Goodwill and Intangible Assets, Net - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Goodwill impairment charges	$ 0	$ 0
Future Amortization Expenses
Future amortization expense, 2020	14
Future amortization expense, 2021	5
Future amortization expense, 2022	3
Future amortization expense, 2023	3
Future amortization expense, 2024	3
Health Plans
Finite-Lived Intangible Assets [Line Items]
Gross goodwill	445	445
Accumulated impairment loss	302	302
Goodwill impairment charges	0	0	$ 244
Future Amortization Expenses
Impairment of intangible assets			25
Other
Finite-Lived Intangible Assets [Line Items]
Goodwill impairment charges	$ 0	$ 0	190
Future Amortization Expenses
Impairment of intangible assets			$ 11