Landfill and Environmental Remediation Liabilities - Summary (Detail) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Landfill and environmental remediation liabilities
Total, Environmental Remediation	$ 251
Current (in accrued liabilities)	157	$ 156
Long-term	1,795	1,770
Total	1,952	1,926
Landfill [Member]
Landfill and environmental remediation liabilities
Current (in accrued liabilities), Landfill	129	128
Long-term, Landfill	1,572	1,547
Total, Landfill	1,701	1,675
Environmental Remediation Liabilities [Member]
Landfill and environmental remediation liabilities
Current (in accrued liabilities), Environmental Remediation	28	28
Long-term, Environmental Remediation	223	223
Total, Environmental Remediation	$ 251	$ 251