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) [Member]
Common Stock, Shares Outstanding, Beginning Balance at Dec. 31, 2013		16,614,000
Shareholders' Equity, Beginning Balance at Dec. 31, 2013	$ 329,646	$ 1,038	$ 97,566	$ 232,595	$ (1,553)
Net income	19,095			19,095
Total other comprehensive (loss) income, net of tax	2,753				2,753
Cash dividends declared	(9,772)			(9,772)
Share-based compensation	961		961
Exercise of stock options, issuance of other compensation-related equity instruments and related tax benefit, shares		91,000
Exercise of stock options, issuance of other compensation-related equity instruments and related tax benefit	767	$ 6	761
Common Stock, Shares Outstanding, Ending Balance at Jun. 30, 2014		16,705,000
Shareholders' Equity, Ending Balance at Jun. 30, 2014	$ 343,450	$ 1,044	99,288	241,918	1,200
Common Stock, Shares Outstanding, Beginning Balance at Dec. 31, 2014	16,746,363	16,746,000
Shareholders' Equity, Beginning Balance at Dec. 31, 2014	$ 346,279	$ 1,047	101,204	252,837	(8,809)
Net income	22,513			22,513
Total other comprehensive (loss) income, net of tax	(274)				(274)
Cash dividends declared	(11,560)			(11,560)
Share-based compensation	1,156		1,156
Exercise of stock options, issuance of other compensation-related equity instruments and related tax benefit, shares		88,000
Exercise of stock options, issuance of other compensation-related equity instruments and related tax benefit	$ 1,053	$ 5	1,048
Common Stock, Shares Outstanding, Ending Balance at Jun. 30, 2015	16,833,525	16,834,000
Shareholders' Equity, Ending Balance at Jun. 30, 2015	$ 359,167	$ 1,052	$ 103,408	$ 263,790	$ (9,083)