Capitalization - Additional Information (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($)
Level 2
Schedule of Capitalization [Line Items]
Long-term debt, fair value	$ 16,752
Level 3
Schedule of Capitalization [Line Items]
Long-term debt, fair value	636
CECONY | Level 2
Schedule of Capitalization [Line Items]
Long-term debt, fair value	13,864
CECONY | Level 3
Schedule of Capitalization [Line Items]
Long-term debt, fair value	636
Tax-exempt debt	$ 636