Investment Securities - Additional Information (Detail) $ in Thousands	12 Months Ended
Dec. 31, 2016 USD ($) Bond	Dec. 31, 2015 USD ($) Bond
Schedule of Available-for-sale Securities [Line Items]
Average yields (taxable equivalent) on securities	3.09%	2.55%
Market value of securities	$ 19,100	$ 8,600
Securities sold under repurchase agreements	18,310	7,161
Company's investment in Federal Home Loan Bank stock	1,900	2,000
Company's investment in Federal Reserve Bank stock	$ 580	$ 505
Municipal Securities
Schedule of Available-for-sale Securities [Line Items]
Bonds with unrealized loss positions \| Bond	39	17
US Government Agencies
Schedule of Available-for-sale Securities [Line Items]
Bonds with unrealized loss positions \| Bond	37	5
Corporate Bonds
Schedule of Available-for-sale Securities [Line Items]
Bonds with unrealized loss positions \| Bond	1	1

Available for sale securities average yield.

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- Definition

The fair value of available-for-sale securities that serve as collateral for borrowings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=66008989&loc=d3e5086-111524

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- Definition

Number of investment positions in available-for-sale investments in a continuous unrealized loss position for which an other-than-temporary impairment (OTTI) has not been recognized in the income statement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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- Definition

Federal Home Loan Bank (FHLB) stock represents an equity interest in a FHLB. It does not have a readily determinable fair value because its ownership is restricted and it lacks a market (liquidity).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 325
-Section 45
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-URI http://asc.fasb.org/extlink&oid=6478792&loc=d3e63345-112809

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- Definition

Federal Reserve Bank stock represents an equity interest in the Federal Reserve Bank. It does not have a readily determinable fair value because its ownership is restricted and it lacks a market (liquidity).

+ References

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Amount, after the effects of master netting arrangements, of funds outstanding borrowed in the form of a security repurchase agreement between the entity and another party for the sale and repurchase of identical or substantially the same securities at a date certain for a specified price. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
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-Subparagraph (c)
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Reference 6: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Glossary Repurchase Agreement Accounted for as a Collateralized Borrowing
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