Derivative Instruments and Hedging Activities (Outstanding Derivative Instruments) (Details) - Designated as Hedging Instrument [Member] - Interest Rate Swap [Member]	Dec. 31, 2019 USD ($)
Derivative, Notional Amount, Purchase (Sales), Net	$ 140,000,000.0
THE DAYTON POWER AND LIGHT COMPANY [Member]
Derivative, Notional Amount, Purchase (Sales), Net	$ 140,000,000.0

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