Revenue Recognition - Revenue Not Subject to Topic 606 (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenue from Contract with Customer [Abstract]
Total revenue	$ 1,971	$ 1,952	$ 5,935	$ 5,828
Adjustments for non-ASC 606 revenue	(234)	(94)	(687)	(288)
Total revenue from contracts with customers	$ 1,737	$ 1,858	$ 5,248	$ 5,540