Derivative Instruments - Notional Amount of Derivative Contracts (Details) - USD ($) $ in Billions	Dec. 31, 2018	Dec. 31, 2017
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	$ 48,239	$ 48,403
Interest rate contracts
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	33,644	33,510
Swaps
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	21,763	21,043
Futures and forwards
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	3,562	4,904
Options | Written options
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	3,997	3,576
Options | Purchased options
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	4,322	3,987
Net credit derivatives
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	1,501	1,522
Foreign exchange contracts
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	11,084	11,438
Cross-currency swaps
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	3,548	3,953
Spot, futures and forwards
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	5,871	5,923
Options | Written options
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	835	786
Options | Purchased options
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	830	776
Equity contracts
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	1,465	1,441
Swaps
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	346	367
Futures and forwards
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	101	90
Options | Written options
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	528	531
Options | Purchased options
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	490	453
Commodity contracts
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	545	492
Swaps
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	134	133
Spot, futures and forwards
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	156	168
Options | Written options
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	135	98
Options | Purchased options
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	$ 120	$ 93