Derivatives - Additional Information (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Securities pledged for collateral	$ 1,500,000	$ 497,000

The fair value of trading securities that serve as collateral for borrowings.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=28368275&loc=d3e5086-111524

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