Derivative Instruments - Notional Amount of Derivative Contracts (Details) - USD ($) $ in Billions	Jun. 30, 2019	Dec. 31, 2018
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	$ 56,017	$ 48,239
Interest rate contracts
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	39,809	33,644
Swaps
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	25,583	21,763
Futures and forwards
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	4,600	3,562
Options | Written options
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	4,572	3,997
Options | Purchased options
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	5,054	4,322
Credit derivatives
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	1,294	1,501
Foreign exchange contracts
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	12,636	11,084
Cross-currency swaps
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	3,824	3,548
Spot, futures and forwards
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	6,951	5,871
Options | Written options
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	922	835
Options | Purchased options
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	939	830
Equity contracts
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	1,700	1,465
Swaps
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	365	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	640	528
Options | Purchased options
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	573	490
Commodity contracts
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	578	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	161	156
Options | Written options
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	143	135
Options | Purchased options
Notional amount of derivative contracts outstanding [Abstract]
Derivative notional amounts	$ 126	$ 120