Loans and Allowance for Loan Losses - Changes in allowance (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Changes in the allowance
Beginning Balance	$ 27,019	$ 22,638	$ 23,924	$ 22,174
Provision for loan losses	3,500	1,797	6,000	4,017
Loan charge-offs	(3,666)	(3,620)	(3,765)	(5,568)
Loan recoveries	403	431	1,097	623
Ending Balance	27,256	21,246	27,256	21,246
Unallocated
Changes in the allowance
Beginning Balance	1,833	9	2,192	1,177
Provision for loan losses	(86)	1,210	(445)	42
Ending Balance	1,747	1,219	1,747	1,219
Commercial
Changes in the allowance
Beginning Balance	21,511	19,909	19,261	18,656
Provision for loan losses	2,924	660	4,613	3,633
Loan charge-offs	(3,568)	(3,166)	(3,600)	(4,952)
Loan recoveries	321	379	914	445
Ending Balance	21,188	17,782	21,188	17,782
Commercial \| Commercial and industrial
Changes in the allowance
Beginning Balance	12,901	13,815	12,270	12,127
Provision for loan losses	278	818	348	4,225
Loan charge-offs	(2,703)	(3,166)	(2,735)	(4,951)
Loan recoveries	321	227	914	293
Ending Balance	10,797	11,694	10,797	11,694
Commercial \| Real estate construction
Changes in the allowance
Beginning Balance	334	251	303	250
Provision for loan losses	109	70	140	72
Loan charge-offs				(1)
Loan recoveries		2		2
Ending Balance	443	323	443	323
Commercial \| Commercial real estate
Changes in the allowance
Beginning Balance	8,276	5,843	6,688	6,279
Provision for loan losses	2,537	(228)	4,125	(664)
Loan charge-offs	(865)		(865)
Loan recoveries		150		150
Ending Balance	9,948	5,765	9,948	5,765
Consumer
Changes in the allowance
Beginning Balance	3,675	2,720	2,471	2,341
Provision for loan losses	662	(73)	1,832	342
Loan charge-offs	(98)	(454)	(165)	(616)
Loan recoveries	82	52	183	178
Ending Balance	4,321	2,245	4,321	2,245
Consumer \| Residential \| Real estate first mortgage
Changes in the allowance
Beginning Balance	2,209	1,610	1,448	1,156
Provision for loan losses	459	(455)	1,220	(1)
Loan recoveries	5		5
Ending Balance	2,673	1,155	2,673	1,155
Consumer \| Residential \| Real estate junior lien
Changes in the allowance
Beginning Balance	1,025	761	671	805
Provision for loan losses	32	(51)	349	(44)
Loan charge-offs	(12)	(30)	(12)	(134)
Loan recoveries	57	30	94	83
Ending Balance	1,102	710	1,102	710
Consumer \| Other revolving and installment
Changes in the allowance
Beginning Balance	441	349	352	380
Provision for loan losses	171	433	263	387
Loan charge-offs	(86)	(424)	(153)	(482)
Loan recoveries	20	22	84	95
Ending Balance	$ 546	$ 380	$ 546	$ 380

Amount of increase in allowance for credit loss on accounts receivable, from recovery.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
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- Definition

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

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 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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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Amount of expense related loan transactions, lease transactions, credit loss from transactions other than loan and lease transactions, and other loss based on assessment of uncollectability from the counterparty to reduce the account to their net realizable value.

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