Derivative Instruments - Impact on Statements of Income, Risk Management Derivatives (Details 2d) (Risk Management Activities [Member], Not Designated as Hedging Instrument [Member], USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Risk management derivatives gains and losses [Abstract]
Income statement impact	$ 457	$ 9
Interest rate contract
Risk management derivatives gains and losses [Abstract]
Income statement impact	536	75
Credit derivatives
Risk management derivatives gains and losses [Abstract]
Income statement impact	(74)	(58)
Foreign exchange
Risk management derivatives gains and losses [Abstract]
Income statement impact	5	(8)
Commodity Contract
Risk management derivatives gains and losses [Abstract]
Income statement impact	$ (10)	$ 0