Fair Value Measurement - Quantitative Information about Level 3 Fair Value Measurements (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
Mar. 31, 2015	Dec. 31, 2014
Impaired Loans [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Estimate	10,061	10,126
Impaired Loans [Member] \| Appraisal of Collateral [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Measurements, Valuation Technique	Appraisal of collateral	Appraisal of collateral
Impaired Loans [Member] \| Discounted Cash Flows [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Measurements, Valuation Technique	Discounted cash flows	Discounted cash flows
Other Real Estate Owned [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Estimate	528	560
Other Real Estate Owned [Member] \| Appraisal of Collateral [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Measurements, Valuation Technique	Appraisal of collateral	Appraisal of collateral
Maximum [Member] \| Impaired Loans [Member] \| Appraisal of Collateral [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Assumptions, Appraisal adjustments	30.00%	30.00%
Fair Value Assumptions, Liquidation expense	10.00%	10.00%
Fair Value Assumptions, Holding period	30 months	30 months
Maximum [Member] \| Impaired Loans [Member] \| Discounted Cash Flows [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Assumptions, Discount rates	8.00%	8.00%
Maximum [Member] \| Other Real Estate Owned [Member] \| Appraisal of Collateral [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Assumptions, Appraisal adjustments	30.00%	30.00%
Fair Value Assumptions, Liquidation expense	10.00%	10.00%
Minimum [Member] \| Impaired Loans [Member] \| Appraisal of Collateral [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Assumptions, Appraisal adjustments	10.00%	10.00%
Fair Value Assumptions, Liquidation expense	0.00%	0.00%
Fair Value Assumptions, Holding period	0 months	0 months
Minimum [Member] \| Impaired Loans [Member] \| Discounted Cash Flows [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Assumptions, Discount rates	3.80%	3.80%
Minimum [Member] \| Other Real Estate Owned [Member] \| Appraisal of Collateral [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Assumptions, Appraisal adjustments	10.00%	10.00%
Fair Value Assumptions, Liquidation expense	0.00%	0.00%

Percentage of adjustment to the observed price for a similar asset, used as an input to measure fair value.

No definition available.

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- Definition

Interest rate used to find the present value of an amount to be paid or received in the future as an input to measure fair value. For example, but not limited to, weighted average cost of capital (WACC), cost of capital, cost of equity and cost of debt.

+ References

No definition available.

+ Details

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- Definition

Fair value inputs holding period.

+ References

No definition available.

+ Details

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- Definition

Percentage of adjustment to the observed price to dispose of asset, used as an input to measure fair value.

+ References

No definition available.

+ Details

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- Definition

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258

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- Definition

Description of the inputs and valuation technique(s) used to measure fair value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (bbb)

-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258

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