Condensed Consolidated Statements of Changes in Shareholders' Equity (Unaudited) - USD ($)	Preferred Stock [Member]	Common Stock [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Total
Begining Balances at Dec. 31, 2014	$ 0	$ 317,904,000	$ 10,218,000	$ 16,000	$ 328,138,000
Employee stock purchase plan		33,000			33,000
Dividend reinvestment plan		456,000			456,000
Stock option exercises		281,000			281,000
Stock grants to directors for retainer fees		402,000			402,000
Stock-based compensation expense		525,000			525,000
Share repurchase program		(15,223,000)			(15,223,000)
Cash dividends			(7,085,000)		(7,085,000)
Net income			20,540,000		20,540,000
Change in net unrealized holding gain on securities available for sale, net of tax effect				934,000	934,000
Change in fair value of interest rate swap, net of tax effect				(181,000)	(181,000)
Ending Balance at Sep. 30, 2015	0	304,378,000	23,673,000	769,000	328,820,000
Begining Balances at Dec. 31, 2015	0	304,819,000	27,722,000	1,263,000	333,804,000
Employee stock purchase plan		27,000			27,000
Dividend reinvestment plan		1,079,000			1,079,000
Stock option exercises		606,000			606,000
Stock grants to directors for retainer fees		327,000			327,000
Stock-based compensation expense		901,000			901,000
Share repurchase program		(3,732,000)			(3,732,000)
Cash dividends			(7,895,000)		(7,895,000)
Net income			23,828,000		23,828,000
Change in net unrealized holding gain on securities available for sale, net of tax effect				469,000	469,000
Change in fair value of interest rate swap, net of tax effect				57,000	57,000
Ending Balance at Sep. 30, 2016	$ 0	$ 304,027,000	$ 43,655,000	$ 1,789,000	$ 349,471,000