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Loans and Allowance for Loan Losses - Troubled Debt Restructuring by Class (Details)	9 Months Ended	12 Months Ended
	Sep. 30, 2018 loan	Dec. 31, 2018 USD ($) loan	Dec. 31, 2017 USD ($) loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans removed from TDR resignation | loan			0
Recorded investment of loans removed from TDR resignation		$ 247,000
Recorded investment in Troubled Debt Restructurings		14,406,000	$ 16,520,000
Acquired loans included in TDR		$ 0	0
TDR loans on non-accrual status | loan		2
TDR loans on non-accrual status, value		$ 65,000
TDR loans accruing interest as of period end			0
Commercial | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment in Troubled Debt Restructurings		1,506,000	2,165,000
Commercial real estate | Commercial real estate, owner-occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment in Troubled Debt Restructurings		6,993,000	6,999,000
Commercial real estate | Commercial real estate, investor
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment in Troubled Debt Restructurings		1,821,000	2,171,000
Commercial real estate | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment in Troubled Debt Restructurings		2,688,000	2,969,000
Residential loans | Home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans removed from TDR resignation | loan	1
Recorded investment in Troubled Debt Restructurings		$ 251,000	347,000
Residential loans | Other residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans removed from TDR resignation | loan		1
Recorded investment in Troubled Debt Restructurings		$ 462,000	1,148,000
Consumer loans | Installment and other consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment in Troubled Debt Restructurings		$ 685,000	$ 721,000

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=82895541&loc=d3e18845-111554

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