CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY - USD ($)		Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive (Loss)/Income	Reclassifications Related to Funded Status of Pension	Reclassifications Related to Unrealized Gains on Available for Sale Securities	Treasury Stock
Beginning Balance at Dec. 31, 2016		$ 841,956,000	$ 90,326,000	$ 213,098,000	$ 585,891,000	$ (13,784,000)			$ (33,575,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		63,674,000			63,674,000
Other comprehensive income, net of tax		1,180,000				1,180,000
Cash dividends declared ($0.72 and $0.60 per share)		(20,899,000)			(20,899,000)
Treasury stock issued for restricted awards (75,608 shares, net of 40,950 forfeitures and 90,115 shares, net of 23,946 forfeitures)		(688,000)			(2,383,000)				1,695,000
Recognition of restricted stock compensation expense		2,353,000		2,353,000
Ending Balance at Sep. 30, 2017		887,576,000	90,326,000	215,451,000	626,283,000	(12,604,000)			(31,880,000)
Effect of new accounting pronouncement on Consolidated Financial Statements | ASU No. 2018-02		0
Effect of new accounting pronouncement on Consolidated Financial Statements | ASU No. 2016-01	[1]				862,000	(862,000)
Beginning Balance at Dec. 31, 2017		884,031,000	90,326,000	216,106,000	628,107,000	(18,427,000)			(32,081,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		78,480,000			78,480,000
Other comprehensive income, net of tax		(10,537,000)				(10,537,000)
Reclassification of tax effects from the Tax Act | ASU No. 2018-02	[2]				3,427,000	(3,427,000)	$ (3,660,000)	$ 233,000
Cash dividends declared ($0.72 and $0.60 per share)		(25,115,000)			(25,115,000)
Treasury stock issued for restricted awards (75,608 shares, net of 40,950 forfeitures and 90,115 shares, net of 23,946 forfeitures)		(657,000)			(1,400,000)				743,000
Repurchase of warrant		(7,652,000)		(7,652,000)
Recognition of restricted stock compensation expense		1,231,000		1,231,000
Ending Balance at Sep. 30, 2018		$ 919,781,000	$ 90,326,000	$ 209,685,000	$ 684,361,000	$ (33,253,000)			$ (31,338,000)

[1] Reclassification due to the adoption of ASU No. 2016-01.

[2] Reclassification due to the adoption of ASU No. 2018-02, $(3,660) relates to funded status of pension and $233 relates to net unrealized gains on available-for-sale securities.