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		12,000			12,000
Dividend reinvestment plan		1,145,000			1,145,000
Stock option exercises		248,000			248,000
Stock grant for director fees		2,000			2,000
Stock-based compensation expense		476,000			476,000
Cash dividends			(2,923,000)		(2,923,000)
Net income			7,615,000		7,615,000
Change in net unrealized holding gain/(loss) on securities available for sale, net of tax effect				637,000	637,000
Change in fair value of interest rate swap, net of tax effect				27,000	27,000
Balances at Mar. 31, 2017	0	307,371,000	45,596,000	(4,917,000)	348,050,000
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		14,000			14,000
Dividend reinvestment plan		164,000			164,000
Stock option exercises		54,000			54,000
Stock-based compensation expense		597,000			597,000
Cash dividends			(3,599,000)		(3,599,000)
Net income			10,881,000		10,881,000
Change in net unrealized holding gain/(loss) on securities available for sale, net of tax effect				(5,642,000)	(5,642,000)
Change in fair value of interest rate swap, net of tax effect				1,000	1,000
Balances at Mar. 31, 2018	$ 0	$ 310,601,000	$ 68,241,000	$ (10,502,000)	$ 368,340,000