Other Financial Information (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Prepaid Expenses and Other Current Assets [Abstract]
Prepaid expenses	$ 340	$ 274
Income tax receivable	69	35
Materials, supplies and inventory	122	105
Contract assets	33	42
Other	63	70
Total other current assets	913	819
Acquisition Costs
Prepaid Expenses and Other Current Assets [Abstract]
Contract costs	175	178
Fulfillment Costs
Prepaid Expenses and Other Current Assets [Abstract]
Contract costs	$ 111	$ 115