Unaudited Quarterly Operating Results (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013
Unaudited Quarterly Operating Results [Abstract]
Electric Domestic Operating Revenue, Quarterly	$ 190	$ 233	$ 179	$ 177	$ 187	$ 213	$ 175	$ 172
Gas Domestic Operating Revenue, Quarterly	42	18	21	44	32	14	20	40
Operating Income (loss), Quarterly	41	60	31	46	3	58	30	49
Net Income (Loss) Attributable to Parent, Quarterly	$ 20	$ 31	$ 14	$ 22	$ (7)	$ 29	$ 11	$ 22