Revenue - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Revenue, Contract Assets, Liabilities and Costs[Line Items]
Contract liabilities	$ 126		$ 130
Contract liability amortization period (months)	30 months
Deferred incremental direct costs, amortization period (years)	4 years
Deferred incremental direct costs net of accumulated amortization	$ 140		145
Contract Fulfillment Costs and Inducements
Revenue, Contract Assets, Liabilities and Costs[Line Items]
Capitalized contract costs, amounts deferred	17		$ 13
Capitalized contract costs, amortization	$ 1	$ 1