Derivative Instruments - Impact on Statements of Income, Risk Management Derivatives (Details) (Risk Management Activities, Not designated as hedges, USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Gain (Loss) on Derivative Instruments, Net, Pretax [Abstract]
Total income statement impact	$ 621	$ 684
Interest rate contracts
Gain (Loss) on Derivative Instruments, Net, Pretax [Abstract]
Total income statement impact	683	518
Credit derivatives
Gain (Loss) on Derivative Instruments, Net, Pretax [Abstract]
Total income statement impact	(14)	(17)
Foreign exchange contracts
Gain (Loss) on Derivative Instruments, Net, Pretax [Abstract]
Total income statement impact	(12)	0
Commodity contracts
Gain (Loss) on Derivative Instruments, Net, Pretax [Abstract]
Total income statement impact	$ (36)	$ 183