Goodwill and Intangible Assets - Schedule of Acquired Intangible Assets (Detail) (Core Deposit and Other Intangibles [Member], USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Core Deposit and Other Intangibles [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 6,688	$ 11,619
Accumulated Amortization	$ 5,165	$ 9,326

Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 30

-Section 50

-Paragraph 2

-Subparagraph (a)(1)

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

Name:	us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant