Discontinued Operations And Held-For-Sale Businesses (Details) $ in Millions			1 Months Ended		3 Months Ended		6 Months Ended			7 Months Ended	12 Months Ended
	Feb. 24, 2014 USD ($)	Jan. 30, 2014 USD ($)	Jun. 30, 2014 USD ($)	Nov. 30, 2013 USD ($) project MW	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)		Mar. 31, 2014 USD ($)	Jun. 30, 2015 USD ($) business	Sep. 30, 2014 business	Oct. 30, 2013 MW	Sep. 30, 2013
Discontinued Operations Income Loss
Revenue					$ 0	$ 104	$ 0	$ 233	[1]
Income from operations of discontinued businesses, before income tax					0	15	0	49	[1]
Income tax expense					0	(8)	0	(22)	[1]
Income from operations of discontinued businesses, after income tax					0	7	0	27	[1]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of businesses classified as discontinued operations after adoption of new accounting standard | business											0
Impairment expenses							45	273
Net loss from disposal and impairments of discontinued businesses					0	(13)	0	(56)	[1]
Sonel [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Sale of ownership in subsidiary percent														56.00%
Kribi [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Sale of ownership in subsidiary percent														56.00%
Dibamba [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Sale of ownership in subsidiary percent														56.00%
Cameroon [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Impairment expenses										$ 101
Carrying amount			$ 435			435		435
Fair value less costs to sell			334			334		334
Saurashtra [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Net proceeds received from sale of businesses	$ 8
Generation Capacity Mega Watts | MW													39
US Wind Projects [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Sale of ownership in subsidiary percent				100.00%
Net proceeds received from sale of businesses		$ 27
Generation Capacity Mega Watts | MW				234
Number of wind projects | project				3
Deferred proceeds from divestiture of businesses		$ 3
Armenia Mountain [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Gross Profit (Loss)					2	2	6	5
Cameroon [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Number of Equity Interests Sold | business												3
Disposal Group, Including Discontinued Operation, Consideration			200			200		200
Letter of Credit Related to Sale Agreement			40			40		40
Net proceeds received from sale of businesses			156
Net loss from disposal and impairments of discontinued businesses						(7)
Armenia Mountain [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Generation Capacity Mega Watts | MW				101
Buyer option to purchase ownership percent				100.00%
Buyer option to purchase ownership interest, sales price				$ 75
Noncurrent Asset [Member] | Cameroon [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Non-contingent Consideration, Fair Value, Amount to be Received			$ 44			$ 44		$ 44
Carrying amount					$ 44		$ 44				$ 44

[1] Three Months Ended June 30, Six Months Ended June 30, 2015 2014 2015 2014 (in millions)Revenue$— $104 $— $233Income from operations of discontinued businesses, before income tax$— $15 $— $49Income tax expense— (8) — (22)Income from operations of discontinued businesses, after income tax$— $7 $— $27Net loss from disposal & impairments of discontinued businesses, after income tax$— $(13) $— $(56)