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		36,000			36,000
Dividend reinvestment plan		1,426,000			1,426,000
Stock option exercises		289,000			289,000
Stock grants to directors for retainer fees		363,000			363,000
Stock-based compensation expense		1,431,000			1,431,000
Cash dividends			(8,941,000)		(8,941,000)
Net income			23,295,000		23,295,000
Change in net unrealized holding gain/(loss) on securities available for sale, net of tax effect				3,791,000	3,791,000
Change in fair value of interest rate swap, net of tax effect				45,000	45,000
Balances at Sep. 30, 2017	0	309,033,000	55,258,000	(1,745,000)	362,546,000
Balances at Dec. 31, 2017	0	309,772,000	61,001,000	(4,903,000)	365,870,000
Employee stock purchase plan		40,000			40,000
Dividend reinvestment plan		500,000			500,000
Stock option exercises		66,000			66,000
Stock grants to directors for retainer fees		403,000			403,000
Stock-based compensation expense		1,763,000			1,763,000
Cash dividends			(11,134,000)		(11,134,000)
Net income			30,450,000		30,450,000
Reclassification of equity securities related to ASU 2016-01 adoption at Dec. 31, 2017			(42,000)	42,000	0
Change in net unrealized holding gain/(loss) on securities available for sale, net of tax effect				(8,494,000)	(8,494,000)
Change in fair value of interest rate swap, net of tax effect				1,000	1,000
Balances at Sep. 30, 2018	$ 0	$ 312,544,000	$ 80,275,000	$ (13,354,000)	$ 379,465,000