Derivative instruments - Revenue from Foreign Exchange and Other Trading (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2020	Jun. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Foreign exchange	$ 151	$ 174	$ 129	$ 578	$ 439
Other trading (loss) revenue	(14)	(8)	21	44	47
Total foreign exchange and other trading revenue	$ 137	$ 166	$ 150	$ 622	$ 486

Amount of gain (loss) resulting from the difference between the acquisition price and the selling price or fair value of trading assets and trading liabilities, conducted separately from customer trading activities. Includes, but is not limited to, changes in fair value of trading assets and trading liabilities.

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