Netting Arrangements for Certain Financial Instruments - Additional Information (Detail) (USD $) In Billions, unless otherwise specified	Sep. 30, 2013
Derivatives, Fair Value [Line Items]
Notional amount of derivative	$ 105.3
Exchange Cleared [Member]
Derivatives, Fair Value [Line Items]
Notional amount of derivative	6.7
Exchange Traded [Member]
Derivatives, Fair Value [Line Items]
Notional amount of derivative	$ 3.3

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 12

-Section 13

-Sentence Column B

Name:	invest_DerivativeNotionalAmount
Namespace Prefix:	invest_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant