Other Material Contingencies - Additional Information (Detail) (USD $)	1 Months Ended	6 Months Ended
	Jul. 31, 2007 Person	Jun. 30, 2014 Guarantee Entity Lawsuits	Dec. 31, 2013
Operating Leased Assets [Line Items]
Number of person died in steam ruptured	1
Number of suits pending against the company		90
Insurance receivable for suits		$ 50,000,000
Description of explosion and fire incident		On March 12, 2014, two multi-use five-story tall buildings located on Park Avenue between 116th and 117th Street in Manhattan were destroyed by an explosion and fire. CECONY had delivered gas to the buildings through service lines from a distribution main located below ground on Park Avenue. Eight people died and more than 48 people were injured. Additional buildings were also damaged.
Guarantee obligations maximum exposure		1,428,000,000	1,331,000,000
Number of entities		2
Number of guaranteed payments		2
Other [Member]
Operating Leased Assets [Line Items]
Guarantee obligations maximum exposure		31,000,000
Estimate of maximum potential obligation		5,000,000
Indemnity agreements amount		25,000,000
Con Edison Development [Member]
Operating Leased Assets [Line Items]
Percentage of variable interests		50.00%
Con Edison Development [Member] | Guarantee One [Member]
Operating Leased Assets [Line Items]
Guarantee obligations maximum exposure		80,000,000
Con Edison Development [Member] | Guarantee Two [Member]
Operating Leased Assets [Line Items]
Guarantee obligations maximum exposure		120,000,000
Construction and Operation of Solar Energy Facilities [Member]
Operating Leased Assets [Line Items]
Guarantees issued		3,000,000
Insurance Receivable [Member]
Operating Leased Assets [Line Items]
Estimated accrued liability for suits		$ 50,000,000