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
Balances at Jun. 30, 2016	$ 0	$ 303,336,000	$ 38,553,000	$ 2,688,000	$ 344,577,000
Balances at Dec. 31, 2015	0	304,819,000	27,722,000	1,263,000	333,804,000
Employee stock purchase plan		18,000			18,000
Dividend reinvestment plan		909,000			909,000
Stock option exercises		379,000			379,000
Stock grants to directors for retainer fees		327,000			327,000
Stock-based compensation expense		616,000			616,000
Share repurchase program		(3,732,000)			(3,732,000)
Cash dividends			(5,152,000)		(5,152,000)
Net income			15,983,000		15,983,000
Change in net unrealized holding gain/(loss) on securities available for sale, net of tax effect				1,441,000	1,441,000
Change in fair value of interest rate swap, net of tax effect				(16,000)	(16,000)
Balances at Jun. 30, 2017	0	308,343,000	50,012,000	(856,000)	357,499,000
Balances at Dec. 31, 2016	$ 0	305,488,000	40,904,000	(5,581,000)	340,811,000
Employee stock purchase plan		23,000			23,000
Dividend reinvestment plan		1,286,000			1,286,000
Stock option exercises		248,000			248,000
Stock grants to directors for retainer fees		363,000			363,000
Stock-based compensation expense		$ 935,000			935,000
Cash dividends			(5,850,000)		(5,850,000)
Net income			$ 14,958,000		14,958,000
Change in net unrealized holding gain/(loss) on securities available for sale, net of tax effect				4,688,000	4,688,000
Change in fair value of interest rate swap, net of tax effect				$ 37,000	$ 37,000