Landfill and Environmental Remediation Liabilities - Summary (Detail) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Landfill and environmental remediation liabilities
Total, Environmental Remediation	$ 249
Current (in accrued liabilities)	158	$ 156
Long-term	1,810	1,770
Total	1,968	1,926
Landfill [Member]
Landfill and environmental remediation liabilities
Current (in accrued liabilities), Landfill	130	128
Long-term, Landfill	1,589	1,547
Total, Landfill	1,719	1,675
Environmental Remediation Liabilities [Member]
Landfill and environmental remediation liabilities
Current (in accrued liabilities), Environmental Remediation	28	28
Long-term, Environmental Remediation	221	223
Total, Environmental Remediation	$ 249	$ 251