Loans Loans (Summary of Change in Accretable Yield PCI Loans) (Details) - Purchased Impaired Loans [Member] - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Summary of Change in Accretable Yield PCI Loans [Line Items]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield	$ 664	$ 803	$ 664	$ 803	$ 676	$ 745	$ 851	$ 290
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield, Accretion	(12)	(49)	(81)	(135)
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield, Reclassifications from Nonaccretable Difference	0	0	0	0
Certain Loans Acquired in Transfer Not Accounting for as Debt Securities Accretable Yield Other Changes, Net	0	1	0	(13)
First Century Bankshares, Inc [Member]
Summary of Change in Accretable Yield PCI Loans [Line Items]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield, Additions	$ 0	$ 0	$ 0	$ 661

Certain Loans Acquired in Transfer Not Accounting for as Debt Securities Accretable Yield Other Changes, Net

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- Definition

[Line Items] for Summary of Change in Accretable Yield PCI Loans

+ References

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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://fasb.org/us-gaap/role/ref/legacyRef
-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://fasb.org/us-gaap/role/ref/legacyRef
-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

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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

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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

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Amount of increase of reclassification from nonaccretable difference 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.

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