Derivative Instruments - Asset and Liability Management Derivative Positions of Company (Detail) (Asset and Liability Management Positions [Member], USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Derivative [Line Items]
Notional Value, Assets	$ 36,500	$ 35,234
Fair Value, Assets	289	363
Notional Value, Liabilities	19,476	26,808
Fair Value, Liabilities	742	818
Fair value hedges [Member] | Interest rate contracts [Member] | Receive fixed/pay floating swaps [Member]
Derivative [Line Items]
Notional Value, Assets	500	500
Fair Value, Assets	25	30
Derivative Asset Average Remaining Maturity Period	2.84	3.09
Cash flow hedges [Member] | Interest rate contracts [Member] | Receive fixed/pay floating swaps [Member]
Derivative [Line Items]
Notional Value, Assets	7,000	7,000
Fair Value, Assets	39	45
Derivative Asset Average Remaining Maturity Period	1.60	1.84
Cash flow hedges [Member] | Interest rate contracts [Member] | Pay fixed/receive floating swaps [Member]
Derivative [Line Items]
Notional Value, Assets	272	32
Fair Value, Assets	3
Derivative Asset Average Remaining Maturity Period	9.52	9.88
Notional Value, Liabilities	4,288	4,528
Fair Value, Liabilities	664	718
Derivative Liability Average Remaining Maturity Period	3.21	3.79
Net investment hedges [Member] | Foreign exchange forward contracts [Member]
Derivative [Line Items]
Notional Value, Assets	757	758
Fair Value, Assets	5	1
Derivative Asset Average Remaining Maturity Period	0.05	0.07
Other economic hedges [Member] | Interest rate contracts [Member] | Receive fixed/pay floating swaps [Member]
Derivative [Line Items]
Notional Value, Assets	3,945	350
Fair Value, Assets	22	1
Derivative Asset Average Remaining Maturity Period	10.23	10.21
Notional Value, Liabilities		3,775
Fair Value, Liabilities		14
Derivative Liability Average Remaining Maturity Period		10.21
Other economic hedges [Member] | Interest rate contracts [Member] | Futures and forwards buy [Member]
Derivative [Line Items]
Notional Value, Assets	8,397	11,164
Fair Value, Assets	66	138
Derivative Asset Average Remaining Maturity Period	0.08	0.07
Notional Value, Liabilities	172	2,921
Fair Value, Liabilities	1	13
Derivative Liability Average Remaining Maturity Period	0.04	0.04
Other economic hedges [Member] | Interest rate contracts [Member] | Futures and forwards sell [Member]
Derivative [Line Items]
Notional Value, Assets	3,301	6,299
Fair Value, Assets	25	18
Derivative Asset Average Remaining Maturity Period	0.07	0.11
Notional Value, Liabilities	11,098	12,223
Fair Value, Liabilities	52	57
Derivative Liability Average Remaining Maturity Period	0.11	0.09
Other economic hedges [Member] | Interest rate contracts [Member] | Purchased options [Member]
Derivative [Line Items]
Notional Value, Assets	4,325	2,435
Derivative Asset Average Remaining Maturity Period	0.08	0.07
Other economic hedges [Member] | Interest rate contracts [Member] | Written options [Member]
Derivative [Line Items]
Notional Value, Assets	5,506	4,991
Fair Value, Assets	97	123
Derivative Asset Average Remaining Maturity Period	0.10	0.12
Notional Value, Liabilities	10	4
Fair Value, Liabilities	1
Derivative Liability Average Remaining Maturity Period	0.06	0.06
Other economic hedges [Member] | Foreign exchange forward contracts [Member]
Derivative [Line Items]
Notional Value, Assets	1,360	618
Fair Value, Assets	3	4
Derivative Asset Average Remaining Maturity Period	0.01	0.03
Notional Value, Liabilities	1,869	1,383
Fair Value, Liabilities	13	6
Derivative Liability Average Remaining Maturity Period	0.02	0.01
Other economic hedges [Member] | Equity contracts [Member]
Derivative [Line Items]
Notional Value, Assets	41	31
Derivative Asset Average Remaining Maturity Period	2.22	2.80
Notional Value, Liabilities	27	27
Derivative Liability Average Remaining Maturity Period	2.63	2.46
Other economic hedges [Member] | Credit contracts [Member]
Derivative [Line Items]
Notional Value, Assets	1,096	1,056
Fair Value, Assets	4	3
Derivative Asset Average Remaining Maturity Period	4.70	4.56
Notional Value, Liabilities	2,012	1,947
Fair Value, Liabilities	$ 11	$ 10
Derivative Liability Average Remaining Maturity Period	3.02	3.11