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Acquisition - Additional Information (Detail)		12 Months Ended
	Apr. 17, 2015 USD ($) Branches	Dec. 31, 2015 Branch
Business Acquisition [Line Items]
Cash paid for deposits, premises and equipment	$ 6,618,000
Amount for acquisition of premises and equipment	4,495,000
Total deposits liabilities assumed	186,819,000
Bank of America [Member]
Business Acquisition [Line Items]
Number of acquired branches | Branch		6
Amount for acquisition of premises and equipment	2,165,000
Total deposits liabilities assumed	186,136,000
Loans acquired	$ 0
Bank of America [Member] | Virginia [Member]
Business Acquisition [Line Items]
Number of acquired branches | Branches	6

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Business combination recognized identifiable assets acquired and liabilities assumed loans.

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- Definition

Amount of liabilities assumed at the acquisition date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=56956791&loc=d3e4845-128472

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- Definition

The amount of property, plant, and equipment recognized as of the acquisition date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=56956791&loc=d3e4845-128472

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 55
-Paragraph 37
-URI http://asc.fasb.org/extlink&oid=35744172&loc=d3e2207-128464

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- Definition

The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Investing Activities
-URI http://asc.fasb.org/extlink&oid=6516133

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
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-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3213-108585

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