Other Financial Information (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Prepaid Expenses and Other Current Assets [Abstract]
Prepaid expenses	$ 333	$ 274
Income tax receivable	73	35
Materials, supplies and inventory	119	105
Contract assets	33	42
Other	85	59
Total other current assets	941	808
Acquisition Costs
Prepaid Expenses and Other Current Assets [Abstract]
Contract costs	180	178
Fulfillment Costs
Prepaid Expenses and Other Current Assets [Abstract]
Contract costs	$ 118	$ 115