Consolidated Statements of Changes in Stockholders’ Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Treasury Stock
Balance at Beginning at Dec. 31, 2013	$ 1,001,442	$ 858	$ 414,293	$ 853,740	$ (26,792)	$ (240,657)
Balance at Beginning (in shares) at Dec. 31, 2013		75,071
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	69,306			69,306
Other comprehensive income (loss)	10,937				10,937
Common dividends declared ($0.31, $0.36 and $0.36)	(23,530)			(23,530)
Acquisition, net of issuance costs	38,300	$ 24	38,276
Acquisition, net of issuance costs (in shares)		2,441
Restricted stock activity	(1,975)		(8,560)			6,585
Restricted stock activity (in shares)		176
Treasury stock issued to benefit plans	369		(137)			506
Treasury stock issued to benefit plans (in shares)		7
Share-based compensation expense	5,926		5,926
Balance at Ending at Dec. 31, 2014	1,100,775	$ 882	449,798	899,516	(15,855)	(233,566)
Balance at Ending (in shares) at Dec. 31, 2014		77,695
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	82,064			82,064
Other comprehensive income (loss)	(12,534)				(12,534)
Common dividends declared ($0.31, $0.36 and $0.36)	(28,064)			(28,064)
Acquisition, net of issuance costs	0
Purchase of treasury stock	(120)					(120)
Purchase of treasury stock (in shares)		(7)
Restricted stock activity	(3,296)		(10,236)			6,940
Restricted stock activity (in shares)		267
Treasury stock issued to benefit plans	201		(132)			333
Treasury stock issued to benefit plans (in shares)		(3)
Share-based compensation expense	7,242		7,242
Balance at Ending at Dec. 31, 2015	$ 1,146,268	$ 882	446,672	953,516	(28,389)	(226,413)
Balance at Ending (in shares) at Dec. 31, 2015	77,952	77,952
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 92,349			92,349
Other comprehensive income (loss)	(12,521)				(12,521)
Common dividends declared ($0.31, $0.36 and $0.36)	(29,191)			(29,191)
Acquisition, net of issuance costs	54,896	$ 31	54,865
Acquisition, net of issuance costs (in shares)		3,042
Common stock issued	227		227
Common stock issued (in shares)		13
Restricted stock activity	(2,673)		(10,685)			8,012
Restricted stock activity (in shares)		326
Treasury stock issued to benefit plans	(154)		(21)			(133)
Treasury stock issued to benefit plans (in shares)		(8)
Share-based compensation expense	7,879		7,879
Balance at Ending at Dec. 31, 2016	$ 1,257,080	$ 913	$ 498,937	$ 1,016,674	$ (40,910)	$ (218,534)
Balance at Ending (in shares) at Dec. 31, 2016	81,325	81,325