Income Tax - Schedule of Components of Income Tax (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
State
Current	$ (42)	$ 38	$ 59
Deferred	188	93	61
Federal
Current	(43)	(86)	(9)
Deferred	604	569	463
Amortization of investment tax credits	(9)	(9)	(6)
Total income tax expense	698	605	568
CECONY
State
Current	(1)	48	66
Deferred	114	82	65
Federal
Current	59	77	158
Deferred	435	372	271
Amortization of investment tax credits	(4)	(5)	(5)
Total income tax expense	$ 603	$ 574	$ 555