Prepaid Expenses and Other Assets (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Equipment	$ 300	$ 0
Insurance	18	12
Advertising reimbursements	11	27
Income taxes	4	51
Other	42	50
Prepaid expenses and other assets	$ 375	$ 140