Acquisitions and Dispositions (Details) - USD ($)		3 Months Ended			9 Months Ended	12 Months Ended
	May 22, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019		Dec. 31, 2018	Mar. 20, 2018	Dec. 31, 2017
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Gain (Loss) on Disposition of Business						$ (95,000,000)	$ 28,000,000		$ 984,000,000
Proceeds from Divestiture of Businesses and Interests in Affiliates						169,000,000	178,000,000		2,020,000,000
Income (Loss) from Continuing Operations Attributable to Parent						(43,000,000)	(302,000,000)		(985,000,000)
Dispositions and Held-for-Sales Businesses
Asset Retirement Obligation, Revision of Estimate						$ 3,000,000	58,000,000
JORDAN
Dispositions and Held-for-Sales Businesses
Equity Method Investment, Ownership Percentage						10.00%
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						$ 121,000,000	94,000,000		109,000,000
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Mong Duong Subsidiary [Member]
Dispositions and Held-for-Sales Businesses
Disposal Group Not Discontinued Operation Ownership Interest Sold						51.00%
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Mong Duong Finance Holdings B.V._Related Party [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						$ 55,000,000	34,000,000		48,000,000
Dispositions and Held-for-Sales Businesses
Disposal Group Not Discontinued Operation Ownership Interest Sold						51.00%
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Itabo Disposal Group
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						$ 41,000,000	30,000,000		33,000,000
Proceeds from Divestiture of Businesses					$ 101,000,000	$ 92,000,000
Dispositions and Held-for-Sales Businesses
Disposal Group Not Discontinued Operation Ownership Interest Sold						43.00%
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Estrella del Mar I
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						$ 5,000,000	12,000,000		17,000,000
Assets Carrying Amount Disclosure Nonrecurring						16,000,000
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Itabo Opco [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Assets Carrying Amount Disclosure Nonrecurring						189,000,000
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Mong Duong held-dfor-sale [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Assets Carrying Amount Disclosure Nonrecurring						472,000,000
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | JORDAN
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						20,000,000	$ 18,000,000		11,000,000
Assets Carrying Amount Disclosure Nonrecurring						154,000,000
Proceeds from Divestiture of Businesses						$ 58,000,000
Dispositions and Held-for-Sales Businesses
Disposal Group Not Discontinued Operation Ownership Interest Sold						26.00%	36.00%
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							$ 44,000,000		154,000,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] | Kilroot and Ballylumford [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							(1,000,000)		35,000,000
Gain (Loss) on Disposition of Business							33,000,000
Proceeds from Divestiture of Businesses and Interests in Affiliates							118,000,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] | DPL 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							52,000,000	[1],[2]	77,000,000
Asset Retirement Obligation, Cash Paid to Settle						$ 51,000,000
Dispositions and Held-for-Sales Businesses
Pre-tax gain on disposal						20,000,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] | Shady Point [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							(5,000,000)		19,000,000
Proceeds from Divestiture of Businesses and Interests in Affiliates	$ 29,000,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] | Redondo Beach [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Assets Carrying Amount Disclosure Nonrecurring						24,000,000
Dispositions and Held-for-Sales Businesses
Gain (Loss) on Disposition of Assets						41,000,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] | Compania Transmisora del Norte Grande [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Gain (Loss) on Disposition of Business							126,000,000
Proceeds from Divestiture of Businesses and Interests in Affiliates							225,000,000
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]
Asset Retirement Obligation, Cash Paid to Settle		$ 15,000,000
Dispositions and Held-for-Sales Businesses
Pre-tax gain on disposal		(12,000,000)
Disposal Group, Disposed of by 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]
Gain (Loss) on Disposition of Business			$ 70,000,000
Proceeds from Divestiture of Businesses and Interests in Affiliates			$ 287,000,000
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]
Gain (Loss) on Disposition of Business		(2,000,000)
Proceeds from Divestiture of Businesses and Interests in Affiliates		239,000,000
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							0		9,000,000
Gain (Loss) on Disposition of Business									772,000,000
Proceeds from Divestiture of Businesses and Interests in Affiliates				$ 1,050,000,000.00
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]
Proceeds from Divestiture of Businesses and Interests in Affiliates									75,000,000
Dispositions and Held-for-Sales Businesses
Pre-tax gain on disposal						(30,000,000)
Proceeds from Legal Settlements						45,000,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] | Other Subsidiaries [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							(2,000,000)		14,000,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] | Uruguaiana [Member]
Dispositions and Held-for-Sales Businesses
Pre-tax gain on disposal						(90,000,000)
Guaranty Liabilities						$ 22,000,000
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		$ 23,000,000
Masinloc Subsidiary [Member]
Dispositions and Held-for-Sales Businesses
Disposal Group Not Discontinued Operation Ownership Interest Sold										51.00%
Kazakhstan Hydro [Member] | Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member]
Dispositions and Held-for-Sales Businesses
Disposal Group Not Discontinued Operation Ownership Interest Sold											100.00%
DPL Subsidiary [Member]
Dispositions and Held-for-Sales Businesses
Asset Retirement Obligation, Revision of Estimate							$ 87,000,000		$ 32,000,000

[1] After the retirement of Stuart and Killen in 2018, the Company entered into contracts to buy back all open capacity years for the plants at prices lower than the PJM capacity revenue prices. As such, the Company continued to earn capacity margin until the plants were transferred in December 2019.

[2] Reductions in the asset retirement obligations for ash ponds and landfills at Stuart and Killen in 2018 resulted in a $32 million reduction to cost of sales. See Note 4—Asset Retirement Obligations for further information.