Rental expense incurred for leased assets including furniture and equipment which has not been recognized in costs and expenses applicable to sales and revenues; for example, cost of goods sold or other operating costs and expenses.

No definition available.

Name:	us-gaap_LeaseAndRentalExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Commitments and Contingencies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Aug. 28, 2008 Total Bond Market Fund Litigation	Dec. 31, 2012 Margin Requirements	Dec. 31, 2012 Collateral Requirements
Commitments and Contingencies Disclosure [Line Items]
Rent expense	$ 203	$ 187	$ 168
Aggregate face amount of letter of credit agreements					$ 325	$ 74
Alleged minimum percentage of fund assets invested in CMOs and mortgage-backed securities without obtaining shareholder vote				25.00%