Revenue Recognition Revenue Recognition - Retail Value of Complimentaries (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Promotional Allowances	$ 276	$ 283	$ 548	$ 563
Food and Beverage [Member]
Promotional Allowances	143	144	292	295
Rooms [Member]
Promotional Allowances	118	122	226	237
Other [Member]
Promotional Allowances	$ 15	$ 17	$ 30	$ 31