Revenues and Long-Lived Assets by Geographical Area (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Segment Reporting Information [Line Items]
Revenues	$ 1,299	$ 1,254	$ 4,163	$ 4,043
Property and equipment, net	9,775		9,775		$ 9,692
United States
Segment Reporting Information [Line Items]
Revenues	1,271	1,225	4,078	3,947
Property and equipment, net	9,664		9,664		9,548
Australia
Segment Reporting Information [Line Items]
Revenues		2		18
Brazil
Segment Reporting Information [Line Items]
Revenues	4	5	14	16
Property and equipment, net	47		47		59
Canada
Segment Reporting Information [Line Items]
Revenues	17	16	50	42
Property and equipment, net	64		64		71
Mexico
Segment Reporting Information [Line Items]
Revenues	$ 7	$ 6	$ 21	$ 20
Property and equipment, net					$ 14