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Loans and Allowance for Loan Losses - Troubled Debt Restructuring Modifications (Details)	12 Months Ended
	Dec. 31, 2017 USD ($) contract	Dec. 31, 2016 USD ($) contract	Dec. 31, 2015 USD ($) contract
Financing Receivable, Modifications [Line Items]
Number of Contracts Modified | contract		4
Pre-Modification Outstanding Recorded Investment		$ 1,985,000
Post-Modification Outstanding Recorded Investment		2,115,000
Post-Modification Outstanding Recorded Investment at Period End		2,063,000
Total of TDR loans charged-off within previous 12 months	$ 0	$ 0	$ 0
Consumer loans | Installment and other consumer
Financing Receivable, Modifications [Line Items]
Number of Contracts Modified | contract	1	1
Pre-Modification Outstanding Recorded Investment	$ 50,000	$ 68,000
Post-Modification Outstanding Recorded Investment	50,000	67,000
Post-Modification Outstanding Recorded Investment at Period End	$ 47,000	$ 66,000
Commercial | Commercial real estate, investor
Financing Receivable, Modifications [Line Items]
Number of Contracts Modified | contract		2
Pre-Modification Outstanding Recorded Investment		$ 1,830,000
Post-Modification Outstanding Recorded Investment		1,826,000
Post-Modification Outstanding Recorded Investment at Period End		$ 1,752,000
Commercial | Commercial and industrial
Financing Receivable, Modifications [Line Items]
Number of Contracts Modified | contract			7
Pre-Modification Outstanding Recorded Investment			$ 3,271,000
Post-Modification Outstanding Recorded Investment			3,251,000
Post-Modification Outstanding Recorded Investment at Period End			$ 2,811,000
Residential loans | Home equity
Financing Receivable, Modifications [Line Items]
Number of Contracts Modified | contract		1
Pre-Modification Outstanding Recorded Investment		$ 87,000
Post-Modification Outstanding Recorded Investment		222,000
Post-Modification Outstanding Recorded Investment at Period End		$ 245,000

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- Definition

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

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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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+ References

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-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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+ 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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-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953682-111524

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