Amount of Loan Portfolio reclassified from spoecial mention ratings to pass rating.

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- Definition

Business lines of credit, maturity period

+ References

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- Definition

Historical loss experience look back period.

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- Definition

Loans And Leases Receivable Period for loan to be Nonaccrual

+ References

No definition available.

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- Definition

Maximum Loan To Value Ratio

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- Definition

Maximum terms offered to loans

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- Definition

Period for loans to be considered for charge off.

+ References

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Number of financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953676-111524

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- Definition

The amount of the outstanding recorded investment related to financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-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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- Definition

Reflects the amount of the write-down related to a troubled debt restructuring.

+ References

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- Definition

Recorded investment of consumer mortgage loan receivables secured by residential real estate properties for which formal foreclosure proceedings are in process.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 35
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL49126937-111524

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Loans and Related Allowance for Credit Losses (Narrative) (Details)	9 Months Ended		12 Months Ended
	Sep. 30, 2018 USD ($) contract	Sep. 30, 2017 USD ($) contract	Dec. 31, 2017 USD ($)	Dec. 31, 2017 USD ($) loan	Dec. 31, 2017 USD ($) contract	Dec. 31, 2017 USD ($)	Dec. 31, 2016	Jun. 30, 2018 USD ($)
Financing Receivable, Allowance for Credit Losses [Line Items]
Period for loan to be nonaccrual	90 days
Business lines of credit, maturity period	5 years
Period for loans to be considered for charge off	120 days
Number of troubled debt restructurings \| contract	9				9
Trouble debt restructured loan	$ 457,000		$ 339,000	$ 339,000	$ 339,000	$ 339,000
Amount of Loan Portfolio reclassified from special mention ratings to pass rating								$ 32,603,000
Historical loss experience look back period			5 years				10 years
Non-Accruing Troubled Debt Restructurings [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Troubled debt restructurings, charge-off						8,000
Home Equity Lines of Credit [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Maximum terms offered to loans	20 years
Maximum loan-to-value ratio	90.00%
Fixed Rate and Adjustable Rate Mortgage Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Maximum terms offered to loans	25 years
Home Equity Installment Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Maximum terms offered to loans	15 years
Maximum loan-to-value ratio	95.00%
Real Estate Portfolio Segment [Member] \| Commercial Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Maximum terms offered to loans	20 years
Maximum loan-to-value ratio	80.00%
Real Estate Portfolio Segment [Member] \| Mortgage Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Maximum loan-to-value ratio	80.00%
Loan balance in the process of foreclosure	$ 990,000		$ 1,285,000	1,285,000	$ 1,285,000	1,285,000
Real Estate Portfolio Segment [Member] \| Mortgage Loan [Member] \| Non-Accruing Troubled Debt Restructurings [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Number of troubled debt restructurings \| contract	1				1
Trouble debt restructured loan	$ 18,000		20,000	20,000	$ 20,000	20,000
Real Estate Portfolio Segment [Member] \| Mortgage Loan [Member] \| Accruing Troubled Debt Restructurings [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Number of troubled debt restructurings \| contract	8				7
Trouble debt restructured loan	$ 439,000		315,000	$ 315,000	$ 315,000	315,000
Commercial Portfolio Segment [Member] \| Commercial, Financial and Agricultural [Member] \| Non-Accruing Troubled Debt Restructurings [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Number of troubled debt restructurings				1	1
Trouble debt restructured loan			$ 4,000	$ 4,000	$ 4,000	$ 4,000
Restructured Loan [Member] \| Accruing Troubled Debt Restructurings [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Number of troubled debt restructurings \| contract	1	1
Trouble debt restructured loan	$ 153,000	$ 7,000
Restructured Loan [Member] \| Real Estate Portfolio Segment [Member] \| Mortgage Loan [Member] \| Accruing Troubled Debt Restructurings [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Number of troubled debt restructurings \| contract	1
Trouble debt restructured loan	$ 153,000
Restructured Loan [Member] \| Commercial Portfolio Segment [Member] \| Commercial, Financial and Agricultural [Member] \| Accruing Troubled Debt Restructurings [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Number of troubled debt restructurings \| contract		1
Trouble debt restructured loan		$ 7,000