Revenues and Long-Lived Assets by Geographical Area (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Segment Reporting Information [Line Items]
Revenues	$ 1,518	$ 1,441	$ 2,864	$ 2,789
Property and equipment, net	10,377		10,377		$ 9,692
United States
Segment Reporting Information [Line Items]
Revenues	1,487	1,406	2,807	2,722
Property and equipment, net	10,249		10,249		9,548
Australia
Segment Reporting Information [Line Items]
Revenues		8		16
Brazil
Segment Reporting Information [Line Items]
Revenues	5	5	10	11
Property and equipment, net	49		49		59
Canada
Segment Reporting Information [Line Items]
Revenues	19	15	33	26
Property and equipment, net	66		66		71
Mexico
Segment Reporting Information [Line Items]
Revenues	7	$ 7	14	$ 14
Property and equipment, net	$ 13		$ 13		$ 14