Landfill and Environmental Remediation Liabilities - Summary (Detail) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Landfill and environmental remediation liabilities
Total, Environmental Remediation	$ 216
Current (in accrued liabilities)	161	$ 164
Long-term	2,345	2,222
Total	2,506	2,386
Landfill [Member]
Landfill and environmental remediation liabilities
Current (in accrued liabilities), Landfill	135	138
Long-term, Landfill	2,155	2,018
Total, Landfill	2,290	2,156
Environmental Remediation Liabilities [Member]
Landfill and environmental remediation liabilities
Current (in accrued liabilities), Environmental Remediation	26	26
Long-term, Environmental Remediation	190	204
Total, Environmental Remediation	$ 216	$ 230