Nature of Operations and Basis of Presentation - Narrative (Details) $ in Millions	6 Months Ended
	Jun. 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	16	7
Unearned revenue	1,500
Revenue expected to be recognized as of period end	2,500
Capitalized contract costs	$ 128	$ 129
Amortization period of capitalized contract cost	5 years