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Loans and Allowance for Loan Losses - Purchased Credit-Impaired Loans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
PCI Loans, Carrying Value [Abstract]
Unpaid Principal Balance	$ 2,868	$ 3,350
Carrying Value	2,115	2,920
Accretable Yield [Roll Forward]
Balance at beginning of period	1,476	2,618	$ 4,027
Additions	109	0	0
Removals	0	(778)	(914)
Accretion	(331)	(364)	(495)
Balance at end of period	1,254	1,476	$ 2,618
Commercial | Commercial and industrial
PCI Loans, Carrying Value [Abstract]
Unpaid Principal Balance	276	45
Carrying Value	65	40
Commercial real estate | Commercial real estate, owner-occupied
PCI Loans, Carrying Value [Abstract]
Unpaid Principal Balance	1,297	1,344
Carrying Value	1,166	1,072
Commercial real estate | Commercial real estate, investor
PCI Loans, Carrying Value [Abstract]
Unpaid Principal Balance	1,064	1,713
Carrying Value	790	1,706
Commercial real estate | Construction
PCI Loans, Carrying Value [Abstract]
Unpaid Principal Balance	0	0
Carrying Value	0	0
Residential loans | Home equity
PCI Loans, Carrying Value [Abstract]
Unpaid Principal Balance	231	248
Carrying Value	$ 94	$ 102

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- Definition

Amount of the excess of a loan's cash flows expected to be collected over the investor's initial investment in acquired loans not accounted for as debt securities with evidence of deterioration of credit quality.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 50
-Paragraph 2
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Amount of accretion recognized for the excess of a loan's cash flows expected to be collected over the investor's initial investment in acquired loans not accounted for as debt securities, with evidence of deterioration of credit quality.

+ References

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Amount of additions to the excess of a loan's cash flows expected to be collected over the investor's initial investment in acquired loans not accounted for as debt securities with evidence of deterioration of credit quality.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Amount of reduction, resulting from a sale or transfer of a loan, in the excess of a loan's cash flows expected to be collected over the investor's initial investment in acquired loans not accounted for as debt securities with evidence of deterioration of credit quality.

+ References

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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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The recorded balance, net of any applicable reductions (for example, unamortized accretable yield and allowance for loan losses). This relates to loans not accounted for debt securities with evidence of deterioration of credit quality since origination that were acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

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The undiscounted sum of all amounts, including amounts deemed principal, interest, fees, penalties, and other under the loan, owed to the investor at the reporting date, whether or not currently due and whether or not any such amounts have been written or charged off by the investor. This relates to loans not accounted for as debt securities, with evidence of deterioration of credit quality since origination that were acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

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