Debt - Outstanding Debt, Debt Issuance Costs, Premium (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Long-term debt	$ 7,609	$ 7,365
Debt issuance costs	33
Debt discount	$ 8
Average remaining term (in years)	5 years 3 months 18 days
Interest accrued for debt	$ 57	$ 52
Secured Debt
Debt Instrument [Line Items]
Average remaining term (in years)	5 years 3 months 18 days