Summary of Significant Accounting Policies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013 Y	Dec. 31, 2012	Dec. 31, 2011
Summary Of Significant Accounting Policies [Line Items]
Annual aggregate depreciation allowance	$ 948
Impairment charges	0	0	0
Investment gains and losses recognized, time period, years	15
Other actuarial gains and losses recognized, time period, years	10
Difference between fair value and expected Market Related Value of plan assets	20.00%
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives,(years)	3 years
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives,(years)	30 years
CECONY [Member]
Summary Of Significant Accounting Policies [Line Items]
AFDC rates	4.00%	6.50%	6.90%
Average depreciation rate	3.20%	3.10%	3.10%
Annual aggregate depreciation allowance	$ 897
CECONY [Member] | Electric [Member] | Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives,(years)	5 years
CECONY [Member] | Electric [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives,(years)	80 years
CECONY [Member] | Gas [Member] | Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives,(years)	5 years
CECONY [Member] | Gas [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives,(years)	85 years
CECONY [Member] | Steam [Member] | Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives,(years)	5 years
CECONY [Member] | Steam [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives,(years)	70 years
CECONY [Member] | General [Member] | Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives,(years)	5 years
CECONY [Member] | General [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives,(years)	50 years
O&R [Member]
Summary Of Significant Accounting Policies [Line Items]
AFDC rates	5.70%	7.00%	6.60%
Average depreciation rate	2.80%	2.90%	2.80%
O&R [Member] | Electric [Member] | Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives,(years)	5 years
O&R [Member] | Electric [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives,(years)	75 years
O&R [Member] | Gas [Member] | Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives,(years)	5 years
O&R [Member] | Gas [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives,(years)	75 years
O&R [Member] | General [Member] | Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives,(years)	5 years
O&R [Member] | General [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives,(years)	50 years