Discontinued Operations and Held for sale businesses (Details) $ in Millions			1 Months Ended	3 Months Ended		6 Months Ended
		Jan. 30, 2014 USD ($)	Nov. 30, 2013 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)	Nov. 01, 2013 integer
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash Provided by (Used in) Operating Activities, Discontinued Operations						$ 57	$ (47)
Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax				$ (382)	$ 0	(382)	0
disposal group, not discontinued operations, available for purchase at option of acquirer		$ 3
Proceeds from sale of ownership interest						(134)	(461)
Discontinued Operation, Tax (Expense) Benefit from Provision for (Gain) Loss on Disposal						266
Disposal Group, Including Discontinued Operation, Assets, Noncurrent				0		0		$ 882
Expected future loss on disposal				700
Expected Cumulative impact of sale				1,100
Expected amounts of CTA to be reclassed as a result of sale				1,000		1,000
Expected reduction in Stockholders equity as a result of sale				100		100
Discontinued Operation, Tax Effect of Discontinued Operation				(1)	(3)	(3)	(7)
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent				(379)	(10)	(388)	(17)
Cash Provided by (Used in) Investing Activities, Discontinued Operations						(84)	7
US Wind Projects [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Noncontrolling Interest, Ownership Percentage by Parent									100.00%
Number of U.K. Wind Projects Sold | integer									3
Proceeds from sale of ownership interest		$ 27
Armenia Mountain [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sale Agreement, Buyer Option To Purchase Ownership Interest, Sales Price			$ 75
Sul Subsidiary [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Cash and Cash Equivalents				5		5		5
Disposal Group, Including Discontinued Operation, Prepaid and Other Assets				78		78		15
Disposal Group, Including Discontinued Operation, Revenue				219	202	419	428
Disposal Group, Including Discontinued Operation, Costs of Goods Sold				(204)	(203)	(408)	(428)
Impairment Expense Pre Tax Total				(783)	0	(783)	0
Disposal Group, Including Discontinued Operation, Other Expense				(11)	(12)	(20)	(24)
Disposal Group, Including Discontinued Operation, Assets, Noncurrent				1,600		1,600
Discontinued Operation, Income (Loss) from Discontinued Operation, before Income Tax				(779)	(13)	(792)	(24)
Discontinued Operation, Tax Effect of Discontinued Operation				400	3	404	7
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent				(379)	$ (10)	(388)	$ (17)
Disposal Group, Including Discontinued Operation, Accounts, Notes and Loans Receivable, Net				183		183		171
Disposal Group, Including Discontinued Operation, Property, Plant and Equipment				837		837		668
Disposal Group, Including Discontinued Operation, Deferred Tax Assets				594		594		133
Disposal Group, Including Discontinued Operation, Other Assets				188		188		218
Disposal group, loss recognized on classification as held for sale	[1]			(837)		(837)		0
Disposal Group, Including Discontinued Operation, Assets	[2]			1,048		1,048		1,306
Disposal Group, Including Discontinued Operation, Accounts Payable				133		133		150
Disposal group, including discontinued operations, accrued interest				20		20		15
Disposal Group, Including Discontinued Operation, Accrued Liabilities				151		151		150
Non Recourse Debt Held For Sale Or Discontinued Operations				373		373		346
Disposal Group, Including Discontinued Operation, Other Liabilities				164		164		110
Disposal Group, Including Discontinued Operation, Liabilities	[2]			841		841		784
Sul Subsidiary [Member] | Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Assets				1,048		1,048		1,210
Disposal Group, Including Discontinued Operation, Liabilities				841		841		771
Sul Subsidiary [Member] | Disposal Group, Held-for-sale, Not Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Assets	[3]			0		0		96
Disposal Group, Including Discontinued Operation, Liabilities	[3]			0		0		$ 13
Armenia Mountain [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Noncontrolling Interest, Ownership Percentage by Parent									100.00%
Pre-tax income of disposed businesses, Excluding gain on disposal, included in continuing operations				$ 2		6
Sul Subsidiary [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Discontinued Operation, Tax (Expense) Benefit from Provision for (Gain) Loss on Disposal						$ 135

[1] (3) Pre-tax impairment expense of $783 million is net of the impact from cumulative translation adjustments.

[2] (1) Amounts at December 31, 2015 are classified as both current and long-term on the Condensed Consolidated Balance Sheet.

[3] (2) DPLER and Kelanitissa classified as held-for-sale at December 31, 2015. See Note 16—Dispositions for further information.