Landfill and Environmental Remediation Liabilities - Summary (Detail) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Landfill and environmental remediation liabilities
Total, Environmental Remediation	$ 238
Current (in accrued liabilities)	129	$ 165
Long-term	2,037	1,930
Total	2,166	2,095
Landfill [Member]
Landfill and environmental remediation liabilities
Current (in accrued liabilities), Landfill	102	138
Long-term, Landfill	1,826	1,717
Total, Landfill	1,928	1,855
Environmental Remediation Liabilities [Member]
Landfill and environmental remediation liabilities
Current (in accrued liabilities), Environmental Remediation	27	27
Long-term, Environmental Remediation	211	213
Total, Environmental Remediation	$ 238	$ 240