Revenue from Contracts with Customers - Remaining Transaction Price (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($)
Advanced deposits
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Remaining Transaction Price	$ 101
Recognition Period	18 months
Recognition Method	0
Club Activation Fees
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Remaining Transaction Price	$ 63
Recognition Period	7 years
Recognition Method	0
Club Bonus Points
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Remaining Transaction Price	$ 56
Recognition Period	24 months
Recognition Method	0