Revenue - Contract and Contract Related Liabilities (Details) - USD ($) $ in Millions		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Outstanding Chip Liability [Member]
Contract and Contract Related Liabilities [Line Items]
Contract and contract related, liability		$ 676	$ 553	$ 478	$ 525
Change in contract and contract related liabilities		198	28
Loyalty Program Liability [Member]
Contract and Contract Related Liabilities [Line Items]
Contract and contract related, liability		65	63	63	69
Change in contract and contract related liabilities		2	(6)
Customer Deposits and Other Deferred Revenue [Member]
Contract and Contract Related Liabilities [Line Items]
Contract and contract related, liability	[1]	724	642	714	633
Change in contract and contract related liabilities		10	9
Mall Deposits [Member]
Contract and Contract Related Liabilities [Line Items]
Contract and contract related, liability	[1]	$ 150	$ 137	$ 145	$ 131

[1] Of this amount, $150 million, $145 million, $137 million and $131 million as of June 30, 2018, January 1, 2018, June 30, 2017, and January 1, 2017, respectively, relates to mall deposits that are accounted for based on lease terms usually greater than one year.