Revenue Recognition - Contract With Customer, Assets and Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Contract assets, current	$ 481	$ 529
Total contract assets	481	529
Contract liabilities, current	2,503	2,270
Contract liabilities, noncurrent (included within Other long-term liabilities)	33	18
Total contract liabilities	2,536	2,288
Net contract liabilities	$ 2,055	$ 1,759