Supplementary Information for Certain Balance Sheet Accounts - Deferred Revenue and Accrued Expenses (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Accounts payable, accrued liabilities and deferred income	$ 832	$ 856
Accrued discretionary and incentive compensation	419	727
Accrued vacation	196	137
Other employee-related liabilities	57	64
Total deferred revenue and accrued expenses	$ 1,504	$ 1,784