Regulatory Matters (Notes)	3 Months Ended
Regulatory Matters (Notes)	Mar. 31, 2020
Schedule of Regulatory Assets and Liabilities [Text Block]	Regulatory Matters DP&L ESP Orders Ohio law requires utilities to file either an ESP or MRO plan to establish SSO rates. From November 1, 2017 through December 18, 2019, DP&L operated pursuant to an approved ESP plan, which was initially filed on March 13, 2017 (ESP 3). On November 21, 2019, the PUCO issued a supplemental order modifying ESP 3, and as a result DP&L filed a Notice of Withdrawal of its ESP 3 Application and requested to revert to the ESP rates that were in effect prior to ESP 3. The Notice of Withdrawal was approved by the PUCO on December 18, 2019. The PUCO order required, among other things, DP&L to conduct both an ESP v. MRO Test to validate that the ESP is expected to be more favorable in the aggregate than what would be experienced under an MRO, and a prospective SEET, which were filed with the PUCO on April 1, 2020. A comment period is set for July 2020 and an evidentiary hearing regarding this matter is scheduled for October 2020 (if needed) with a final ruling expected in early 2021. DP&L is also subject to an annual retrospective SEET. The ultimate outcome of the ESP v. MRO and SEET proceedings could have a material adverse effect on DP&L’s results of operations, financial condition and cash flows. Certain parties which intervened in the ESP proceedings have filed petitions for rehearing of the recent PUCO ESP orders; some of which seek to eliminate DP&L’s RSC from the ESP 1 rates that are currently in place and others seek to re-implement the 2017 ESP, but without the DMR. We are unable to predict the outcomes of these petitions, but if these result in terms that are more adverse than DP&L's current ESP rate plan, it could have a material adverse effect on our results of operations, financial condition and cash flows. On January 23, 2020 DP&L filed with the PUCO requesting approval to defer its decoupling costs consistent with the methodology approved in its Distribution Rate Case. If approved, deferral would be effective December 18, 2019 and going forward would reduce impacts of weather, energy efficiency programs and economic changes in customer demand. In response to the PUCO’s COVID-19 emergency orders, DP&L filed an Application on March 23, 2020, requesting waivers of certain rule and tariff requirements and deferral of certain costs and revenues including those related to deposits and reconnection fees, late payment fees, credit card fees; and waived or uncollected amounts associated with putting customers on payment plans. On April 15, 2020, DP&L filed a Supplemental Application related to the COVID-19 emergency requesting certain tariff modifications for commercial and industrial customers, and deferral of the amounts associated with waiving minimum demand charges. See Note 14 – Risks and Uncertainties for additional information regarding the COVID-19 pandemic. FERC Proceedings On November 15, 2018 FERC issued a Notice of Proposed Rulemaking (NOPR) to address amortization of excess accumulated deferred income taxes resulting from the TCJA and their impact on transmission rates. Such notice requires all public utility transmission providers with stated transmission rates under an Open Access Transmission Tariff (OATT) to determine the amount of excess deferred income taxes caused by the TCJA. On March 3, 2020, DP&L filed an application before the FERC to change its transmission rate from a stated rate to a formula rate, which was accepted by the FERC and made effective as of May 3, 2020, subject to further proceeding and potential refunds. The formula rate includes adjustments to flow back over time the excess deferred income taxes caused by the TCJA. The NOPR, therefore, no longer applies to DP&L. The rate changes will increase revenues by approximately $4.1 million through the end of 2020, subject to refund based on final approved rates.
Subsidiaries [Member]
Schedule of Regulatory Assets and Liabilities [Text Block]	Regulatory Matters DP&L ESP Orders Ohio law requires utilities to file either an ESP or MRO plan to establish SSO rates. From November 1, 2017 through December 18, 2019, DP&L operated pursuant to an approved ESP plan, which was initially filed on March 13, 2017 (ESP 3). On November 21, 2019, the PUCO issued a supplemental order modifying ESP 3, and as a result DP&L filed a Notice of Withdrawal of its ESP 3 Application and requested to revert to the ESP rates that were in effect prior to ESP 3. The Notice of Withdrawal was approved by the PUCO on December 18, 2019. The PUCO order required, among other things, DP&L to conduct both an ESP v. MRO Test to validate that the ESP is expected to be more favorable in the aggregate than what would be experienced under an MRO, and a prospective SEET, which were filed with the PUCO on April 1, 2020. A comment period is set for July 2020 and an evidentiary hearing regarding this matter is scheduled for October 2020 (if needed) with a final ruling expected in early 2021. DP&L is also subject to an annual retrospective SEET. The ultimate outcome of the ESP v. MRO and SEET proceedings could have a material adverse effect on DP&L’s results of operations, financial condition and cash flows. Certain parties which intervened in the ESP proceedings have filed petitions for rehearing of the recent PUCO ESP orders; some of which seek to eliminate DP&L’s RSC from the ESP 1 rates that are currently in place and others seek to re-implement the 2017 ESP, but without the DMR. We are unable to predict the outcomes of these petitions, but if these result in terms that are more adverse than DP&L's current ESP rate plan, it could have a material adverse effect on our results of operations, financial condition and cash flows. On January 23, 2020 DP&L filed with the PUCO requesting approval to defer its decoupling costs consistent with the methodology approved in its Distribution Rate Case. If approved, deferral would be effective December 18, 2019 and going forward would reduce impacts of weather, energy efficiency programs and economic changes in customer demand. In response to the PUCO’s COVID-19 emergency orders, DP&L filed an Application on March 23, 2020, requesting waivers of certain rule and tariff requirements and deferral of certain costs and revenues including those related to deposits and reconnection fees, late payment fees, credit card fees; and waived or uncollected amounts associated with putting customers on payment plans. On April 15, 2020, DP&L filed a Supplemental Application related to the COVID-19 emergency requesting certain tariff modifications for commercial and industrial customers, and deferral of the amounts associated with waiving minimum demand charges. See Note 11 – Risks and Uncertainties for additional information regarding the COVID-19 pandemic. FERC Proceedings On November 15, 2018 FERC issued a Notice of Proposed Rulemaking (NOPR) to address amortization of excess accumulated deferred income taxes resulting from the TCJA and their impact on transmission rates. Such notice requires all public utility transmission providers with stated transmission rates under an Open Access Transmission Tariff (OATT) to determine the amount of excess deferred income taxes caused by the TCJA. On March 3, 2020, DP&L filed an application before the FERC to change its transmission rate from a stated rate to a formula rate, which was accepted by the FERC and made effective as of May 3, 2020, subject to further proceeding and potential refunds. The formula rate includes adjustments to flow back over time the excess deferred income taxes caused by the TCJA. The NOPR, therefore, no longer applies to DP&L. The rate changes will increase revenues by approximately $4.1 million through the end of 2020, subject to refund based on final approved rates.