Condensed Financial Information of Parent (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Assets
Goodwill	$ 30,646				$ 30,646				$ 30,646	$ 30,646
Other assets	43,714				54,873				43,714	54,873
Total assets	2,527,099	$ 2,529,591	$ 2,450,443	$ 2,436,868	2,361,236	$ 2,296,626	$ 2,267,124	$ 2,136,396	2,527,099	2,361,236
Liabilities and shareholders' equity
Other liabilities	21,803	24,440	26,319	25,479	30,861	30,340	31,614	28,487	21,803	30,861
Total liabilities	2,281,442				2,137,510				2,281,442	2,137,510
Shareholders' equity
Common stock	110				110				110	110
Additional paid-in capital	66,830				65,285				66,830	65,285
Retained earnings	180,417				158,359				180,417	158,359
Total shareholders' equity	245,657	238,737	234,155	228,184	223,726	219,440	216,584	215,257	245,657	223,726	$ 212,508	$ 191,542
Total liabilities and shareholders' equity	2,527,099	2,529,591	2,450,443	2,436,868	2,361,236	2,296,626	2,267,124	2,136,396	2,527,099	2,361,236
Statements of Income
Net securities gains									23	1,155	224
Applicable tax expense	2,053	1,915	1,826	1,850	1,285	1,379	1,256	1,201	7,644	5,121	4,735
Equity in earnings of Bank
Net income	9,546	9,014	8,787	8,922	6,970	7,095	6,569	6,495	36,269	27,129	25,525
Cash flows from operating activities
Net income	9,546	9,014	8,787	8,922	6,970	7,095	6,569	6,495	36,269	27,129	25,525
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation									2,039	2,221	1,938
Equity compensation expense									856	652	565
Gain on sale of investments									(23)	(1,155)	(224)
Increase in other assets									18,604	(17,737)	(7,690)
Increase (decrease) in other liabilities									(9,332)	9,347	2,802
Net cash provided by operating activities									56,693	22,698	26,053
Cash flows from financing activities
Purchase of common stock									(253)	(156)	(183)
Proceeds from sale of common stock									689	670	653
Dividends paid									(13,948)	(13,329)	(12,963)
Net cash provided by financing activities									139,478	239,152	85,526
Net increase (decrease) in cash and cash equivalents									(5,578)	11,779	(4,701)
Cash and cash equivalents at beginning of year	27,126	27,092	20,029	26,212	22,742	22,143	21,117	14,433	26,212	14,433	19,134
Cash and cash equivalents at end of year	20,634	$ 27,126	$ 27,092	20,029	26,212	$ 22,742	$ 22,143	21,117	20,634	26,212	14,433
Parent Company
Assets
Cash and cash equivalents	1,401				1,287				1,401	1,287
Dividends receivable	3,200				3,400				3,200	3,400
Investment in subsidiary	216,591				194,515				216,591	194,515
Goodwill	27,559				27,559				27,559	27,559
Other assets	431				360				431	360
Total assets	249,182				227,121				249,182	227,121
Liabilities and shareholders' equity
Dividends payable	3,520				3,395				3,520	3,395
Other liabilities	5				0				5	0
Total liabilities	3,525				3,395				3,525	3,395
Shareholders' equity
Common stock	110				110				110	110
Additional paid-in capital	66,830				65,285				66,830	65,285
Retained earnings	178,717				158,331				178,717	158,331
Total shareholders' equity	245,657				223,726				245,657	223,726
Total liabilities and shareholders' equity	249,182				227,121				249,182	227,121
Statements of Income
Net securities gains									0	0	0
Other operating income									0	8	0
Total income									0	8	0
Occupancy expense									0	0	1
Other operating expense									1,148	911	826
Total expense									1,148	911	827
Income before income taxes									(1,148)	(903)	(827)
Applicable tax expense									(269)	(246)	(230)
Loss before Bank earnings									(879)	(657)	(597)
Equity in earnings of Bank
Remitted									13,400	13,300	12,600
Unremitted									23,748	14,486	13,522
Net income									36,269	27,129	25,525
Cash flows from operating activities
Net income									36,269	27,129	25,525
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation									0	0	2
Equity compensation expense									856	652	565
Gain on sale of investments									0	0	0
Increase in other assets									(71)	(21)	(105)
(Increase) decrease in dividends receivable									200	(200)	(250)
Increase in dividends payable									115	0	120
Increase (decrease) in other liabilities									5	0	(4)
Unremitted earnings of Bank									(23,748)	(14,486)	(13,522)
Net cash provided by operating activities									13,626	13,074	12,331
Cash flows from financing activities
Purchase of common stock									(253)	(156)	(183)
Proceeds from sale of common stock									689	670	653
Dividends paid									(13,948)	(13,329)	(12,963)
Net cash provided by financing activities									(13,512)	(12,815)	(12,493)
Net increase (decrease) in cash and cash equivalents									114	259	(162)
Cash and cash equivalents at beginning of year				$ 1,287				$ 1,028	1,287	1,028	1,190
Cash and cash equivalents at end of year	$ 1,401				$ 1,287				$ 1,401	$ 1,287	$ 1,028