Regulatory Matters - Summary of Utilities Rate Plans (CECONY-Steam) (Details) - USD ($)	12 Months Ended			36 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2016
Public Utilities, General Disclosures [Line Items]
Cost reconciliation, deferred net regulatory liabilities	$ 986,000,000	$ 947,000,000		$ 986,000,000
Cost reconciliations, deferred net regulatory assets	822,000,000	836,000,000		822,000,000
CECONY
Public Utilities, General Disclosures [Line Items]
Cost reconciliation, deferred net regulatory liabilities	940,000,000	899,000,000		940,000,000
Cost reconciliations, deferred net regulatory assets	728,000,000	752,000,000		728,000,000
CECONY | Steam
Public Utilities, General Disclosures [Line Items]
Negative revenue adjustments	0	0	$ 0
Cost reconciliation, deferred net regulatory liabilities	$ 8,000,000		42,000,000	$ 8,000,000
Cost reconciliations, deferred net regulatory assets		17,000,000
Deferred regulatory liability (reduction)			100,000
Authorized return on common equity (percent)				9.30%
Earnings sharing (percentage)	9.90%			9.90%
Earnings sharing, threshold limit	$ 7,800,000	$ 11,500,000	$ 0
Common equity ratio (percent)				48.00%
Other regulatory liabilities	$ 8,000,000			$ 8,000,000
Difference in property taxes (percent)	90.00%
Deferral, annual maximum (not more than) (percent)	0.10%
CECONY | Steam | Year 1
Public Utilities, General Disclosures [Line Items]
Base rate changes				(22,400,000)
Amortization to income of net regulatory (assets) and liabilities				37,000,000
Average rate base				$ 1,511,000,000
Weighted average cost of capital (after-tax) (percent)				7.10%
Cost of long-term debt (percent)	5.17%			5.17%
CECONY | Steam | Year 1 | Production
Public Utilities, General Disclosures [Line Items]
Deferred regulatory liability (reduction)				$ 1,752,000,000
CECONY | Steam | Year 1 | Distribution
Public Utilities, General Disclosures [Line Items]
Deferred regulatory liability (reduction)				6,000,000
CECONY | Steam | Year 1 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)				1,000,000
CECONY | Steam | Year 2
Public Utilities, General Disclosures [Line Items]
Base rate changes				19,800,000
Amortization to income of net regulatory (assets) and liabilities				37,000,000
Average rate base				$ 1,547,000,000
Weighted average cost of capital (after-tax) (percent)				7.13%
Cost of long-term debt (percent)	5.23%			5.23%
CECONY | Steam | Year 2 | Production
Public Utilities, General Disclosures [Line Items]
Deferred regulatory liability (reduction)				$ 1,732,000,000
CECONY | Steam | Year 2 | Distribution
Public Utilities, General Disclosures [Line Items]
Deferred regulatory liability (reduction)				11,000,000
CECONY | Steam | Year 2 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)				1,000,000
CECONY | Steam | Year 3
Public Utilities, General Disclosures [Line Items]
Base rate changes				20,300,000
Amortization to income of net regulatory (assets) and liabilities				37,000,000
Average rate base				$ 1,604,000,000
Weighted average cost of capital (after-tax) (percent)				7.21%
Cost of long-term debt (percent)	5.39%			5.39%
CECONY | Steam | Year 3 | Production
Public Utilities, General Disclosures [Line Items]
Deferred regulatory liability (reduction)				$ 1,720,000,000
CECONY | Steam | Year 3 | Distribution
Public Utilities, General Disclosures [Line Items]
Deferred regulatory liability (reduction)				25,000,000
CECONY | Steam | Year 3 | Maximum
Public Utilities, General Disclosures [Line Items]
Potential penalties (annually)				1,000,000
CECONY | Steam | Year 4
Public Utilities, General Disclosures [Line Items]
Base rate changes				$ 0