Revenue - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Revenue, Contract Assets, Liabilities and Costs[Line Items]
Contract liabilities	$ 133		$ 137
Contract liability amortization period	30 months
Deferred incremental direct costs, amortization period	4 years
Deferred incremental direct costs net of accumulated amortization	$ 154		163
Contract Fulfillment Costs and Inducements
Revenue, Contract Assets, Liabilities and Costs[Line Items]
Capitalized contract costs, amounts deferred	13		$ 13
Capitalized contract costs, amortization	$ 1	$ 1