Segment, Geographic and Revenue Information - Trading Revenues by Product Type (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue
Trading revenues	$ 2,608	$ 2,752	$ 8,781	$ 9,815
Interest rate
Disaggregation of Revenue
Trading revenues	894	744	2,283	2,396
Foreign exchange
Disaggregation of Revenue
Trading revenues	69	223	383	622
Equity security and index
Disaggregation of Revenue
Trading revenues	1,076	1,432	4,005	5,094
Commodity and other
Disaggregation of Revenue
Trading revenues	300	254	986	1,047
Credit
Disaggregation of Revenue
Trading revenues	$ 269	$ 99	$ 1,124	$ 656