Derivative Instruments - Notional Amount of Derivative Contracts (Details) - USD ($) $ in Billions	Sep. 30, 2019	Dec. 31, 2018
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	$ 55,548	$ 48,239
Interest rate contracts
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	38,973	33,644
Swaps
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	25,099	21,763
Futures and forwards
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	4,887	3,562
Options | Written options
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	4,290	3,997
Options | Purchased options
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	4,697	4,322
Credit derivatives
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	1,365	1,501
Foreign exchange contracts
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	12,681	11,084
Cross-currency swaps
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	3,886	3,548
Spot, futures and forwards
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	7,111	5,871
Options | Written options
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	832	835
Options | Purchased options
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	852	830
Equity contracts
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	1,844	1,465
Swaps
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	389	346
Futures and forwards
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	131	101
Options | Written options
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	692	528
Options | Purchased options
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	632	490
Commodity contracts
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	685	545
Swaps
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	148	134
Spot, futures and forwards
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	218	156
Options | Written options
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	166	135
Options | Purchased options
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	$ 153	$ 120