Acquisitions and Dispositions (Details) - USD ($) $ in Millions						3 Months Ended		12 Months Ended
	Apr. 07, 2017	Jan. 27, 2016	Jan. 01, 2016	Mar. 31, 2015	Jun. 25, 2014	Jun. 30, 2016	Sep. 30, 2015	Dec. 31, 2017	Dec. 31, 2016	Sep. 16, 2016	Dec. 31, 2015	Dec. 17, 2017	Jun. 30, 2017
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Gain (Loss) on Disposition of Business								$ (52)	$ 29		$ 29
Proceeds from Divestiture of Businesses and Interests in Affiliates								108	631		138
Income (Loss) from Continuing Operations Attributable to Parent								(507)	(20)		318
Dispositions and Held-for-Sales Businesses
Proceeds from Sale of Ownership Interests								94	0		154
Masinloc Subsidiary [Member]
Dispositions and Held-for-Sales Businesses
Sale of Stock, Consideration Received on Transaction					$ 436
Disposal Group, Held-for-sale, Not Discontinued Operations [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Income (Loss) from Individually Significant Component Disposed of or Held-for-sale, Excluding Discontinued Operations, Attributable to Parent, before Income Tax								129	134		133
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Electrica Santiago (Gener ESSA) [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Income (Loss) from Individually Significant Component Disposed of or Held-for-sale, Excluding Discontinued Operations, Attributable to Parent, before Income Tax								9	11		10
Proceeds from Divestiture of Businesses and Interests in Affiliates								300
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | DPL Peaking Generation [Domain]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Income (Loss) from Individually Significant Component Disposed of or Held-for-sale, Excluding Discontinued Operations, Attributable to Parent, before Income Tax								17	20		24
Proceeds from Divestiture of Businesses and Interests in Affiliates								241
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Masinloc Subsidiary [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Income (Loss) from Individually Significant Component Disposed of or Held-for-sale, Excluding Discontinued Operations, Attributable to Parent, before Income Tax								103	103		99
Proceeds from Divestiture of Businesses and Interests in Affiliates								1,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Income (Loss) from Individually Significant Component Disposed of or Held-for-sale, Excluding Discontinued Operations, Attributable to Parent, before Income Tax								72	32		91
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] | Zimmer and Miami Fort [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Income (Loss) from Individually Significant Component Disposed of or Held-for-sale, Excluding Discontinued Operations, Attributable to Parent, before Income Tax								26	(14)		6
Gain (Loss) on Disposition of Business								13
Proceeds from Divestiture of Businesses and Interests in Affiliates								70
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] | Kazakhstan Hydro [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Income (Loss) from Individually Significant Component Disposed of or Held-for-sale, Excluding Discontinued Operations, Attributable to Parent, before Income Tax								33	34		52
Gain (Loss) on Disposition of Business								(33)
Proceeds from Divestiture of Businesses and Interests in Affiliates								75
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] | Armenia Mountain [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Income (Loss) from Individually Significant Component Disposed of or Held-for-sale, Excluding Discontinued Operations, Attributable to Parent, before Income Tax								0	0		6
Gain (Loss) on Disposition of Business							$ 22
Proceeds from Divestiture of Businesses and Interests in Affiliates							$ 64
Dispositions and Held-for-Sales Businesses
Ownership interest sold				100.00%
Sale Agreement, Buyer Option To Purchase Ownership Interest, Sales Price				$ 75
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] | UK Wind Projects
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Gain (Loss) on Disposition of Business						$ (20)
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] | Kelanitissa [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Gain (Loss) on Disposition of Business		$ 5
Proceeds from Divestiture of Businesses and Interests in Affiliates		$ 18
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] | Kazakhstan [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Income (Loss) from Individually Significant Component Disposed of or Held-for-sale, Excluding Discontinued Operations, Attributable to Parent, before Income Tax								13	12		16
Gain (Loss) on Disposition of Business	$ (49)
Proceeds from Divestiture of Businesses and Interests in Affiliates	$ 24
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] | DPLER [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Income (Loss) from Individually Significant Component Disposed of or Held-for-sale, Excluding Discontinued Operations, Attributable to Parent, before Income Tax								$ 0	0		11
Gain (Loss) on Disposition of Business			$ 49
Proceeds from Divestiture of Businesses and Interests in Affiliates			$ 76
Masinloc Subsidiary [Member]
Dispositions and Held-for-Sales Businesses
Ownership interest sold					45.00%			100.00%				51.00%
Divestiture of Businesses, Portion Contingent Upon Achievement of Certain Restructuring Efficiencies					$ 23
Kazakhstan Hydro [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Impairment of Long-Lived Assets to be Disposed of								$ 92	0		$ 0
Distributed energy [Domain]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Business Combination, Consideration Transferred										$ 43
UK Wind Projects
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Gain (Loss) on Disposition of Business									$ (20)
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Masinloc Subsidiary [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Assets Carrying Amount Disclosure Nonrecurring								475
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | DPL Peaking Generation [Domain]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Impairment of Long-Lived Assets to be Disposed of								109
Fair Value Less Costs To Sell								237
Assets Carrying Amount Disclosure Nonrecurring								346
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Electrica Santiago (Gener ESSA) [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Assets Carrying Amount Disclosure Nonrecurring								186
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Kazakhstan Hydro [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Impairment of Long-Lived Assets to be Disposed of								$ 92
Fair Value Less Costs To Sell													$ 92
Assets Carrying Amount Disclosure Nonrecurring													$ 190