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Loans and Allowance for Loan Losses - Purchased Credit-Impaired (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
PCI Loans, Carrying Value [Abstract]
Unpaid Principal Balance	$ 2,707		$ 2,868
Carrying Value	2,135		2,115
Accretable Yield [Roll Forward]
Balance at beginning of period	1,254	$ 1,476
Accretion	(112)	(90)
Balance at end of period	1,142	$ 1,386
Commercial loans | Commercial and industrial
PCI Loans, Carrying Value [Abstract]
Unpaid Principal Balance	141		276
Carrying Value	52		65
Commercial real estate loans | Commercial real estate, owner-occupied
PCI Loans, Carrying Value [Abstract]
Unpaid Principal Balance	1,284		1,297
Carrying Value	1,194		1,166
Commercial real estate loans | Commercial real estate, investor
PCI Loans, Carrying Value [Abstract]
Unpaid Principal Balance	1,056		1,064
Carrying Value	797		790
Residential loans | Home equity
PCI Loans, Carrying Value [Abstract]
Unpaid Principal Balance	226		231
Carrying Value	$ 92		$ 94

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- References

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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
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=82894903&loc=d3e15032-111544

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 15
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-URI http://asc.fasb.org/extlink&oid=82894507&loc=d3e13503-111538

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- Definition

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 15
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82894507&loc=d3e13503-111538

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=82894903&loc=d3e15032-111544

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-Publisher FASB
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-URI http://asc.fasb.org/extlink&oid=82894507&loc=d3e13503-111538

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Topic 310
-SubTopic 30
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-URI http://asc.fasb.org/extlink&oid=82894507&loc=d3e13503-111538

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