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, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	$ 11,471	$ 11,472	$ 11,232	$ 10,729	$ 10,729
Charge offs	62	223	542	596	1,273
Recoveries	106	100	200	216	276
Provision for loan losses	250	333	875	1,333	1,500
Ending balance	11,765	11,682	11,765	11,682	11,232
Ending balance specifically evaluated for impairment	2,060	2,402	2,060	2,402	2,308
Ending balance collectively evaluated for impairment	9,705	9,280	9,705	9,280	8,924
Total	1,263,459	1,243,558	1,263,459	1,243,558	1,238,283
Ending balance specifically evaluated for impairment	32,209	32,098	32,209	32,098	31,751
Ending balance collectively evaluated for impairment	1,231,250	1,211,460	1,231,250	1,211,460	1,206,532
Commercial \| Real estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	3,609	3,732	3,567	3,872	3,872
Charge offs	0	0	53	0	168
Recoveries	2	52	15	52	52
Provision for loan losses	184	(195)	266	(335)	(189)
Ending balance	3,795	3,589	3,795	3,589	3,567
Ending balance specifically evaluated for impairment	258	265	258	265	260
Ending balance collectively evaluated for impairment	3,537	3,324	3,537	3,324	3,307
Total	368,165	366,390	368,165	366,390	353,243
Ending balance specifically evaluated for impairment	9,049	9,410	9,049	9,410	9,760
Ending balance collectively evaluated for impairment	359,116	356,980	359,116	356,980	343,483
Commercial \| Construction
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	309	399	255	434	434
Charge offs	0	0	0	0	0
Recoveries	0	0	0	0	0
Provision for loan losses	44	(185)	98	(220)	(179)
Ending balance	353	214	353	214	255
Ending balance specifically evaluated for impairment	0	0	0	0	0
Ending balance collectively evaluated for impairment	353	214	353	214	255
Total	37,242	23,889	37,242	23,889	27,304
Ending balance specifically evaluated for impairment	978	741	978	741	721
Ending balance collectively evaluated for impairment	36,264	23,148	36,264	23,148	26,583
Commercial \| Other
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	3,281	3,475	3,541	3,358	3,358
Charge offs	14	51	123	68	423
Recoveries	68	23	70	33	40
Provision for loan losses	(115)	144	(268)	268	566
Ending balance	3,220	3,591	3,220	3,591	3,541
Ending balance specifically evaluated for impairment	1,275	1,890	1,275	1,890	1,696
Ending balance collectively evaluated for impairment	1,945	1,701	1,945	1,701	1,845
Total	201,859	188,128	201,859	188,128	196,391
Ending balance specifically evaluated for impairment	7,332	9,849	7,332	9,849	9,259
Ending balance collectively evaluated for impairment	194,527	178,279	194,527	178,279	187,132
Municipal
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	25	21	24	20	20
Charge offs	0	0	0	0	0
Recoveries	0	0	0	0	0
Provision for loan losses	1	2	2	3	4
Ending balance	26	23	26	23	24
Ending balance specifically evaluated for impairment	0	0	0	0	0
Ending balance collectively evaluated for impairment	26	23	26	23	24
Total	36,522	56,704	36,522	56,704	51,128
Ending balance specifically evaluated for impairment	0	0	0	0	0
Ending balance collectively evaluated for impairment	36,522	56,704	36,522	56,704	51,128
Residential \| Construction
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	23	29	34	36	36
Charge offs	0	0	0	0	0
Recoveries	0	0	0	0	0
Provision for loan losses	0	7	(11)	0	(2)
Ending balance	23	36	23	36	34
Ending balance specifically evaluated for impairment	0	0	0	0	0
Ending balance collectively evaluated for impairment	23	36	23	36	34
Total	14,118	18,166	14,118	18,166	17,743
Ending balance specifically evaluated for impairment	0	0	0	0	0
Ending balance collectively evaluated for impairment	14,118	18,166	14,118	18,166	17,743
Residential \| Term
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	1,106	1,138	1,235	1,130	1,130
Charge offs	0	116	93	212	213
Recoveries	4	3	10	45	64
Provision for loan losses	27	67	(15)	129	254
Ending balance	1,137	1,092	1,137	1,092	1,235
Ending balance specifically evaluated for impairment	337	238	337	238	335
Ending balance collectively evaluated for impairment	800	854	800	854	900
Total	485,490	459,449	485,490	459,449	469,145
Ending balance specifically evaluated for impairment	13,446	10,928	13,446	10,928	10,904
Ending balance collectively evaluated for impairment	472,044	448,521	472,044	448,521	458,241
Home equity line of credit
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	633	678	730	692	692
Charge offs	0	6	38	121	121
Recoveries	1	0	3	13	24
Provision for loan losses	190	47	129	135	135
Ending balance	824	719	824	719	730
Ending balance specifically evaluated for impairment	184	7	184	7	17
Ending balance collectively evaluated for impairment	640	712	640	712	713
Total	94,144	105,213	94,144	105,213	98,469
Ending balance specifically evaluated for impairment	1,398	1,168	1,398	1,168	1,092
Ending balance collectively evaluated for impairment	92,746	104,045	92,746	104,045	97,377
Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	649	575	630	545	545
Charge offs	48	50	235	195	348
Recoveries	31	22	102	73	96
Provision for loan losses	48	193	183	317	337
Ending balance	680	740	680	740	630
Ending balance specifically evaluated for impairment	6	2	6	2	0
Ending balance collectively evaluated for impairment	674	738	674	738	630
Total	25,919	25,619	25,919	25,619	24,860
Ending balance specifically evaluated for impairment	6	2	6	2	15
Ending balance collectively evaluated for impairment	25,913	25,617	25,913	25,617	24,845
Unallocated
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	1,836	1,425	1,216	642	642
Charge offs	0	0	0	0	0
Recoveries	0	0	0	0	0
Provision for loan losses	(129)	253	491	1,036	574
Ending balance	1,707	1,678	1,707	1,678	1,216
Ending balance specifically evaluated for impairment	0	0	0	0	0
Ending balance collectively evaluated for impairment	1,707	1,678	1,707	1,678	1,216
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

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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- Definition

Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

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

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