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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Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

+ References

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This item represents an other than temporary decline in value that has been recognized against an investment accounted for under the cost method of accounting. The excess of the carrying amount over the fair value of the investment represents the amount of the write down which is or was reflected in earnings. The written down value is a new cost basis with the adjusted value of the investment becoming its new carrying value. Evidence of a loss in value might include, but would not necessarily be limited to, absence of an ability to recover the carrying amount of the investment or inability of the investee to sustain an earnings capacity which would justify the carrying amount of the investment.

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This item represents an other than temporary decline in value that has been recognized against an investment accounted for under the equity method of accounting. The excess of the carrying amount over the fair value of the investment represents the amount of the write down which is or was reflected in earnings. The written down value is a new cost basis with the adjusted value of the investment becoming its new carrying value subject to the equity accounting method. Evidence of a loss in value might include, but would not necessarily be limited to, absence of an ability to recover the carrying amount of the investment or inability of the investee to sustain an earnings capacity which would justify the carrying amount of the investment.

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Gain (loss) from sale or disposal of an organization or integrated set of activities (for example, but not limited to, a partnership or corporation) engaged in providing a product or service in a commercial, industrial, or professional environment.

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Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

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The aggregate amount of asset impairment charges other than goodwill impairment, gains and losses related to the divestiture of businesses, and unusual items incurred during an accounting period. Generally, these items are either unusual or infrequent, but not both (in which case they would be extraordinary items).

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Income expense from divestitures asset impairments and unusual items.

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Asset Impairments and Unusual Items - Summary (Detail) - USD ($) $ in Millions	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Jun. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Income Expense From Divestitures Asset Impairments And Unusual Items [Line Items]
Expense from divestitures, asset impairments and unusual items, net	$ 9	$ 106		$ 10	$ 107
Western Pennsylvania [Member]
Income Expense From Divestitures Asset Impairments And Unusual Items [Line Items]
Asset impairments					43
LampTracker Reporting Unit [Member]
Income Expense From Divestitures Asset Impairments And Unusual Items [Line Items]
Goodwill impairment charges					10
Waste Diversion Technology Companies [Member]
Income Expense From Divestitures Asset Impairments And Unusual Items [Line Items]
Equity method investments impairment charges				28
Cost method investment impairment			$ 41
Investment In Majority Owned Organics Company [Member]
Income Expense From Divestitures Asset Impairments And Unusual Items [Line Items]
Loss on sale of business					8
San Jacinto Waste Pits [Member]
Income Expense From Divestitures Asset Impairments And Unusual Items [Line Items]
Revisions in estimate	$ 9			$ 9	$ 42	$ 44