Derivative Instruments - Notional Amount of Derivative Contracts (Details) - USD ($) $ in Billions	Mar. 31, 2019	Dec. 31, 2018
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	$ 59,438	$ 48,239
Interest rate contracts
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	43,380	33,644
Swaps
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	26,342	21,763
Futures and forwards
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	7,369	3,562
Options | Written options
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	4,613	3,997
Options | Purchased options
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	5,056	4,322
Credit derivatives
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	1,366	1,501
Foreign exchange contracts
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	12,530	11,084
Cross-currency swaps
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	3,731	3,548
Spot, futures and forwards
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	6,936	5,871
Options | Written options
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	925	835
Options | Purchased options
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	938	830
Equity contracts
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	1,613	1,465
Swaps
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	373	346
Futures and forwards
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	122	101
Options | Written options
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	586	528
Options | Purchased options
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	532	490
Commodity contracts
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	549	545
Swaps
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	147	134
Spot, futures and forwards
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	152	156
Options | Written options
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	131	135
Options | Purchased options
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	$ 119	$ 120