Fair Value (Nonrecurring Measurements) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset impairment expense	$ 0		$ 18		$ 48		$ 28
Long Lived Assets Held And Used [Member] | Beaver Valley [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset impairment expense					46	[1]
Long Lived Assets Held And Used [Member] | Kelanitissa [ Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset impairment expense							12	[1]
Long Lived Assets Held For Sale [Member] | Wind turbines [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset impairment expense					0	[1]
Long Lived Assets Held For Sale [Member] | St. Patrick [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset impairment expense							11	[1]
Discontinued operations and held for sale businesses [Member] | Ukraine utilities [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset impairment expense					34	[2]
Equity Method Affiliate [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Asset impairment expense							50	[3]
Carrying Amount [Member] | Long Lived Assets Held And Used [Member] | Beaver Valley [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	61	[1]			61	[1]
Carrying Amount [Member] | Long Lived Assets Held And Used [Member] | Kelanitissa [ Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring			22	[1]			22	[1]
Carrying Amount [Member] | Long Lived Assets Held For Sale [Member] | Wind turbines [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	25	[1]			25	[1]
Carrying Amount [Member] | Long Lived Assets Held For Sale [Member] | St. Patrick [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring			33	[1]			33	[1]
Carrying Amount [Member] | Discontinued operations and held for sale businesses [Member] | Ukraine utilities [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	143	[2]			143	[2]
Carrying Amount [Member] | Equity Method Affiliate [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring			205	[3]			205	[3]
Fair Value [Member] | Long Lived Assets Held And Used [Member] | Beaver Valley [Member] | Level 1 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	0	[1]			0	[1]
Fair Value [Member] | Long Lived Assets Held And Used [Member] | Beaver Valley [Member] | Level 2 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	0	[1]			0	[1]
Fair Value [Member] | Long Lived Assets Held And Used [Member] | Beaver Valley [Member] | Level 3 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	15	[1]			15	[1]
Fair Value [Member] | Long Lived Assets Held And Used [Member] | Kelanitissa [ Member] | Level 1 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring			0	[1]			0	[1]
Fair Value [Member] | Long Lived Assets Held And Used [Member] | Kelanitissa [ Member] | Level 2 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring			0	[1]			0	[1]
Fair Value [Member] | Long Lived Assets Held And Used [Member] | Kelanitissa [ Member] | Level 3 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring			10	[1]			10	[1]
Fair Value [Member] | Long Lived Assets Held For Sale [Member] | Wind turbines [Member] | Level 1 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	0	[1]			0	[1]
Fair Value [Member] | Long Lived Assets Held For Sale [Member] | Wind turbines [Member] | Level 2 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	25	[1]			25	[1]
Fair Value [Member] | Long Lived Assets Held For Sale [Member] | St. Patrick [Member] | Level 1 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring			0	[1]			0	[1]
Fair Value [Member] | Long Lived Assets Held For Sale [Member] | St. Patrick [Member] | Level 2 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring			22	[1]			22	[1]
Fair Value [Member] | Long Lived Assets Held For Sale [Member] | St. Patrick [Member] | Level 3 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring			0	[1]			0	[1]
Fair Value [Member] | Discontinued operations and held for sale businesses [Member] | Ukraine utilities [Member] | Level 1 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	0	[2]			0	[2]
Fair Value [Member] | Discontinued operations and held for sale businesses [Member] | Ukraine utilities [Member] | Level 2 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	113	[2]			113	[2]
Fair Value [Member] | Discontinued operations and held for sale businesses [Member] | Ukraine utilities [Member] | Level 3 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring	0	[2]			0	[2]
Fair Value [Member] | Equity Method Affiliate [Member] | Level 1 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring			0	[3]			0	[3]
Fair Value [Member] | Equity Method Affiliate [Member] | Level 2 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring			155	[3]			155	[3]
Fair Value [Member] | Equity Method Affiliate [Member] | Level 3 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Abstract]
Fair Value, Nonrecurring			$ 0	[3]			$ 0	[3]

[1] See Note 13 — Asset Impairment Expense for further information.

[2] See Note 14 — Discontinued Operations and Held For Sale Businesses for further information. Also, the gross loss equals the carrying amount of the disposal group less its fair value less costs to sell.

[3] .