Derivative Instruments and Hedging Activities (Outstanding Derivative Instruments) (Details) - Designated as Hedging Instrument [Member] - Interest Rate Swap [Member] $ in Millions	Sep. 30, 2020 USD ($)
Derivative, Notional Amount, Purchase (Sales), Net	$ 140.0
Subsidiaries [Member]
Derivative, Notional Amount, Purchase (Sales), Net	$ 140.0

Derivative, Notional Amount, Purchase (Sales), Net

No definition available.

Name:	dpl_DerivativeNotionalAmountPurchaseSalesNet
Namespace Prefix:	dpl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant