Stock-Based Compensation - Summary of Stock Options (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Aggregate intrinsic value
Options outstanding	$ 0	$ 2
Options exercised	2	3
Cash received by Con Edison for payment of exercise price	3	6
CECONY
Aggregate intrinsic value
Options outstanding	0	1
Options exercised	2	3
Cash received by Con Edison for payment of exercise price	$ 3	$ 5