Fair Value (Nonrecurring Measurements) (Details) - USD ($)		1 Months Ended	3 Months Ended							12 Months Ended
		Jun. 30, 2016	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017		Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017		Dec. 31, 2016
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Other Asset Impairment Charges			$ 42,000,000	$ 74,000,000	$ 92,000,000	$ 277,000,000		$ 90,000,000	$ 168,000,000	$ 208,000,000	$ 537,000,000		$ 1,096,000,000
Other non-operating expense										147,000,000	0		2,000,000
Discontinued Operation, Gain (Loss) from Disposal of Discontinued Operation, before Income Tax											(611,000,000)		$ (1,385,000,000)
Shady Point [Member]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring			30,000,000							30,000,000
Nejapa [Member]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring			5,000,000							5,000,000
Sul Subsidiary [Member]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring		$ 1,600,000,000
Estimate of Fair Value Measurement [Member] | Level 3
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring			214,000,000							214,000,000
Long Lived Assets Held And Used [Member]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Other Asset Impairment Charges	[1]										18,000,000
Long Lived Assets Held And Used [Member] | DPL Peaking Generation [Domain]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring		5,000,000				2,000,000					2,000,000
Long Lived Assets Held And Used [Member] | Laurel Mountain [Member]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Other Asset Impairment Charges	[1]										121,000,000
Assets Carrying Amount Disclosure Nonrecurring			33,000,000							33,000,000
Long Lived Assets Held And Used [Member] | Kilroot [Member]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Other Asset Impairment Charges	[1]										37,000,000
Assets Carrying Amount Disclosure Nonrecurring			20,000,000							20,000,000
Long Lived Assets Held And Used [Member] | DPL Subsidiary
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Other Asset Impairment Charges	[1]										66,000,000
Long Lived Assets Held And Used [Member] | Buffalo Gap [Member]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring						36,000,000					36,000,000
Long Lived Assets Held And Used [Member] | buffalo gap II [Member] [Member]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring						92,000,000					92,000,000
Long Lived Assets Held And Used [Member] | Estimate of Fair Value Measurement [Member] | Level 1
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1]					0					0
Long Lived Assets Held And Used [Member] | Estimate of Fair Value Measurement [Member] | Level 2
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1]					0					0
Long Lived Assets Held And Used [Member] | Estimate of Fair Value Measurement [Member] | Level 3
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1]					0					0
Long Lived Assets Held And Used [Member] | Estimate of Fair Value Measurement [Member] | Laurel Mountain [Member] | Level 1
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1]					0					0
Long Lived Assets Held And Used [Member] | Estimate of Fair Value Measurement [Member] | Laurel Mountain [Member] | Level 2
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1]					0					0
Long Lived Assets Held And Used [Member] | Estimate of Fair Value Measurement [Member] | Laurel Mountain [Member] | Level 3
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1]					33,000,000					33,000,000
Long Lived Assets Held And Used [Member] | Estimate of Fair Value Measurement [Member] | Kilroot [Member] | Level 1
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1]					0					0
Long Lived Assets Held And Used [Member] | Estimate of Fair Value Measurement [Member] | Kilroot [Member] | Level 2
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1]					0					0
Long Lived Assets Held And Used [Member] | Estimate of Fair Value Measurement [Member] | Kilroot [Member] | Level 3
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1]					20,000,000					20,000,000
Long Lived Assets Held And Used [Member] | Estimate of Fair Value Measurement [Member] | DPL Subsidiary | Level 1
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1]					0					0
Long Lived Assets Held And Used [Member] | Estimate of Fair Value Measurement [Member] | DPL Subsidiary | Level 2
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1]					0					0
Long Lived Assets Held And Used [Member] | Estimate of Fair Value Measurement [Member] | DPL Subsidiary | Level 3
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring			5,000,000			11,000,000	[1]			5,000,000	11,000,000	[1]
Long Lived Assets Held And Used [Member] | Reported Value Measurement [Member]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1],[2]					18,000,000					18,000,000
Long Lived Assets Held And Used [Member] | Reported Value Measurement [Member] | Laurel Mountain [Member]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1],[2]					154,000,000					154,000,000
Long Lived Assets Held And Used [Member] | Reported Value Measurement [Member] | Kilroot [Member]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1],[2]					69,000,000					69,000,000
Long Lived Assets Held And Used [Member] | Reported Value Measurement [Member] | DPL Subsidiary
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1],[2]					$ 77,000,000					$ 77,000,000
Long Lived Assets Held For Sale [Member] | Shady Point [Member]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Other Asset Impairment Charges	[1]									157,000,000
Long Lived Assets Held For Sale [Member] | Nejapa [Member]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Other Asset Impairment Charges	[1]									37,000,000
Long Lived Assets Held For Sale [Member] | guacolda [Member] | Level 3
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring			209,000,000							209,000,000
Long Lived Assets Held For Sale [Member] | Elsta [Member]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Other Asset Impairment Charges	[1]									3,000,000
Long Lived Assets Held For Sale [Member] | DPL Peaking Generation [Domain]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Other Asset Impairment Charges	[1]									109,000,000
Long Lived Assets Held For Sale [Member] | Kazakhstan [Member]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Other Asset Impairment Charges	[1]									94,000,000
Long Lived Assets Held For Sale [Member] | Kazakhstan Hydro [Member]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Other Asset Impairment Charges	[1],[3]									92,000,000
Long Lived Assets Held For Sale [Member] | Estimate of Fair Value Measurement [Member] | Shady Point [Member] | Level 1
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1]		0							0
Long Lived Assets Held For Sale [Member] | Estimate of Fair Value Measurement [Member] | Shady Point [Member] | Level 2
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1]		0							0
Long Lived Assets Held For Sale [Member] | Estimate of Fair Value Measurement [Member] | Shady Point [Member] | Level 3
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1]		30,000,000							30,000,000
Long Lived Assets Held For Sale [Member] | Estimate of Fair Value Measurement [Member] | Nejapa [Member] | Level 1
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1]		0							0
Long Lived Assets Held For Sale [Member] | Estimate of Fair Value Measurement [Member] | Nejapa [Member] | Level 2
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1]		0							0
Long Lived Assets Held For Sale [Member] | Estimate of Fair Value Measurement [Member] | Nejapa [Member] | Level 3
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1]		5,000,000							5,000,000
Long Lived Assets Held For Sale [Member] | Estimate of Fair Value Measurement [Member] | guacolda [Member] | Level 1
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1]		0							0
Long Lived Assets Held For Sale [Member] | Estimate of Fair Value Measurement [Member] | guacolda [Member] | Level 2
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1]		0							0
Long Lived Assets Held For Sale [Member] | Estimate of Fair Value Measurement [Member] | Elsta [Member] | Level 1
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1]		0							0
Long Lived Assets Held For Sale [Member] | Estimate of Fair Value Measurement [Member] | Elsta [Member] | Level 2
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1]		16,000,000							16,000,000
Long Lived Assets Held For Sale [Member] | Estimate of Fair Value Measurement [Member] | Elsta [Member] | Level 3
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1]		0							0
Long Lived Assets Held For Sale [Member] | Estimate of Fair Value Measurement [Member] | DPL Peaking Generation [Domain] | Level 1
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1]		0							0
Long Lived Assets Held For Sale [Member] | Estimate of Fair Value Measurement [Member] | DPL Peaking Generation [Domain] | Level 2
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1]		237,000,000							237,000,000
Long Lived Assets Held For Sale [Member] | Estimate of Fair Value Measurement [Member] | DPL Peaking Generation [Domain] | Level 3
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1]		0							0
Long Lived Assets Held For Sale [Member] | Estimate of Fair Value Measurement [Member] | Kazakhstan [Member] | Level 1
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1]		0							0
Long Lived Assets Held For Sale [Member] | Estimate of Fair Value Measurement [Member] | Kazakhstan [Member] | Level 2
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1]		29,000,000							29,000,000
Long Lived Assets Held For Sale [Member] | Estimate of Fair Value Measurement [Member] | Kazakhstan [Member] | Level 3
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1]		0							0
Long Lived Assets Held For Sale [Member] | Estimate of Fair Value Measurement [Member] | Kazakhstan Hydro [Member] | Level 1
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1]		0							0
Long Lived Assets Held For Sale [Member] | Estimate of Fair Value Measurement [Member] | Kazakhstan Hydro [Member] | Level 2
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1]		92,000,000							92,000,000
Long Lived Assets Held For Sale [Member] | Estimate of Fair Value Measurement [Member] | Kazakhstan Hydro [Member] | Level 3
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1]		0							0
Long Lived Assets Held For Sale [Member] | Reported Value Measurement [Member] | Shady Point [Member]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1],[2]		211,000,000							211,000,000
Long Lived Assets Held For Sale [Member] | Reported Value Measurement [Member] | Nejapa [Member]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1],[2]		42,000,000							42,000,000
Long Lived Assets Held For Sale [Member] | Reported Value Measurement [Member] | guacolda [Member]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1],[2]		354,000,000							354,000,000
Long Lived Assets Held For Sale [Member] | Reported Value Measurement [Member] | Elsta [Member]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1],[2]		19,000,000							19,000,000
Long Lived Assets Held For Sale [Member] | Reported Value Measurement [Member] | DPL Peaking Generation [Domain]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1],[2]		346,000,000							346,000,000
Long Lived Assets Held For Sale [Member] | Reported Value Measurement [Member] | Kazakhstan [Member]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1],[2]		171,000,000							171,000,000
Long Lived Assets Held For Sale [Member] | Reported Value Measurement [Member] | Kazakhstan Hydro [Member]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1],[2]		$ 190,000,000							$ 190,000,000
Discontinued Operations, Held-for-sale [Member] | Sul Subsidiary [Member]
Fair Value Assets Measured On Nonrecurring Basis Unobservable Inputs [Line Items]
Other Asset Impairment Charges		$ 783,000,000

[1] See Note 20—Asset Impairment Expense for further information.

[2] Represents the carrying values at the dates of initial measurement, before fair value adjustment.

[3] Per the Company's policy, pre-tax loss is limited to the impairment of long-lived assets. Any additional loss will be recognized on completion of the sale. Upon disposal of Kazakhstan HPPs, the Company incurred an additional pre-tax loss on disposal of $33 million. See Note 20—Asset Impairment Expense and Note 23—Held-for-Sale and Dispositions for further information