Revenue Recognition (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenue Recognition and Deferred Revenue [Abstract]
Residential	$ 207		$ 475
Commercial	162		313
Industrial	39		83
Direct access customers	13		23
Subtotal	421		894
Alternative revenue programs, net of amortization	0	$ 0	(2)	$ 0
Other accrued (deferred) revenues, net	(10)		(27)
Total retail revenues	411		865
Wholesale Revenues	24		52
Other operating revenues	14		25
Total Revenues	449	$ 449	942	$ 979
Net tax benefits due to the change in tax rate under the TCJA	10		25
Gain on Derivative Instruments, Pretax	$ 4		$ 6