Summary of Significant Accounting Policies - Landfill (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) site	Dec. 31, 2018 USD ($)	Dec. 31, 2017
Significant accounting policies
Receivables related to income tax payments in excess of our provision for income taxes	$ 231	$ 284
Federal Fuel Credits Receivable	70
Environmental remediation reasonably possible additional losses high estimate	140
Environmental remediation liabilities	240
Environmental remediation liabilities not subject to inflation or discounting	36	35
Increase of environmental remediation liability	$ 8	$ 3
Landfill [Member]
Significant accounting policies
Inflation rate	2.50%	2.50%	2.50%
Credit adjusted, risk free discount rate applicable to long-term asset retirement obligations	5.25%
Number of landfills sites with expansion | site	15
Number of expansion landfill sites require CFO approval inclusion of unpermitted airspace | site	1
Increase (decrease) in operating expenses	$ 9	$ (2)
Risk-free discount rate applied to environmental remediation liabilities and recovery assets	1.75%	2.75%	2.50%
Landfill [Member] | Minimum [Member]
Significant accounting policies
Permit application process period requirement	1 year
Landfill [Member] | Maximum [Member]
Significant accounting policies
Permit application process period requirement	5 years
Accounts Receivable Net [Member] | Concentration of Credit Risk [Member] | Maximum [Member]
Significant accounting policies
Concentration of risk threshold (as a percent)	5.00%	5.00%