Consolidated Statements of Changes in Shareholders' Equity (Unaudited) - USD ($)	Preferred Stock [Member]	Common Stock Including Additional Paid in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Total
Balances at Dec. 31, 2019	$ 0	$ 305,035,000	$ 107,831,000	$ 3,695,000	$ 416,561,000
Employee stock purchase plan		37,000			37,000
Dividend reinvestment plan		610,000			610,000
Stock-based compensation expense		2,102,000			2,102,000
Share repurchase program		(6,282,000)			(6,282,000)
Cash dividends			(13,436,000)		(13,436,000)
Net income			30,056,000		30,056,000
Change in net unrealized holding gain/(loss) on securities available for sale, net of tax effect				1,858,000	1,858,000
Stock grants to directors for retainer fees		394,000			394,000
Balances at Sep. 30, 2020	0	301,896,000	124,451,000	5,553,000	431,900,000
Balances at Jun. 30, 2020	0	300,897,000	118,239,000	6,085,000	425,221,000
Employee stock purchase plan		12,000			12,000
Dividend reinvestment plan		206,000			206,000
Stock-based compensation expense		736,000			736,000
Cash dividends			(4,474,000)		(4,474,000)
Net income			10,686,000		10,686,000
Change in net unrealized holding gain/(loss) on securities available for sale, net of tax effect				(532,000)	(532,000)
Stock grants to directors for retainer fees		45,000			45,000
Balances at Sep. 30, 2020	0	301,896,000	124,451,000	5,553,000	431,900,000
Balances at Dec. 31, 2020	0	302,029,000	134,039,000	5,486,000	441,554,000
Employee stock purchase plan		35,000			35,000
Dividend reinvestment plan		648,000			648,000
Stock option exercises		50,000			50,000
Stock-based compensation expense		1,725,000			1,725,000
Share repurchase program		(19,798,000)			(19,798,000)
Cash dividends			(13,880,000)		(13,880,000)
Net income			47,382,000		47,382,000
Change in net unrealized holding gain/(loss) on securities available for sale, net of tax effect				(5,782,000)	(5,782,000)
Stock grants to directors for retainer fees		344,000			344,000
Balances at Sep. 30, 2021	0	285,033,000	167,541,000	(296,000)	452,278,000
Balances at Jun. 30, 2021	0	293,232,000	157,150,000	1,506,000	451,888,000
Employee stock purchase plan		13,000			13,000
Dividend reinvestment plan		237,000			237,000
Stock option exercises		50,000			50,000
Stock-based compensation expense		448,000			448,000
Share repurchase program		(8,947,000)			(8,947,000)
Cash dividends			(4,660,000)		(4,660,000)
Net income			15,051,000		15,051,000
Change in net unrealized holding gain/(loss) on securities available for sale, net of tax effect				(1,802,000)	(1,802,000)
Balances at Sep. 30, 2021	$ 0	$ 285,033,000	$ 167,541,000	$ (296,000)	$ 452,278,000