Commitments and Contingencies - Future Minimum Payments Under Non-Cancelable Operating Leases (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012
Operating Leased Assets [Line Items]
2013	$ 157
2014	109
2015	74
2016	50
2017	44
Thereafter	85
Total minimum payments required	519
Less: Sublease rentals under non-cancelable leases	6
Net minimum payments required	513
Real estate securities [Member]
Operating Leased Assets [Line Items]
2013	149
2014	104
2015	72
2016	49
2017	43
Thereafter	84
Total minimum payments required	501
Less: Sublease rentals under non-cancelable leases	6
Net minimum payments required	495
Equipment [Member]
Operating Leased Assets [Line Items]
2013	8
2014	5
2015	2
2016	1
2017	1
Thereafter	1
Total minimum payments required	18
Less: Sublease rentals under non-cancelable leases
Net minimum payments required	$ 18