Landfill and Environmental Remediation Liabilities - Summary (Detail) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Landfill and environmental remediation liabilities
Total, Environmental Remediation	$ 237
Current (in accrued liabilities)	158	$ 156
Long-term	1,832	1,770
Total	1,990	1,926
Landfill [Member]
Landfill and environmental remediation liabilities
Current (in accrued liabilities), Landfill	131	128
Long-term, Landfill	1,622	1,547
Total, Landfill	1,753	1,675
Environmental Remediation Liabilities [Member]
Landfill and environmental remediation liabilities
Current (in accrued liabilities), Environmental Remediation	27	28
Long-term, Environmental Remediation	210	223
Total, Environmental Remediation	$ 237	$ 251