Allowance for Loan Losses - Allowance for Loan Loss Activity by Class (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	$ 14,110	$ 11,471	$ 11,639	$ 11,232	$ 11,232
Charge offs	576	62	993	542	1,120
Recoveries	37	106	175	200	277
Provision (credit)	1,800	250	4,550	875	1,250
Ending balance	15,371	11,765	15,371	11,765	11,639
Ending balance specifically evaluated for impairment	890	2,060	890	2,060	2,213
Ending balance collectively evaluated for impairment	14,481	9,705	14,481	9,705	9,426
Total	1,436,646	1,263,459	1,436,646	1,263,459	1,297,075
Ending balance specifically evaluated for impairment	19,341	32,209	19,341	32,209	29,274
Ending balance collectively evaluated for impairment	1,417,305	1,231,250	1,417,305	1,231,250	1,267,801
Commercial \| Real estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	4,511	3,609	3,742	3,567	3,567
Charge offs	532	0	532	53	89
Recoveries	0	2	0	15	15
Provision (credit)	782	184	1,551	266	249
Ending balance	4,761	3,795	4,761	3,795	3,742
Ending balance specifically evaluated for impairment	135	258	135	258	251
Ending balance collectively evaluated for impairment	4,626	3,537	4,626	3,537	3,491
Total	407,128	368,165	407,128	368,165	372,810
Ending balance specifically evaluated for impairment	4,753	9,049	4,753	9,049	6,309
Ending balance collectively evaluated for impairment	402,375	359,116	402,375	359,116	366,501
Commercial \| Construction
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	524	309	365	255	255
Charge offs	0	0	0	0	0
Recoveries	0	0	0	0	0
Provision (credit)	83	44	242	98	110
Ending balance	607	353	607	353	365
Ending balance specifically evaluated for impairment	19	0	19	0	0
Ending balance collectively evaluated for impairment	588	353	588	353	365
Total	52,038	37,242	52,038	37,242	38,084
Ending balance specifically evaluated for impairment	1,009	978	1,009	978	958
Ending balance collectively evaluated for impairment	51,029	36,264	51,029	36,264	37,126
Commercial \| Other
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	3,689	3,281	3,329	3,541	3,541
Charge offs	7	14	24	123	179
Recoveries	4	68	24	70	73
Provision (credit)	(44)	(115)	313	(268)	(106)
Ending balance	3,642	3,220	3,642	3,220	3,329
Ending balance specifically evaluated for impairment	128	1,275	128	1,275	1,273
Ending balance collectively evaluated for impairment	3,514	1,945	3,514	1,945	2,056
Total	309,297	201,859	309,297	201,859	218,773
Ending balance specifically evaluated for impairment	1,023	7,332	1,023	7,332	7,075
Ending balance collectively evaluated for impairment	308,274	194,527	308,274	194,527	211,698
Municipal
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	110	25	27	24	24
Charge offs	0	0	0	0	0
Recoveries	0	0	0	0	0
Provision (credit)	29	1	112	2	3
Ending balance	139	26	139	26	27
Ending balance specifically evaluated for impairment	0	0	0	0	0
Ending balance collectively evaluated for impairment	139	26	139	26	27
Total	44,110	36,522	44,110	36,522	41,288
Ending balance specifically evaluated for impairment	0	0	0	0	0
Ending balance collectively evaluated for impairment	44,110	36,522	44,110	36,522	41,288
Residential \| Construction
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	64	23	25	34	34
Charge offs	0	0	0	0	0
Recoveries	0	0	0	0	0
Provision (credit)	17	0	56	(11)	(9)
Ending balance	81	23	81	23	25
Ending balance specifically evaluated for impairment	0	0	0	0	0
Ending balance collectively evaluated for impairment	81	23	81	23	25
Total	16,101	14,118	16,101	14,118	14,813
Ending balance specifically evaluated for impairment	0	0	0	0	0
Ending balance collectively evaluated for impairment	16,101	14,118	16,101	14,118	14,813
Residential \| Term
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	2,261	1,106	1,024	1,235	1,235
Charge offs	0	0	46	93	445
Recoveries	5	4	31	10	57
Provision (credit)	250	27	1,507	(15)	177
Ending balance	2,516	1,137	2,516	1,137	1,024
Ending balance specifically evaluated for impairment	204	337	204	337	237
Ending balance collectively evaluated for impairment	2,312	800	2,312	800	787
Total	497,667	485,490	497,667	485,490	492,455
Ending balance specifically evaluated for impairment	10,182	13,446	10,182	13,446	12,439
Ending balance collectively evaluated for impairment	487,485	472,044	487,485	472,044	480,016
Home equity line of credit
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	1,284	633	1,078	730	730
Charge offs	0	0	153	38	69
Recoveries	1	1	20	3	4
Provision (credit)	172	190	512	129	413
Ending balance	1,457	824	1,457	824	1,078
Ending balance specifically evaluated for impairment	403	184	403	184	447
Ending balance collectively evaluated for impairment	1,054	640	1,054	640	631
Total	82,982	94,144	82,982	94,144	92,349
Ending balance specifically evaluated for impairment	2,364	1,398	2,364	1,398	2,488
Ending balance collectively evaluated for impairment	80,618	92,746	80,618	92,746	89,861
Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	658	649	867	630	630
Charge offs	37	48	238	235	338
Recoveries	27	31	100	102	128
Provision (credit)	(56)	48	(137)	183	447
Ending balance	592	680	592	680	867
Ending balance specifically evaluated for impairment	1	6	1	6	5
Ending balance collectively evaluated for impairment	591	674	591	674	862
Total	27,323	25,919	27,323	25,919	26,503
Ending balance specifically evaluated for impairment	10	6	10	6	5
Ending balance collectively evaluated for impairment	27,313	25,913	27,313	25,913	26,498
Unallocated
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	1,009	1,836	1,182	1,216	1,216
Charge offs	0	0	0	0	0
Recoveries	0	0	0	0	0
Provision (credit)	567	(129)	394	491	(34)
Ending balance	1,576	1,707	1,576	1,707	1,182
Ending balance specifically evaluated for impairment	0	0	0	0	0
Ending balance collectively evaluated for impairment	1,576	1,707	1,576	1,707	1,182
Total	0	0	0	0	0
Ending balance specifically evaluated for impairment	0	0	0	0	0
Ending balance collectively evaluated for impairment	$ 0	$ 0	$ 0	$ 0	$ 0

Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

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- Definition

Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

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The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

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Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

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The balance of financing receivables that were collectively evaluated for impairment.

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Amount, before allowance for credit loss, of financing receivable.

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Amount of expense related to estimated loss from loan and lease transactions.

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