Percentage of voting equity interests acquired at the acquisition date in the business combination.

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Cost of oil and gas purchased during the reporting period.

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Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

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The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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The parent entity's interest in net assets of the subsidiary, expressed as a percentage.

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For an unclassified balance sheet, amounts due from parties associated with the reporting entity as evidenced by a written promise to pay.

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Related Party Transactions (Details) - USD ($) $ in Millions	3 Months Ended		4 Months Ended	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2016	Sep. 30, 2015	Oct. 31, 2016	Jun. 30, 2016	May 31, 2016	Jan. 31, 2016	Dec. 31, 2014
Related Party Transaction [Line Items]
Ownership interest, percentage										45.70%
Costs of gas purchased	$ 81	$ 64		$ 320	$ 415
Loss on derivative	77	52		163	134
CECONY \| Financial Electric Capacity Contract
Related Party Transaction [Line Items]
Loss on derivative	1			1
CECONY
Related Party Transaction [Line Items]
Costs of gas purchased	34	$ 30		217	$ 282
CET Electric
Related Party Transaction [Line Items]
Ownership interest, percentage								45.70%	45.70%
Stagecoach Gas Services LLC
Related Party Transaction [Line Items]
Equity method ownership (percent)							50.00%
Stagecoach Gas Services LLC \| CECONY \| Equity Method Investee \| Purchased Power Costs
Related Party Transaction [Line Items]
Costs of gas purchased	10		$ 8
Panoche Valley \| Equity Method Investee
Related Party Transaction [Line Items]
Notes receivable from related parties	$ 234		$ 234	$ 234
Equity method ownership (percent)	50.00%		50.00%	50.00%
California \| Scenario, Forecast \| Panoche Valley
Related Party Transaction [Line Items]
Voting interest acquired (percentage)						50.00%
California \| Scenario, Forecast \| Panoche Valley
Related Party Transaction [Line Items]
Voting interest acquired (percentage)						50.00%