Loans and Allowance for Loan Losses - Changes in allowance (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Changes in the allowance
Beginning Balance	$ 27,256	$ 21,246	$ 23,924	$ 22,174
Provision for loan losses	3,500	1,498	9,500	5,515
Loan charge-offs	(51)	(375)	(3,816)	(5,943)
Loan recoveries	632	615	1,729	1,238
Ending Balance	31,337	22,984	31,337	22,984
Unallocated
Changes in the allowance
Beginning Balance	1,747	1,219	2,192	1,177
Provision for loan losses	648	2,420	203	2,462
Ending Balance	2,395	3,639	2,395	3,639
Commercial
Changes in the allowance
Beginning Balance	21,188	17,782	19,261	18,656
Provision for loan losses	1,022	(941)	5,635	2,692
Loan charge-offs	(10)	(324)	(3,610)	(5,276)
Loan recoveries	527	538	1,441	983
Ending Balance	22,727	17,055	22,727	17,055
Commercial \| Commercial and industrial
Changes in the allowance
Beginning Balance	10,797	11,694	12,270	12,127
Provision for loan losses	(846)	(962)	(498)	3,263
Loan charge-offs	(10)	(324)	(2,745)	(5,275)
Loan recoveries	432	538	1,346	831
Ending Balance	10,373	10,946	10,373	10,946
Commercial \| Real estate construction
Changes in the allowance
Beginning Balance	443	323	303	250
Provision for loan losses	40	25	180	97
Loan charge-offs				(1)
Loan recoveries				2
Ending Balance	483	348	483	348
Commercial \| Commercial real estate
Changes in the allowance
Beginning Balance	9,948	5,765	6,688	6,279
Provision for loan losses	1,828	(4)	5,953	(668)
Loan charge-offs			(865)
Loan recoveries	95		95	150
Ending Balance	11,871	5,761	11,871	5,761
Consumer
Changes in the allowance
Beginning Balance	4,321	2,245	2,471	2,341
Provision for loan losses	1,830	19	3,662	361
Loan charge-offs	(41)	(51)	(206)	(667)
Loan recoveries	105	77	288	255
Ending Balance	6,215	2,290	6,215	2,290
Consumer \| Residential \| Real estate first mortgage
Changes in the allowance
Beginning Balance	2,673	1,155	1,448	1,156
Provision for loan losses	1,694	(139)	2,914	(140)
Loan recoveries			5
Ending Balance	4,367	1,016	4,367	1,016
Consumer \| Residential \| Real estate junior lien
Changes in the allowance
Beginning Balance	1,102	710	671	805
Provision for loan losses	28	157	377	113
Loan charge-offs		(20)	(12)	(154)
Loan recoveries	81	49	175	132
Ending Balance	1,211	896	1,211	896
Consumer \| Other revolving and installment
Changes in the allowance
Beginning Balance	546	380	352	380
Provision for loan losses	108	1	371	388
Loan charge-offs	(41)	(31)	(194)	(513)
Loan recoveries	24	28	108	123
Ending Balance	$ 637	$ 378	$ 637	$ 378

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
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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
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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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