Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)		12 Months Ended
	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Summary Of Significant Accounting Policies [Line Items]
Annual aggregate depreciation allowance	$ 1,110,000,000	$ 1,110,000,000
Impairment charges			$ 0	$ 0
Revenue deferral period (months)		12 months
Investment gains and losses recognized, time period (years)		15 years
Other actuarial gains and losses recognized, time period (years)		10 years
Difference between fair value and expected market related value of plan assets (percent)		20.00%
Non Utility Plan | Minimum
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives (years)		3 years
Non Utility Plan | Maximum
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives (years)		30 years
CECONY
Summary Of Significant Accounting Policies [Line Items]
AFUDC rates (percent)		4.40%	1.60%	4.00%
Average depreciation rates (percent)		3.10%	3.10%	3.20%
Annual aggregate depreciation allowance	1,050,000,000	$ 1,050,000,000
CECONY | Electric | Minimum
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives (years)		5 years
CECONY | Electric | Maximum
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives (years)		85 years
CECONY | Gas | Minimum
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives (years)		5 years
CECONY | Gas | Maximum
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives (years)		85 years
CECONY | Steam | Minimum
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives (years)		5 years
CECONY | Steam | Maximum
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives (years)		80 years
CECONY | General Plant | Minimum
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives (years)		5 years
CECONY | General Plant | Maximum
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives (years)		55 years
O&R
Summary Of Significant Accounting Policies [Line Items]
AFUDC rates (percent)		0.40%	2.60%	5.70%
Average depreciation rates (percent)		3.00%	2.90%	2.80%
O&R | Electric | Minimum
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives (years)		5 years
O&R | Electric | Maximum
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives (years)		75 years
O&R | Gas | Minimum
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives (years)		5 years
O&R | Gas | Maximum
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives (years)		75 years
O&R | General Plant | Minimum
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives (years)		5 years
O&R | General Plant | Maximum
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives (years)		50 years
Discontinued Operations, Held-for-sale | Pike
Summary Of Significant Accounting Policies [Line Items]
Impairment charge on assets held for sale	$ 5,000,000	$ 5,000,000