Derivative Instruments and Other Financial Instruments Used For Hedging - Notional and Fair Value Amounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Derivative Instruments and Other Financial Instruments
Derivative Notional Amount	$ 129,600	$ 71,679
Fair Value, Asset Derivatives	1,828	1,799
Fair Value, Liability Derivatives	1,647	1,624
Not designated as hedging instruments | Trading derivatives
Derivative Instruments and Other Financial Instruments
Derivative Notional Amount	113,599	61,143
Fair Value, Asset Derivatives	1,750	1,761
Fair Value, Liability Derivatives	1,631	1,617
Not designated as hedging instruments | Other risk management
Derivative Instruments and Other Financial Instruments
Derivative Notional Amount	251	286
Fair Value, Asset Derivatives	5	2
Fair Value, Liability Derivatives	2	3
Net gain (losses) on derivatives included in other noninterest income	(3)	(1)
Interest rate contracts | Not designated as hedging instruments | Trading derivatives
Derivative Instruments and Other Financial Instruments
Derivative Notional Amount	100,932	46,944
Fair Value, Asset Derivatives	1,002	933
Fair Value, Liability Derivatives	948	830
Interest rate contracts | Cash Flow Hedges | Designated as hedging instrument
Derivative Instruments and Other Financial Instruments
Derivative Notional Amount	15,250	9,750
Fair Value, Asset Derivatives	68	34
Fair Value, Liability Derivatives	14	4
Interest rate contracts | Fair Value Hedges | Designated as hedging instrument
Derivative Instruments and Other Financial Instruments
Derivative Notional Amount	500	500
Fair Value, Asset Derivatives	5	2
Fair Value, Liability Derivatives	0	0
Commodity contracts | Not designated as hedging instruments | Trading derivatives
Derivative Instruments and Other Financial Instruments
Derivative Notional Amount	3,775	4,741
Fair Value, Asset Derivatives	409	422
Fair Value, Liability Derivatives	369	408
Foreign exchange contracts | Not designated as hedging instruments | Trading derivatives
Derivative Instruments and Other Financial Instruments
Derivative Notional Amount	5,541	5,661
Fair Value, Asset Derivatives	117	106
Fair Value, Liability Derivatives	93	80
Equity contracts | Not designated as hedging instruments | Trading derivatives
Derivative Instruments and Other Financial Instruments
Derivative Notional Amount	3,351	3,797
Fair Value, Asset Derivatives	222	300
Fair Value, Liability Derivatives	$ 221	$ 299