Acquisitions and Dispositions (Details)	1 Months Ended		3 Months Ended
	Feb. 09, 2012 USD ($) MW	Feb. 09, 2012 EUR (€)	Sep. 30, 2012 USD ($)	Jun. 30, 2012 USD ($)	Dec. 31, 2012 Purchase Price Allocation Preliminary [Member] USD ($)	Dec. 31, 2012 Purchase Price Allocation Adjustments [Member] USD ($)	Dec. 31, 2012 Purchase Price Allocation Adjustments [Member] Property, plant and equipment [Member] USD ($)	Dec. 31, 2012 Purchase Price Allocation Adjustments [Member] Intangible assets subject to amortization [Member] USD ($)	Dec. 31, 2012 Purchase Price Allocation Adjustments [Member] Regulatory Assets [Member] USD ($)	Dec. 31, 2012 Purchase Price Allocation Adjustments [Member] Out of market coal contract [Member] USD ($)	Dec. 31, 2012 Purchase Price Allocation Adjustments [Member] Finalization of entity's standalone federal tax return [Member] USD ($)	Dec. 31, 2012 Purchase Price Allocation Updated [Member] USD ($)	Apr. 20, 2011 DPL Acquisition [Member] USD ($)
Acquisitions [Line Items]
Business Acquisition, Cost of Acquired Entity, Purchase Price													$ 3,500,000,000
Business Acquisition, Percentage of Voting Interests Acquired													100.00%
Purchase Price Allocation
Cash					116,000,000	0						116,000,000
Accounts receivable					278,000,000	0						278,000,000
Inventory					124,000,000	0						124,000,000
Other current assets					41,000,000	0						41,000,000
Property, plant and equipment					2,549,000,000	(71,000,000)						2,478,000,000
Intangible assets subject to amortization					166,000,000	(19,000,000)						147,000,000
Intangible assets - indefinite-lived					5,000,000	0						5,000,000
Regulatory assets					201,000,000	16,000,000						217,000,000
Other noncurrent assets					58,000,000	0						58,000,000
Current liabilities					(401,000,000)	(5,000,000)						(406,000,000)
Non-recourse debt					(1,255,000,000)	0						(1,255,000,000)
Deferred taxes					(558,000,000)	7,000,000	25,000,000	7,000,000	(21,000,000)	12,000,000	(16,000,000)	(551,000,000)
Regulatory liabilities					(117,000,000)	0						(117,000,000)
Other noncurrent liabilities					(195,000,000)	(15,000,000)				(29,000,000)	13,000,000	(210,000,000)
Redeemable preferred stock					(18,000,000)	0						(18,000,000)
Net identifiable assets acquired					994,000,000	(87,000,000)						907,000,000
Goodwill					2,489,000,000	87,000,000						2,576,000,000
Net assets acquired					3,483,000,000	0						3,483,000,000
Dispositions
Cartagena ownership interest sold	80.00%	80.00%
Cartagena generation capacity (MW)	1,199	1,199
Cartagena ownership interest prior to sale	70.81%	70.81%
Proceeds from sale of ownership interest in Cartagena	229,000,000	172,000,000
Price to exercise option to purchase remaining interest of Cartagena	37,000,000	28,000,000
Amount recovered by Cartagena from GDF	95,000,000	71,000,000
Proceeds received on the settlement with GDF	38,000,000	28,000,000
Gain on sale of Cartagena	178,000,000
Deferred gain on sale of Cartagena	9,000,000
Proceeds from sale of St. Patrick and InnoVent				42,000,000
Proceeds from sale of China equity method investments			133,000,000
Gain on sale of China equity method investments			$ 27,000,000