Allowance for Loan Losses - Allowance for Loan Loss Activity by Class (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	$ 11,639	$ 11,232	$ 11,232
Charge offs	255	151	1,120
Recoveries	74	34	277
Provision (credit)	400	375	1,250
Ending balance	11,858	11,490	11,639
Ending balance specifically evaluated for impairment	992	2,075	2,213
Ending balance collectively evaluated for impairment	10,866	9,415	9,426
Total	1,344,208	1,264,639	1,297,075
Ending balance specifically evaluated for impairment	22,493	30,568	29,274
Ending balance collectively evaluated for impairment	1,321,715	1,234,071	1,267,801
Commercial \| Real estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	3,742	3,567	3,567
Charge offs	0	0	89
Recoveries	0	8	15
Provision (credit)	120	57	249
Ending balance	3,862	3,632	3,742
Ending balance specifically evaluated for impairment	230	233	251
Ending balance collectively evaluated for impairment	3,632	3,399	3,491
Total	382,753	357,760	372,810
Ending balance specifically evaluated for impairment	6,223	9,957	6,309
Ending balance collectively evaluated for impairment	376,530	347,803	366,501
Commercial \| Construction
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	365	255	255
Charge offs	0	0	0
Recoveries	0	0	0
Provision (credit)	59	70	110
Ending balance	424	325	365
Ending balance specifically evaluated for impairment	3	0	0
Ending balance collectively evaluated for impairment	421	325	365
Total	43,913	34,231	38,084
Ending balance specifically evaluated for impairment	947	1,007	958
Ending balance collectively evaluated for impairment	42,966	33,224	37,126
Commercial \| Other
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	3,329	3,541	3,541
Charge offs	0	1	179
Recoveries	20	1	73
Provision (credit)	(922)	(111)	(106)
Ending balance	2,427	3,430	3,329
Ending balance specifically evaluated for impairment	172	1,485	1,273
Ending balance collectively evaluated for impairment	2,255	1,945	2,056
Total	237,896	205,462	218,773
Ending balance specifically evaluated for impairment	990	7,653	7,075
Ending balance collectively evaluated for impairment	236,906	197,809	211,698
Municipal
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	27	24	24
Charge offs	0	0	0
Recoveries	0	0	0
Provision (credit)	2	1	3
Ending balance	29	25	27
Ending balance specifically evaluated for impairment	0	0	0
Ending balance collectively evaluated for impairment	29	25	27
Total	43,537	54,246	41,288
Ending balance specifically evaluated for impairment	0	0	0
Ending balance collectively evaluated for impairment	43,537	54,246	41,288
Residential \| Construction
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	25	34	34
Charge offs	0	0	0
Recoveries	0	0	0
Provision (credit)	7	(4)	(9)
Ending balance	32	30	25
Ending balance specifically evaluated for impairment	0	0	0
Ending balance collectively evaluated for impairment	32	30	25
Total	15,202	18,450	14,813
Ending balance specifically evaluated for impairment	0	0	0
Ending balance collectively evaluated for impairment	15,202	18,450	14,813
Residential \| Term
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	1,024	1,235	1,235
Charge offs	2	49	445
Recoveries	10	3	57
Provision (credit)	194	(75)	177
Ending balance	1,226	1,114	1,024
Ending balance specifically evaluated for impairment	233	348	237
Ending balance collectively evaluated for impairment	993	766	787
Total	500,971	474,241	492,455
Ending balance specifically evaluated for impairment	12,038	10,919	12,439
Ending balance collectively evaluated for impairment	488,933	463,322	480,016
Home equity line of credit
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	1,078	730	730
Charge offs	153	38	69
Recoveries	1	1	4
Provision (credit)	86	(63)	413
Ending balance	1,012	630	1,078
Ending balance specifically evaluated for impairment	296	7	447
Ending balance collectively evaluated for impairment	716	623	631
Total	90,674	95,692	92,349
Ending balance specifically evaluated for impairment	2,228	1,030	2,488
Ending balance collectively evaluated for impairment	88,446	94,662	89,861
Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	867	630	630
Charge offs	100	63	338
Recoveries	43	21	128
Provision (credit)	(85)	72	447
Ending balance	725	660	867
Ending balance specifically evaluated for impairment	58	2	5
Ending balance collectively evaluated for impairment	667	658	862
Total	29,262	24,557	26,503
Ending balance specifically evaluated for impairment	67	2	5
Ending balance collectively evaluated for impairment	29,195	24,555	26,498
Unallocated
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	1,182	1,216	1,216
Charge offs	0	0	0
Recoveries	0	0	0
Provision (credit)	939	428	(34)
Ending balance	2,121	1,644	1,182
Ending balance specifically evaluated for impairment	0	0	0
Ending balance collectively evaluated for impairment	2,121	1,644	1,182
Total	0	0	0
Ending balance specifically evaluated for impairment	0	0	0
Ending balance collectively evaluated for impairment	$ 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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- Definition

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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