Intangible Assets (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013
Intangible Assets (Textuals) [Abstract]
Intangible Assets, Gross	$ 1,017
Intangible Assets, Accumulated Amortization	429
Intangible Assets, Net	588
Amortization Expense
Actual, 2013	100
Estimated, 2014	80
Estimated, 2015	75
Estimated, 2016	75
Estimated, 2017	69
Estimated, 2018	51
Estimated, Thereafter	185
NUG contracts
Intangible Assets (Textuals) [Abstract]
Intangible Assets, Gross	124	[1],[2]
Intangible Assets, Accumulated Amortization	15	[1],[2]
Intangible Assets, Net	109	[1],[2]
Amortization Expense
Actual, 2013	5	[1],[2]
Estimated, 2014	5	[1],[2]
Estimated, 2015	5	[1],[2]
Estimated, 2016	5	[1],[2]
Estimated, 2017	5	[1],[2]
Estimated, 2018	5	[1],[2]
Estimated, Thereafter	84	[1],[2]
OVEC
Intangible Assets (Textuals) [Abstract]
Intangible Assets, Gross	54	[1]
Intangible Assets, Accumulated Amortization	5	[1]
Intangible Assets, Net	49	[1]
Amortization Expense
Actual, 2013	2	[1]
Estimated, 2014	2	[1]
Estimated, 2015	2	[1]
Estimated, 2016	2	[1]
Estimated, 2017	2	[1]
Estimated, 2018	2	[1]
Estimated, Thereafter	39	[1]
Coal contracts
Intangible Assets (Textuals) [Abstract]
Intangible Assets, Gross	556	[1],[3]
Intangible Assets, Accumulated Amortization	222	[1],[3]
Intangible Assets, Net	334	[1],[3]
Amortization Expense
Actual, 2013	62	[1],[3]
Estimated, 2014	55	[1],[3]
Estimated, 2015	51	[1],[3]
Estimated, 2016	51	[1],[3]
Estimated, 2017	45	[1],[3]
Estimated, 2018	30	[1],[3]
Estimated, Thereafter	49	[1],[3]
Coal contracts | Recorded with Regulatory Offset
Intangible Assets (Textuals) [Abstract]
Intangible Assets, Gross	102
Intangible Assets, Net	53
Customer Contracts
Intangible Assets (Textuals) [Abstract]
Intangible Assets, Gross	147
Intangible Assets, Accumulated Amortization	52
Intangible Assets, Net	95
Amortization Expense
Actual, 2013	17
Estimated, 2014	17
Estimated, 2015	17
Estimated, 2016	17
Estimated, 2017	17
Estimated, 2018	14
Estimated, Thereafter	13
Energy contracts
Intangible Assets (Textuals) [Abstract]
Intangible Assets, Gross	136	[1]
Intangible Assets, Accumulated Amortization	135	[1]
Intangible Assets, Net	1	[1]
Amortization Expense
Actual, 2013	14	[1]
Estimated, 2014	1	[1]
Estimated, 2015	0	[1]
Estimated, 2016	0	[1]
Estimated, 2017	0	[1]
Estimated, 2018	0	[1]
Estimated, Thereafter	$ 0	[1]

[1] (1)Fair value measurements of intangible assets recorded in connection with the Allegheny merger (see Note 21, Merger).

[2] (2)NUG contracts are subject to regulatory accounting and their amortization does not impact earnings.

[3] (3)A gross amount of $102 million ($53 million, net) of the coal contracts was recorded with a regulatory offset and the amortization does not impact earnings.