Derivative Instruments (Details 1) (Asset and Liability Management Positions [Member], USD $) In Millions, unless otherwise specified	Mar. 31, 2012 Y	Dec. 31, 2011 Y
Fair Value Hedges [Member] | Foreign exchange cross-currency swaps [Member]
Asset and liability management derivative positions of the company
Notional Value, Assets		$ 688
Notional Value, Liabilities		432
Fair Value, Assets		17
Fair Value, Liabilities		23
Derivative Asset Average Remaining Maturity Period		5.17
Derivative Liability Average Remaining Maturity Period		5.17
Fair Value Hedges [Member] | Interest Rate Contracts [Member] | Receive fixed/pay floating swaps [Member]
Asset and liability management derivative positions of the company
Notional Value, Assets	500	500
Notional Value, Liabilities
Fair Value, Assets	25	27
Fair Value, Liabilities
Derivative Asset Average Remaining Maturity Period	3.84	4.09
Derivative Liability Average Remaining Maturity Period
Cash flow hedges [Member] | Interest Rate Contracts [Member] | Pay fixed/receive floating swaps [Member]
Asset and liability management derivative positions of the company
Notional Value, Assets
Notional Value, Liabilities	4,788	4,788
Fair Value, Assets
Fair Value, Liabilities	765	803
Derivative Asset Average Remaining Maturity Period
Derivative Liability Average Remaining Maturity Period	3.78	4.03
Cash flow hedges [Member] | Interest Rate Contracts [Member] | Receive fixed/pay floating swaps [Member]
Asset and liability management derivative positions of the company
Notional Value, Assets	6,750	750
Notional Value, Liabilities	250	6,250
Fair Value, Assets	12
Fair Value, Liabilities		6
Derivative Asset Average Remaining Maturity Period	2.60	2.75
Derivative Liability Average Remaining Maturity Period	2.42	2.86
Net investment hedges [Member] | Foreign exchange forward contracts [Member]
Asset and liability management derivative positions of the company
Notional Value, Assets		708
Notional Value, Liabilities
Fair Value, Assets		4
Fair Value, Liabilities
Derivative Asset Average Remaining Maturity Period		0.08
Derivative Liability Average Remaining Maturity Period
Other Economic Hedges [Member] | Credit Risk Contract [Member]
Asset and liability management derivative positions of the company
Notional Value, Assets	728	800
Notional Value, Liabilities	1,763	1,600
Fair Value, Assets	2	7
Fair Value, Liabilities	9	8
Derivative Asset Average Remaining Maturity Period	3.93	3.71
Derivative Liability Average Remaining Maturity Period	3.44	3.59
Other Economic Hedges [Member] | Equity Contract [Member]
Asset and liability management derivative positions of the company
Notional Value, Assets	72	54
Notional Value, Liabilities		10
Fair Value, Assets	4	1
Fair Value, Liabilities
Derivative Asset Average Remaining Maturity Period	0.74	1.05
Derivative Liability Average Remaining Maturity Period		0.64
Other Economic Hedges [Member] | Interest Rate Contracts [Member] | Receive fixed/pay floating swaps [Member]
Asset and liability management derivative positions of the company
Notional Value, Assets	400	2,625
Notional Value, Liabilities	3,125
Fair Value, Assets		9
Fair Value, Liabilities	14
Derivative Asset Average Remaining Maturity Period	10.21	10.21
Derivative Liability Average Remaining Maturity Period	10.21
Other Economic Hedges [Member] | Interest Rate Contracts [Member] | Futures and Forwards Buy [Member]
Asset and liability management derivative positions of the company
Notional Value, Assets	12,502	14,270
Notional Value, Liabilities	2,332	29
Fair Value, Assets	92	150
Fair Value, Liabilities	13
Derivative Asset Average Remaining Maturity Period	0.10	0.07
Derivative Liability Average Remaining Maturity Period	0.04	0.12
Other Economic Hedges [Member] | Interest Rate Contracts [Member] | Futures and Forwards Sell [Member]
Asset and liability management derivative positions of the company
Notional Value, Assets	8,626	231
Notional Value, Liabilities	7,359	14,415
Fair Value, Assets	32	1
Fair Value, Liabilities	29	134
Derivative Asset Average Remaining Maturity Period	0.10	0.15
Derivative Liability Average Remaining Maturity Period	0.13	0.11
Other Economic Hedges [Member] | Interest Rate Contracts [Member] | Purchased Option [Member]
Asset and liability management derivative positions of the company
Notional Value, Assets	3,810	1,250
Notional Value, Liabilities
Fair Value, Assets
Fair Value, Liabilities
Derivative Asset Average Remaining Maturity Period	0.05	0.07
Derivative Liability Average Remaining Maturity Period
Other Economic Hedges [Member] | Interest Rate Contracts [Member] | Written Option [Member]
Asset and liability management derivative positions of the company
Notional Value, Assets	6,223	4,421
Notional Value, Liabilities	17	11
Fair Value, Assets	86	80
Fair Value, Liabilities	0	1
Derivative Asset Average Remaining Maturity Period	0.11	0.10
Derivative Liability Average Remaining Maturity Period	0.14	0.13
Other Economic Hedges [Member] | Foreign exchange forward contracts [Member]
Asset and liability management derivative positions of the company
Notional Value, Assets	1,018	261
Notional Value, Liabilities	312	567
Fair Value, Assets	3	1
Fair Value, Liabilities	$ 2	$ 5
Derivative Asset Average Remaining Maturity Period	0.08	0.08
Derivative Liability Average Remaining Maturity Period	0.09	0.09