Summary of Balance Sheet Classification of Derivative Fair Value Amounts, as well as Gross Asset and Liability Fair Value Amounts (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Derivatives, Fair Value [Line Items]
Net Derivatives Notional Amount	$ 5,491	$ 6,174
Net Derivatives Fair Value	(156)	(177)
Asset Derivatives Fair Value	375	564
Liability Derivatives Fair Value	(531)	(741)
Other assets
Derivatives, Fair Value [Line Items]
Net Derivatives Notional Amount	1,794	2,364
Net Derivatives Fair Value	375	564
Asset Derivatives Fair Value	375	564
Liability Derivatives Fair Value	0	0
Other Liabilities
Derivatives, Fair Value [Line Items]
Net Derivatives Notional Amount	3,697	3,810
Net Derivatives Fair Value	(531)	(741)
Asset Derivatives Fair Value	0	0
Liability Derivatives Fair Value	(531)	(741)
Cash flow hedges
Derivatives, Fair Value [Line Items]
Net Derivatives Notional Amount	146	860
Net Derivatives Fair Value	36	168
Asset Derivatives Fair Value	36	180
Liability Derivatives Fair Value	0	(12)
Cash flow hedges | Interest rate swaps
Derivatives, Fair Value [Line Items]
Net Derivatives Notional Amount	71	245
Net Derivatives Fair Value	0	(2)
Asset Derivatives Fair Value	0	0
Liability Derivatives Fair Value	0	(2)
Cash flow hedges | Foreign currency swaps
Derivatives, Fair Value [Line Items]
Net Derivatives Notional Amount	75	615
Net Derivatives Fair Value	36	170
Asset Derivatives Fair Value	36	180
Liability Derivatives Fair Value	0	(10)
Non-qualifying strategies
Derivatives, Fair Value [Line Items]
Net Derivatives Notional Amount	5,345	5,314
Net Derivatives Fair Value	(192)	(345)
Asset Derivatives Fair Value	339	384
Liability Derivatives Fair Value	(531)	(729)
Non-qualifying strategies | Interest rate swaps
Derivatives, Fair Value [Line Items]
Net Derivatives Notional Amount	381	743
Net Derivatives Fair Value	30	56
Asset Derivatives Fair Value	34	124
Liability Derivatives Fair Value	(4)	(68)
Non-qualifying strategies | Foreign currency swaps
Derivatives, Fair Value [Line Items]
Net Derivatives Notional Amount	4,583	3,815
Net Derivatives Fair Value	(92)	(58)
Asset Derivatives Fair Value	305	260
Liability Derivatives Fair Value	(397)	(318)
Non-qualifying strategies | Credit default swaps
Derivatives, Fair Value [Line Items]
Net Derivatives Notional Amount	381	756
Net Derivatives Fair Value	(130)	(343)
Asset Derivatives Fair Value	0	0
Liability Derivatives Fair Value	(130)	(343)
Cash flow hedges and non-qualifying strategies
Derivatives, Fair Value [Line Items]
Net Derivatives Notional Amount	5,491	6,174
Net Derivatives Fair Value	(156)	(177)
Asset Derivatives Fair Value	375	564
Liability Derivatives Fair Value	$ (531)	$ (741)