Revenue - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Revenue, Contract Assets, Liabilities and Costs[Line Items]
Contract liabilities	$ 127		$ 127		$ 137
Contract liability amortization period			30 months
Deferred incremental direct costs, amortization period	4 years		4 years
Deferred incremental direct costs net of accumulated amortization	$ 148		$ 148		163
Contract Fulfillment Costs and Inducements
Revenue, Contract Assets, Liabilities and Costs[Line Items]
Capitalized contract costs, amounts deferred	12		12		$ 13
Capitalized contract costs, amortization	$ 1	$ 2	$ 2	$ 3