CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (Unaudited) (USD $) In Thousands, except Share data	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Shareholders' Equity, Beginning Balance at Dec. 31, 2012	$ 295,652	$ 1,024	$ 91,453	$ 213,674	$ (10,499)
Common Stock, Shares Outstanding, Beginning Balance at Dec. 31, 2012		16,380,000
Net income	26,364			26,364
Total other comprehensive income (loss), net of tax	9,159				9,159
Cash dividends declared	(12,686)			(12,686)
Share-based compensation	1,377		1,377
Deferred compensation plan, shares		2,000
Deferred compensation plan	30		30
Exercise of stock options, issuance of other compensation-related equity instruments and related tax benefit, shares		207,000
Exercise of stock options, issuance of other compensation-related equity instruments and related tax benefit	3,689	13	3,676
Shareholders' Equity, Ending Balance at Sep. 30, 2013	323,585	1,037	96,536	227,352	(1,340)
Common Stock, Shares Outstanding, Ending Balance at Sep. 30, 2013		16,589,000
Shareholders' Equity, Beginning Balance at Dec. 31, 2013	329,646	1,038	97,566	232,595	(1,553)
Common Stock, Shares Outstanding, Beginning Balance at Dec. 31, 2013	16,613,561	16,614,000
Net income	29,633			29,633
Total other comprehensive income (loss), net of tax	1,974				1,974
Cash dividends declared	(15,176)			(15,176)
Share-based compensation	1,433		1,433
Exercise of stock options, issuance of other compensation-related equity instruments and related tax benefit, shares		107,000
Exercise of stock options, issuance of other compensation-related equity instruments and related tax benefit	1,052	7	1,045
Shareholders' Equity, Ending Balance at Sep. 30, 2014	$ 348,562	$ 1,045	$ 100,044	$ 247,052	$ 421
Common Stock, Shares Outstanding, Ending Balance at Sep. 30, 2014	16,721,172	16,721,000