Goodwill and Other Intangible Assets - Additional Information (Detail) (USD $)	12 Months Ended
Dec. 31, 2014 Event	Dec. 31, 2013	Dec. 31, 2012
Goodwill and Intangible Assets Disclosure [Abstract]
Acquisition of core deposits	$ 2,100,000
Acquisition of wealth management relationships	100,000
Acquisition of insurance contract relationships	400,000
Number of triggering events	0
Amortization expense on finite-lived intangible assets	$ 1,129,000us-gaap_AmortizationOfIntangibleAssets	$ 1,591,000us-gaap_AmortizationOfIntangibleAssets	$ 1,709,000us-gaap_AmortizationOfIntangibleAssets

Intangible assets arising from core deposits acquired in business combination.

No definition available.

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- Definition

Intangible assets arising from wealth management acquired in business combination.

+ References

No definition available.

+ Details

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- Definition

Number of triggering events for impairment analysis.

+ References

No definition available.

+ Details

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- Definition

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 30

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6388964&loc=d3e16225-109274

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 30

-Section 50

-Paragraph 2

-Subparagraph (a)(2)

-URI http://asc.fasb.org/extlink&oid=26713463&loc=d3e16323-109275

+ Details

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- Details

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- Definition

Carrying amount as of the balance sheet date of the intangible assets from insurance contracts acquired in a business combination.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 20

-Section S99

-Paragraph 2

-Subparagraph (2)

-URI http://asc.fasb.org/extlink&oid=27015749&loc=d3e569990-122904

+ Details

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