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Landfill and Environmental Remediation Liabilities - Changes (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Landfill and environmental remediation liabilities
Interest accretion	$ 95	$ 92	$ 91
Ending balance, environmental remediation	237
Landfill [Member]
Landfill and environmental remediation liabilities
Beginning balance, landfill	1,675
Obligations incurred and capitalized	83
Obligations settled	(108)
Interest accretion	95
Revisions in estimates and interest rate assumptions	(3)
Acquisitions, divestitures and other adjustments	18
Ending balance, landfill	1,760	$ 1,675
Asset retirement obligation revision of estimate increase (decrease) related to estimated capping activities	12
Asset retirement obligation revision of estimate increase (decrease) related to annual review	$ (15)
Risk-free discount rate of the obligations	2.75%	2.50%	2.50%
Asset retirement obligation, increase (decrease) related to landfill acquisitions partially offset divestitures and other adjustments	$ 27
Environmental Remediation Liabilities [Member]
Landfill and environmental remediation liabilities
Beginning balance, environmental remediation	251
Obligations settled	(26)
Interest accretion	5
Revisions in estimates and interest rate assumptions	9
Acquisitions, divestitures and other adjustments	(2)
Ending balance, environmental remediation	$ 237	$ 251
Risk-free discount rate of the obligations	2.75%	2.50%
Increase (decrease) operating expenses due to change in discount rate	$ (3)

X

- Definition

Total costs accrued as of the balance sheet date for environmental loss contingencies.

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Amount of expense for newly incurred environmental loss contingencies. Includes, but is not limited to, remediation expense and interest accretion.

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Rate applied to the undiscounted amount of environmental loss contingencies to arrive at the present value recorded as of the balance sheet date.

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Amount of expense (reversal of expense) which increases (decreases) the accrual for environmental loss contingencies from revisions in estimates to existing obligations. Excludes changes related to business acquisitions, divestitures, or currency movement.

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The carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees.

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Amount of accretion expense recognized during the period that is associated with an asset retirement obligation. Accretion expense measures and incorporates changes due to the passage of time into the carrying amount of the liability.

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Amount of asset retirement obligations incurred during the period.

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Amount of asset retirement obligations settled, or otherwise disposed of, during the period. This may include asset retirement obligations transferred to third parties associated with the sale of a long-lived asset.

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Amount of increase (decrease) in the asset retirement obligation from changes in the amount or timing of the estimated cash flows associated with the settlement of the obligation.

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The amount of increase (decrease) due to landfill acquisitions partially offset by landfill divestitures and other adjustments.

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Represents the increase (decrease) included in the total revision of the asset retirement obligation during the period related to the increase (decrease) related to the year-end annual review of final capping, closure and post-closure obligations.

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Represents the increase (decrease) included in the total revision of the asset retirement obligation during the period related to the increase (decrease) related to the expected timing of capping activities.

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Increase (decrease) to operating expenses due to change in discount rate used to estimate present value of environmental remediation obligations.

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