Nature of Operations and Basis of Presentation - Narrative (Details) $ in Millions	9 Months Ended
	Sep. 30, 2021 USD ($) segment	Dec. 31, 2020 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of reportable segments | segment	4
Restricted cash	$ 8	$ 14
Contract asset	17	7
Unearned revenue	1,900
Revenue expected to be recognized as of period end	2,500
Capitalized contract costs	$ 127	$ 129
Amortization period of capitalized contract cost	5 years