Stock-Based Compensation - Summary of Changes in Status of Time-Based Awards (Details) - Time-based Awards	12 Months Ended
	Dec. 31, 2017 $ / shares shares
Units
Non-vested at beginning of period (in shares) | shares	65,980
Granted (in shares) | shares	23,000
Vested (in shares) | shares	(21,359)
Forfeited (in shares) | shares	(2,751)
Non-vested at end of period (in shares) | shares	64,870
Weighted Average Grant Date Fair Value
Non-vested at beginning of period (in dollars per share) | $ / shares	$ 64.04
Granted (in dollars per share) | $ / shares	77.66
Vested (in dollars per share) | $ / shares	53.77
Forfeited (in dollars per share) | $ / shares	71.62
Non-vested at end of period (in dollars per share) | $ / shares	$ 71.93
CECONY
Units
Non-vested at beginning of period (in shares) | shares	62,580
Granted (in shares) | shares	21,800
Vested (in shares) | shares	(20,359)
Forfeited (in shares) | shares	(2,601)
Non-vested at end of period (in shares) | shares	61,420
Weighted Average Grant Date Fair Value
Non-vested at beginning of period (in dollars per share) | $ / shares	$ 64.03
Granted (in dollars per share) | $ / shares	77.66
Vested (in dollars per share) | $ / shares	53.77
Forfeited (in dollars per share) | $ / shares	71.93
Non-vested at end of period (in dollars per share) | $ / shares	$ 71.93