Mergers, Acquisitions and Dispositions Purchase Price allocation Table - Con Edison (Details) - USD ($) $ in Millions		12 Months Ended
	Sep. 01, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Combination Segment Allocation [Line Items]
Payments to Acquire Businesses, Gross		$ 208	$ 6,934	$ 40
ConEdison Solutions [Member]
Business Combination Segment Allocation [Line Items]
Payments to Acquire Businesses, Gross	$ 257
BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedWorkingCapital	204
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment	2
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Financial Assets	6
BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedEnergyContract	100
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Indefinite-Lived Intangible Assets	9
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Other	1
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets	322
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Financial Liabilities	65
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities	65
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net	$ 257