Regulatory Matters - Orange and Rockland Utilities, Inc. - Electric - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Public Utilities, General Disclosures [Line Items]
Potential operational penalties	$ 1,389,000,000
Regulatory asset	7,201,000,000	9,705,000,000
O&R-Electric [Member]
Public Utilities, General Disclosures [Line Items]
Recognition of deferred expenses	4,100,000
Regulatory asset	1,100,000
Potential operational penalties	3,000,000
O&R-Electric [Member] | Maximum [Member]
Public Utilities, General Disclosures [Line Items]
Common equity ratio	50.00%
O&R-Electric [Member] | July 2008 [Member]
Public Utilities, General Disclosures [Line Items]
Annual return on common equity	9.40%		9.40%
Actual earnings on equity, percentage	10.20%
Average common equity ratio, subject to a 50 percent maximum	50.00%
Recognition of deferred expenses	0	0	300,000		3,000,000
Recognition of deferred revenue				700,000
Company deferred revenue			7,000,000	12,000,000	8,000,000
Annual inflation rate			4.00%
Potential negative earnings adjustments	3,000,000
Reduction in company revenue				1,000,000
Accrued revenue			3,300,000	5,100,000	12,500,000
O&R-Electric [Member] | May 2010 [Member]
Public Utilities, General Disclosures [Line Items]
Electric base rate increase	9,800,000
Annual return on common equity	10.30%
Common equity ratio	50.00%
O&R-Electric [Member] | November 2013 [Member]
Public Utilities, General Disclosures [Line Items]
Electric base rate increase	19,300,000
Annual return on common equity	10.25%
Common equity ratio	52.20%
Recovery cost	25,400,000
O&R-Electric [Member] | July 2011[Member]
Public Utilities, General Disclosures [Line Items]
Electric base rate increase	26,600,000
Annual return on common equity	9.20%
Weighted average cost of capital	7.22%
Austerity measures	825,000
Cost of long-term debt, percentage	5.50%
Common equity ratio	48.00%
Average net utility plant rates	718,000,000
Potential operational penalties	3,000,000
O&R-Electric [Member] | July 2008 [Member]
Public Utilities, General Disclosures [Line Items]
Electric base rate increase	15,600,000
O&R-Electric [Member] | July 2009 [Member]
Public Utilities, General Disclosures [Line Items]
Electric base rate increase	15,600,000
O&R-Electric [Member] | July 2010 [Member]
Public Utilities, General Disclosures [Line Items]
Electric base rate increase	5,700,000
Collection of additional electric cost	9,900,000
O&R-Electric [Member] | July 2012 [Member]
Public Utilities, General Disclosures [Line Items]
Electric base rate increase	19,400,000
Increase rate	15,200,000
O&R-Electric [Member] | July 2013 [Member]
Public Utilities, General Disclosures [Line Items]
Electric base rate increase	8,800,000
Increase rate	15,200,000
O&R-Electric [Member] | July 2014 [Member]
Public Utilities, General Disclosures [Line Items]
Electric base rate increase	15,200,000
Increase rate	13,100,000
Surcharge payment	2,100,000
O&R-Electric [Member] | June 30, 2013 [Member]
Public Utilities, General Disclosures [Line Items]
Annual return on common equity	9.40%
Weighted average cost of capital	7.61%
Common equity ratio	48.00%
Average net utility plant rates	678,000,000
Cost of long-term debt	6.07%
Average base rate	671,000,000
Percentage of revenue allocated to customers	50.00%
Common equity basis points	80
O&R-Electric [Member] | June 30, 2014 [Member]
Public Utilities, General Disclosures [Line Items]
Annual return on common equity	9.50%
Weighted average cost of capital	7.65%
Common equity ratio	48.00%
Average net utility plant rates	704,000,000
Cost of long-term debt	6.07%
Average base rate	708,000,000
Percentage of revenue allocated to customers	75.00%
Common equity basis points	180
O&R-Electric [Member] | June 30, 2015 [Member]
Public Utilities, General Disclosures [Line Items]
Annual return on common equity	9.60%
Weighted average cost of capital	7.48%
Common equity ratio	48.00%
Average net utility plant rates	753,000,000
Cost of long-term debt	5.64%
Average base rate	$ 759,000,000
Percentage of revenue allocated to customers	90.00%
Common equity basis points	280