Derivative Instruments - Impact on Statements of Income, Risk Management Derivatives (Details) (Risk Management Activities, Not designated as hedges, USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Gain (Loss) on Derivative Instruments, Net, Pretax [Abstract]
Total income statement impact	$ 2,399	$ 654	$ 5,319
Interest rate contracts
Gain (Loss) on Derivative Instruments, Net, Pretax [Abstract]
Total income statement impact	2,308	617	5,353
Credit derivatives
Gain (Loss) on Derivative Instruments, Net, Pretax [Abstract]
Total income statement impact	(58)	(142)	(175)
Foreign exchange contracts
Gain (Loss) on Derivative Instruments, Net, Pretax [Abstract]
Total income statement impact	(7)	1	47
Commodity contracts
Gain (Loss) on Derivative Instruments, Net, Pretax [Abstract]
Total income statement impact	$ 156	$ 178	$ 94