Derivative Instruments - Impact on Statements of Income, Risk Management Derivatives (Details) - Risk Management Activities - Not designated as hedges - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Gain (Loss) on Derivative Instruments, Net, Pretax [Abstract]
Total income statement impact	$ (543)	$ 541	$ 78	$ 1,225
Interest rate contracts
Gain (Loss) on Derivative Instruments, Net, Pretax [Abstract]
Total income statement impact	(563)	589	120	1,107
Credit derivatives
Gain (Loss) on Derivative Instruments, Net, Pretax [Abstract]
Total income statement impact	(10)	(24)	(24)	(41)
Foreign exchange contracts
Gain (Loss) on Derivative Instruments, Net, Pretax [Abstract]
Total income statement impact	7	(3)	(5)	(3)
Commodity contracts
Gain (Loss) on Derivative Instruments, Net, Pretax [Abstract]
Total income statement impact	$ 23	$ (21)	$ (13)	$ 162