Lines of Businesses- Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013 Segment	Dec. 31, 2012	Mar. 31, 2012
Segment Reporting Information [Line Items]
Provision	$ (24)	$ (61)	$ 5
Number of principal businesses	2
Other
Segment Reporting Information [Line Items]
Provision	(24)	(61)	(11)
Investment Management
Segment Reporting Information [Line Items]
Provision	0	0	0
Investment Services
Segment Reporting Information [Line Items]
Provision	$ 0	$ 0	$ 16