Derivative Instruments - Impact on Statements of Income, Risk Management Derivatives (Details 2d) (Risk Management Activities [Member], Not Designated as Hedging Instrument, USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Risk management derivatives gains and losses [Abstract]
Income statement impact	$ 301	$ 2,349	$ 763	$ 2,806
Interest rate contract
Risk management derivatives gains and losses [Abstract]
Income statement impact	269	2,307	727	2,843
Credit derivatives
Risk management derivatives gains and losses [Abstract]
Income statement impact	(8)	(13)	(39)	(87)
Foreign exchange
Risk management derivatives gains and losses [Abstract]
Income statement impact	0	42	1	47
Commodity
Risk management derivatives gains and losses [Abstract]
Income statement impact	$ 40	$ 13	$ 74	$ 3