Debt Covenant, Debt to EBITDA Ratio, Maximum

No definition available.

Name:	dpl_DebtCovenantDebttoEBITDARatioMaximum
Namespace Prefix:	dpl_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt Covenant, Interest Coverage Ratio, Minimum

+ References

No definition available.

+ Details

Name:	dpl_DebtCovenantInterestCoverageRatioMinimum
Namespace Prefix:	dpl_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt Covenant, Leverage Ratio, Maximum

+ References

No definition available.

+ Details

Name:	dpl_DebtCovenantLeverageRatioMaximum
Namespace Prefix:	dpl_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt Covenant, Total Debt to Total Capitalization Ratio, Maximum

+ References

No definition available.

+ Details

Name:	dpl_DebtCovenantTotalDebttoTotalCapitalizationRatioMaximum
Namespace Prefix:	dpl_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt Instrument, Debt Covenant, Debt to EBITDA Ratio, Number of Quarters

+ References

No definition available.

+ Details

Name:	dpl_DebtInstrumentDebtCovenantDebttoEBITDARatioNumberofQuarters
Namespace Prefix:	dpl_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Debt Instrument, Debt Covenant, EBITDA to Interest Calculation, Number of Quarters

+ References

No definition available.

+ Details

Name:	dpl_DebtInstrumentDebtCovenantEBITDAtoInterestCalculationNumberofQuarters
Namespace Prefix:	dpl_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Debt Instrument, Number of Financial Covenants

+ References

No definition available.

+ Details

Name:	dpl_DebtInstrumentNumberofFinancialCovenants
Namespace Prefix:	dpl_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Debt to EBITDA Ratio

+ References

No definition available.

+ Details

Name:	dpl_DebttoEBITDARatio
Namespace Prefix:	dpl_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Early prepayment rate - prepayments prior to July 3, 2018 must be at this rate

+ References

No definition available.

+ Details

Name:	dpl_Earlyprepaymentrate
Namespace Prefix:	dpl_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Interest Coverage Ratio

+ References

No definition available.

+ Details

Name:	dpl_InterestCoverageRatio
Namespace Prefix:	dpl_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Leverage Ratio

+ References

No definition available.

+ Details

Name:	dpl_LeverageRatio
Namespace Prefix:	dpl_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

After separation required compliance with the financial covenant, shall be suspended from 1/1/17 to 12/31/17 if during such time DP&L's LT indebtedness (as determined by the PUCO) is less than or equal to $750.0 million.

+ References

No definition available.

+ Details

Name:	dpl_LongTermIndebtednessLessthanorEqualto
Namespace Prefix:	dpl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Make Whole Premium

+ References

No definition available.

+ Details

Name:	dpl_MakeWholePremium
Namespace Prefix:	dpl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Standard Repayment Rate - Repayment rate after July 31, 2018

+ References

No definition available.

+ Details

Name:	dpl_StandardRepaymentRate
Namespace Prefix:	dpl_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Total Long-term Debt At Subsidiary With Purchase Accounting Adjustments

+ References

No definition available.

+ Details

Name:	dpl_TotalLongtermDebtAtSubsidiaryWithPurchaseAccountingAdjustments
Namespace Prefix:	dpl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Unamortized adjustments to market value from purchase accounting

+ References

No definition available.

+ Details

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

- Definition

Unamortized Deferred Financing Costs

+ References

No definition available.

+ Details

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

- Definition

Unamortized Deferred Financing Costs (Subsidiary)

+ References

No definition available.

+ Details

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

- Definition

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031897-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

Name:	us-gaap_DebtInstrumentCarryingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Latest date the outstanding debt instruments are required to be repaid, in CCYY-MM-DD format.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(2))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentMaturityDateRangeEnd1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, after accumulated amortization, of debt discount (premium).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28555-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28567-108399

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28541-108399

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

Name:	us-gaap_DebtInstrumentUnamortizedDiscountPremiumNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Gross amount of debt extinguished.

+ References

No definition available.

+ Details

Name:	us-gaap_ExtinguishmentOfDebtAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of long-term debt and capital lease obligations including current maturities.

+ References

No definition available.

+ Details

Name:	us-gaap_LongTermDebtAndCapitalLeaseObligationsIncludingCurrentMaturities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19,20)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_LongTermDebtCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-04.(a))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24072-122690

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601

+ Details

Name:	us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

+ Details

Name:	us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_LongTermDebtNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	srt_ConsolidatedEntitiesAxis=srt_SubsidiariesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=dpl_SeniorUnsecuredNotesAt6.80MaturingOnOctober2019Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=dpl_TermLoanMaturing2022DPLMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=dpl_EurodollarrateTermLoanBMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=dpl_BaseRateTermLoanBMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=dpl_RevolvingCreditAgreementandStandbyLettersofCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=dpl_FourPointTwoZeroPercentageOfUSGovernmentNoteMaturingInFebruaryTwoThousandSixtyOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=dpl_TermLoanMaturing2022Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=dpl_BankTermLoanMaturingInMay2018Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=dpl_BankTermLoanMaturingJuly2020Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=dpl_FiveYearSeniorUnsecuredNotesAt6.75MaturingOctober152019Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=dpl_DPLRevolvingCreditAgreementandTermLoanMaturingJuly2020Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=dpl_TenYearSeniorUnsecuredNotesAt725MaturingAtOctober152021Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=dpl_EightPointOneTwoFivePercentageOfNoteToCapitalTrustIiMaturingInSeptemberTwoThousandThirtyOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=dpl_VariableRateNotesBackedbyTermLoanandFirstMortgageBondsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=dpl_OnePointOneThreeToOnePointOneSevenBondsMaturingInAugustTwoThousandTwentyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByAssetClassAxis=us-gaap_DebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Debt (Narrative) (Details) $ in Millions	6 Months Ended				9 Months Ended	12 Months Ended
Debt (Narrative) (Details) $ in Millions	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018 USD ($) debt_covenant fiscal_quarter	Jul. 03, 2018	Sep. 30, 2018 debt_covenant	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018 USD ($) debt_covenant fiscal_quarter	Dec. 31, 2017 USD ($)	Apr. 30, 2018 USD ($)	Mar. 30, 2018 USD ($)	Jan. 03, 2018	Aug. 03, 2015 USD ($)
Debt Instrument [Line Items]
Current portion - long-term debt			$ 103.6					$ 103.6
Unamortized adjustments to market value from purchase accounting			1.9					1.9
Unamortized Deferred Financing Costs			(4.3)					(4.3)	$ (6.8)
Current portion - long-term debt			103.6					$ 103.6	4.6
Debt Covenant, Leverage Ratio, Maximum								0.67
Debt Covenant, Interest Coverage Ratio, Minimum					2.50			2.10
Interest Coverage Ratio								2.61
Leverage Ratio								1.47
Debt Covenant, Total Debt to Total Capitalization Ratio, Maximum								0.65
Long Term Indebtedness, Less than or Equal to								$ 750.0	750.0
Debt Instrument, Unamortized Discount (Premium), Net			0.5					0.5	0.6
Total Long-term Debt At Subsidiary With Purchase Accounting Adjustments			586.1					586.1	646.6
Long-term Debt, Excluding Current Maturities			1,372.3					1,372.3	1,700.2
Long-term Debt, Maturities, Repayments of Principal in Year Two			144.7					$ 144.7
Debt Covenant, Debt to EBITDA Ratio, Maximum								7.25
Debt to EBITDA Ratio								5.84
THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument [Line Items]
Current portion - long-term debt			4.6					$ 4.6
Unamortized Deferred Financing Costs									(9.8)
Current portion - long-term debt			4.6					$ 4.6	4.6
Debt Covenant, Interest Coverage Ratio, Minimum								2.50
Debt Covenant, Total Debt to Total Capitalization Ratio, Maximum								0.65
Long Term Indebtedness, Less than or Equal to								$ 750.0	750.0
Unamortized Deferred Financing Costs (Subsidiary)			(6.3)					(6.3)	(9.8)
Debt Instrument, Unamortized Discount (Premium), Net			1.4					1.4	2.0
Long-term Debt, Excluding Current Maturities			581.5					581.5	642.0
Long-term Debt, Maturities, Repayments of Principal in Year Two			$ 144.7					144.7
Senior Unsecured Notes At6.80 Maturing On October2019 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross											$ 200.0
Make Whole Premium										$ 5.1
Extinguishment of debt, amount								$ 101.0
Debt instrument interest percentage			6.75%					6.75%
Term Loan Maturing 2022 (DPL) [Member]
Debt Instrument [Line Items]
Debt Instrument, Maturity Date Range, End								Aug. 24, 2022
Long-term Debt, Gross			$ 436.1					$ 436.1	440.6
Term Loan Maturing 2022 (DPL) [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument [Line Items]
Debt Instrument, Maturity Date Range, End								Aug. 24, 2022
Long-term Debt, Gross			$ 436.1					$ 436.1	440.6
Eurodollar rate Term Loan B [Member]
Debt Instrument [Line Items]
Debt instrument interest percentage			3.25%					3.25%				2.00%
Eurodollar rate Term Loan B [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument [Line Items]
Debt instrument interest percentage			3.25%					3.25%				2.00%
Base Rate Term Loan B [Member]
Debt Instrument [Line Items]
Debt instrument interest percentage			2.25%					2.25%				1.00%
Base Rate Term Loan B [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument [Line Items]
Debt instrument interest percentage			2.25%					2.25%				1.00%
Revolving Credit Agreement and Standby Letters of Credit [Member]
Debt Instrument [Line Items]
Number of financial covenants \| debt_covenant					2
Revolving Credit Agreement and Standby Letters of Credit [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument [Line Items]
Number of financial covenants \| debt_covenant					2
Number of prior quarters included in debt to EBITDA ratio \| fiscal_quarter			4					4
Debt Covenant, Interest Coverage Ratio, Minimum								2.50
Interest Coverage Ratio								8.09
U.S. Government note maturing in 2061 - 4.20% [Member]
Debt Instrument [Line Items]
Debt Instrument, Maturity Date Range, End								Feb. 01, 2061
Long-term Debt, Gross			$ 17.7					$ 17.7	17.8
Debt instrument interest percentage			4.20%					4.20%
U.S. Government note maturing in 2061 - 4.20% [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument [Line Items]
Debt Instrument, Maturity Date Range, End								Feb. 01, 2061
Long-term Debt, Gross			$ 17.7					$ 17.7	17.8
Debt instrument interest percentage			4.20%					4.20%
Term Loan Maturing 2022 [Member]
Debt Instrument [Line Items]
Early prepayment rate				101.00%
Standard Repayment Rate			100.00%
Term Loan Maturing 2022 [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument [Line Items]
Early prepayment rate				101.00%
Standard Repayment Rate			100.00%
Bank Term Loan maturing in May 2018 [Member]
Debt Instrument [Line Items]
Debt Instrument, Maturity Date Range, End								Jul. 31, 2020
Bank Term Loan Maturing July 2020 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross			$ 0.0					$ 0.0	70.0
Extinguishment of debt, amount								$ 70.0
Five Year Senior Unsecured Notes At6.75 Maturing October152019 [Member]
Debt Instrument [Line Items]
Debt Instrument, Maturity Date Range, End								Oct. 01, 2019
Long-term Debt, Gross			$ 99.0					$ 99.0	200.0
Debt instrument interest percentage			6.75%					6.75%
DPL Revolving Credit Agreement and Term Loan Maturing July 2020 [Member]
Debt Instrument [Line Items]
Number of financial covenants \| debt_covenant			2					2
Debt Instrument, Debt Covenant, Debt to EBITDA Ratio, Number of Quarters \| fiscal_quarter			4					4
Senior Unsecured Bonds at 7.25% maturing in 2021 [Member]
Debt Instrument [Line Items]
Debt Instrument, Maturity Date Range, End								Oct. 01, 2021
Long-term Debt, Gross			$ 780.0					$ 780.0	780.0
Debt instrument interest percentage			7.25%					7.25%
Note to DPL Capital Trust II Maturing in 2031 - 8.125% [Member]
Debt Instrument [Line Items]
Debt Instrument, Maturity Date Range, End								Sep. 01, 2031
Long-term Debt, Gross			$ 15.6					$ 15.6	15.6
Debt instrument interest percentage			8.125%					8.125%
Variable Rate Notes Backed by Term Loan and First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Extinguishment of debt, amount								$ 60.0
Variable Rate Notes Backed by Term Loan and First Mortgage Bonds [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument [Line Items]
Extinguishment of debt, amount								$ 60.0
Debt Instrument, Face Amount													$ 200.0
One Point One Three To One Point One Seven Bonds Maturing In August Two Thousand Twenty [Member]
Debt Instrument [Line Items]
Debt Instrument, Maturity Date Range, End								Aug. 01, 2020
Long-term Debt, Gross			$ 140.0					$ 140.0	200.0
One Point One Three To One Point One Seven Bonds Maturing In August Two Thousand Twenty [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument [Line Items]
Debt Instrument, Maturity Date Range, End								Aug. 01, 2020
Long-term Debt, Gross			140.0					$ 140.0	200.0
Subsequent Event [Member]
Debt Instrument [Line Items]
Debt Covenant, Interest Coverage Ratio, Minimum							2.25
Debt Covenant, Debt to EBITDA Ratio, Maximum	6.75	7.00				6.50
Debt [Member]
Debt Instrument [Line Items]
Long-term Debt and Capital Lease Obligations, Including Current Maturities			1,475.9					1,475.9	1,704.8
Debt [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument [Line Items]
Long-term Debt and Capital Lease Obligations, Including Current Maturities			$ 586.1					$ 586.1	$ 646.6