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	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Risk management derivatives gains and losses [Abstract]
Income statement impact	$ 5,319	$ 7,916	$ 4,638
Interest Rate Contract [Member]
Risk management derivatives gains and losses [Abstract]
Income statement impact	5,353	8,084	4,987
Credit derivatives
Risk management derivatives gains and losses [Abstract]
Income statement impact	(175)	(52)	(237)
Foreign exchange
Risk management derivatives gains and losses [Abstract]
Income statement impact	47	(157)	(64)
Commodity
Risk management derivatives gains and losses [Abstract]
Income statement impact	$ 94	$ 41	$ (48)