Segment, Geographic and Revenue Information - Revenue Recognized from Prior Services (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting [Abstract]
Non-interest revenues	$ 841	$ 804	$ 1,995	$ 2,192