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 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
Balances at Jun. 30, 2017	0	308,343,000	50,012,000	(856,000)	357,499,000
Balances at Dec. 31, 2017	0	309,772,000	61,001,000	(4,903,000)	365,870,000
Reclassification of equity securities related to ASU 2016-01 adoption at Dec. 31, 2017			(42,000)	42,000	0
Employee stock purchase plan		26,000			26,000
Dividend reinvestment plan		328,000			328,000
Stock option exercises		55,000			55,000
Stock grants to directors for retainer fees		403,000			403,000
Stock-based compensation expense		1,136,000			1,136,000
Cash dividends			(7,202,000)		(7,202,000)
Net income			20,327,000		20,327,000
Change in net unrealized holding gain/(loss) on securities available for sale, net of tax effect				(6,025,000)	(6,025,000)
Change in fair value of interest rate swap, net of tax effect				1,000	1,000
Balances at Jun. 30, 2018	$ 0	$ 311,720,000	$ 74,084,000	$ (10,885,000)	$ 374,919,000