Properties and Equipment - Rollforward Asset Retirement Obligation (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning Balance		$ 72	$ 39
Liabilities incurred during the period		11	8
Liabilities settled during the period		(4)	(7)
Estimate revisions		14	30
Accretion expense	[1]	4	2
Ending Balance		97	72
Amount reflected as current		$ 5	$ 5

[1] Accretion expense is included in lease and facility operating expense on the Consolidated Statements of Operations.