Landfill and Environmental Remediation Liabilities - Changes (Detail) - USD ($) $ in Millions	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017
Landfill and environmental remediation liabilities
Interest accretion	$ 47	$ 45
Ending balance, environmental remediation	249
Landfill [Member]
Landfill and environmental remediation liabilities
Beginning balance, landfill	1,675
Obligations incurred and capitalized	41
Obligations settled	(45)
Interest accretion	47
Revisions in estimates and interest rate assumptions	(7)
Acquisitions, divestitures and other adjustments	8
Ending balance, landfill	1,719
Environmental Remediation Liabilities [Member]
Landfill and environmental remediation liabilities
Beginning balance, environmental remediation	251
Obligations settled	(10)
Interest accretion	2
Revisions in estimates and interest rate assumptions	6
Ending balance, environmental remediation	249
San Jacinto Waste Pits [Member]
Landfill and environmental remediation liabilities
Beginning balance, environmental remediation	55
Ending balance, environmental remediation	$ 55

Total costs accrued as of the balance sheet date for environmental loss contingencies.

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