issued to benefit plans	105		(64)			169
Share-based compensation expense	3,487		3,487
Treasury stock issued to benefit plans (in Shares)		(2)
Balance Ending at Jun. 30, 2015	1,124,957	$ 882	443,558	927,939	(21,232)	(226,190)
Balance Ending (in Shares) at Jun. 30, 2015		77,961
Balance Beginning at Dec. 31, 2015	$ 1,146,268	$ 882	446,672	953,516	(28,389)	(226,413)
Balance Beginning (in Shares) at Dec. 31, 2015	77,952	77,952
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 43,229			43,229
Other comprehensive income	19,586				19,586
Common dividends declared ($0.18 per common share)	(14,468)			(14,468)
Acquisition, net of issuance costs	54,896	$ 31	54,865
Acquisition, net of issuance costs (in Shares)		3,042
Common stock issued	112		112
Common stock issued (in Shares)		7
Restricted stock activity	(2,500)		(10,319)			7,819
Restricted stock activity (in Shares)		316
Treasury stock issued to benefit plans	(71)		(8)			(63)
Share-based compensation expense	3,837		3,837
Treasury stock issued to benefit plans (in Shares)		(5)
Balance Ending at Jun. 30, 2016	$ 1,250,889	$ 913	$ 495,159	$ 982,277	$ (8,803)	$ (218,657)
Balance Ending (in Shares) at Jun. 30, 2016	81,312	81,312