Fair Value - Additional Information (Detail) (USD $)	Jun. 30, 2013	Dec. 31, 2012
Fair Value of Financial Instruments [Line Items]
Impaired loans	$ 38,809,000	$ 48,773,000
Impaired loans fair value	34,500,000	43,600,000
Specific loan loss reserves	$ 4,300,000	$ 5,200,000

Amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 14A

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=28368275&loc=SL6953550-111524

Name:	us-gaap_ImpairedFinancingReceivableRecordedInvestment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant