Revenue Recognition - Revenue not Under ASC 606 (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenue from Contract with Customer [Abstract]
Total revenue	$ 5,192	$ 5,375	$ 10,420	$ 10,802
Adjustments for non-ASC 606 revenue	(481)	(356)	(962)	(714)
Total revenue from contracts with customers	$ 4,711	$ 5,019	$ 9,458	$ 10,088