Dispositions Dispositions (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Impairment of Long-Lived Assets Held-for-use	$ 0	$ 168
Proceeds from the sale of businesses, net of cash and restricted cash sold	1,180	4
Gain (Loss) on Disposition of Business	(788)	0
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	16	23
Disposal Group, Disposed of by 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	9	23
Proceeds from the sale of businesses, net of cash and restricted cash sold	1,050
Gain (Loss) on Disposition of Business	777
Tax on gain (loss) on disposition of business	155
Disposal Group, Disposed of by 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	7	0
Proceeds from the sale of businesses, net of cash and restricted cash sold	239
Gain (Loss) on Disposition of Business	(2)
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] | Beckjord Facility [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal	(12)
Asset Retirement Obligation, Cash Paid to Settle	(15)
Disposal Group, Not Discontinued Operations [Member] | Advancion Energy Storage [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain (Loss) on Disposition of Business	$ 23
Kazakhstan [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		$ 94