Contingent Liabilities - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2012 Accountsholder Age
Commitments And Contingent Liabilities [Line Items]
Minimum interest rate	8.00%
Number of account holders of specified average age	237
Market Rate Savings	$ 11.5
Specified average age of account holders	64
Breach of contract [Member]
Commitments And Contingent Liabilities [Line Items]
Minimum interest rate	3.50%

Amount of interest-bearing domestic savings deposit liabilities. Saving deposits bear interest and have no stated maturity.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.12)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 12

-Article 9

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