Revenue - Contract Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Contract liabilities
Contract liabilities	$ 206	$ 168
Deferred Revenue Related To Prepaid Stored Value Products [Member]
Contract liabilities
Contract liabilities	117	86
Deferred Revenue Related To Upfront Franchise Fees [Member]
Contract liabilities
Contract liabilities	38	39
Deferred Revenue Related To Customer Loyalty Programs [Member]
Contract liabilities
Contract liabilities	23	24
Deferred Revenue Related To Privilege Membership Programs [Member]
Contract liabilities
Contract liabilities	27	16
Others [Member]
Contract liabilities
Contract liabilities	$ 1	$ 3