Fair Value (Nonrecurring Unobservable Inputs) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013 Poland Wind Projects [Member]	Sep. 30, 2013 Itabo (San Lorenzo) [Member]		Sep. 30, 2013 Discounted cash flow [Member] Long Lived Assets Held And Used [Member] Beaver Valley [Member]	Sep. 30, 2013 Discounted cash flow [Member] Equity Method Affiliate [Member] Elsta [Member]	Sep. 30, 2013 Discounted cash flow [Member] Minimum [Member] Long Lived Assets Held And Used [Member] Beaver Valley [Member]	Sep. 30, 2013 Discounted cash flow [Member] Minimum [Member] Equity Method Affiliate [Member] Elsta [Member]	Sep. 30, 2013 Discounted cash flow [Member] Maximum [Member] Long Lived Assets Held And Used [Member] Beaver Valley [Member]	Sep. 30, 2013 Discounted cash flow [Member] Maximum [Member] Equity Method Affiliate [Member] Elsta [Member]	Sep. 30, 2013 Discounted cash flow [Member] Weighted Average [Member] Long Lived Assets Held And Used [Member] Beaver Valley [Member]	Sep. 30, 2013 Discounted cash flow [Member] Weighted Average [Member] Equity Method Affiliate [Member] Elsta [Member]	Sep. 30, 2013 Market Approach [Member] Long Lived Assets Held And Used [Member] Poland Wind Projects [Member]	Sep. 30, 2013 Market Approach [Member] Long Lived Assets Held And Used [Member] Itabo (San Lorenzo) [Member]	Sep. 30, 2013 Fair Value [Member] Level 3 [Member]	Sep. 30, 2013 Fair Value [Member] Level 3 [Member] Long Lived Assets Held And Used [Member] Beaver Valley [Member]		Sep. 30, 2013 Fair Value [Member] Level 3 [Member] Long Lived Assets Held And Used [Member] Poland Wind Projects [Member]		Sep. 30, 2013 Fair Value [Member] Level 3 [Member] Long Lived Assets Held And Used [Member] Itabo (San Lorenzo) [Member]		Sep. 30, 2012 Fair Value [Member] Level 3 [Member] Equity Method Affiliate [Member]	Sep. 30, 2013 Fair Value [Member] Level 3 [Member] Equity Method Affiliate [Member] Elsta [Member]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Fair Value, Nonrecurring	$ 14	$ 7	[1]											$ 154	$ 15	[1]	$ 14	[1]	$ 7	[1]	$ 0	$ 118	[2]
Annual Revenue Growth Input						3.00%	(55.00%)	45.00%	17.00%	19.00%	1.00%
Pretax Operating Margin Input						(42.00%)	3.00%	41.00%	45.00%	25.00%	36.00%
Weighted Average Cost Of Capital Input				7.00%	7.00%
Indicative Offer Prices												14
Broker Quote													$ 7

[1] See Note 14 — Asset Impairment Expense for further information.

[2] See Note 15 — Other Non-Operating Expense for further information.