Revenue Recognition - Revenue not Under ASC 606 (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Revenue from Contract with Customer [Abstract]
Total revenue	[1]	$ 1,918	$ 2,030
Adjustments for non-ASC 606 revenue		(121)	(127)
Total revenue from contracts with customers		$ 1,797	$ 1,903

[1] Reclassifications were made within certain 2019 comparative figures due to the retrospective application of an accounting policy election during the first quarter of 2020. Refer to Note 1—Background and our Form 8-K filing dated May 7, 2020 for further information.