Landfill and Environmental Remediation Liabilities - Summary (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Landfill and environmental remediation liabilities
Current (in accrued liabilities)	$ 156	$ 147
Long-term	1,770	1,675
Total	1,926	1,822
Landfill [Member]
Landfill and environmental remediation liabilities
Current (in accrued liabilities), Landfill	128	119
Long-term, Landfill	1,547	1,457
Total, Landfill	1,675	1,576
Total, Environmental Remediation	251
Environmental Remediation Liabilities [Member]
Landfill and environmental remediation liabilities
Current (in accrued liabilities), Environmental Remediation	28	28
Long-term, Environmental Remediation	223	218
Total, Environmental Remediation	$ 251	$ 246