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

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

+ 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

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

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the 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))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: 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

Reference 3: 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

+ Details

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

- Definition

The cash inflow from a debt initially having maturity due after one year or beyond the operating cycle, if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3255-108585

+ Details

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

- Definition

The cash outflow for debt initially having maturity due after one year or beyond the normal operating cycle, if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3291-108585

+ Details

Name:	us-gaap_RepaymentsOfLongTermDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- 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_VariableRateNotesBackedbyTermLoanandFirstMortgageBondsMember
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_TermLoanMaturing2022Member
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_DPLRevolvingCreditAgreementandTermLoanMaturingJuly2020Member
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_EurodollarrateTermLoanBMember
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_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementScenarioAxis=us-gaap_ScenarioForecastMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=dpl_TenYearSeniorUnsecuredBondsAt435MaturingAtApril152029Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Debt (Narrative) (Details) $ in Millions				3 Months Ended		6 Months Ended			12 Months Ended
Debt (Narrative) (Details) $ in Millions	May 07, 2019 USD ($)	Apr. 17, 2019 USD ($)	Apr. 04, 2019 USD ($)	Mar. 31, 2019 USD ($) debt_covenant fiscal_quarter	Mar. 31, 2018 USD ($)	Dec. 31, 2019	Jun. 30, 2019	Jul. 03, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Apr. 30, 2018 USD ($)	Mar. 30, 2018 USD ($)	Jan. 03, 2018	Aug. 03, 2015 USD ($)
Debt Instrument [Line Items]
Long-term Line of Credit				$ 0.0							$ 0.0
Retirement of long-term debt				$ 1.1	$ 131.1
Debt Covenant, Debt to EBITDA Ratio, Maximum											7.25
Debt to EBITDA Ratio				5.83
Long Term Indebtedness, Less than or Equal to												$ 750.0
Debt Covenant, Leverage Ratio, Maximum				0.67
Debt Covenant, Interest Coverage Ratio, Minimum				2.50							2.10
Leverage Ratio				1.40
Debt Covenant, Total Debt to Total Capitalization Ratio, Maximum				0.65								0.75
Interest Coverage Ratio				2.73
THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument [Line Items]
Long-term Line of Credit				$ 0.0							$ 0.0
Retirement of long-term debt				$ 1.1	$ 61.1
Long Term Indebtedness, Less than or Equal to												$ 750.0
Debt Covenant, Interest Coverage Ratio, Minimum				2.50
Debt Covenant, Total Debt to Total Capitalization Ratio, Maximum				0.65								0.75
Senior unsecured due in October 2019 - 6.75% [Member]
Debt Instrument [Line Items]
Extinguishment of Debt, Amount				$ 101.0
Long-term Debt, Gross				$ 99.0							99.0			$ 200.0
Make Whole Premium													$ 5.1
Debt instrument interest percentage				6.75%
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
Long-term Debt, Gross				140.0							140.0
Debt Instrument, Face Amount																$ 200.0
Bank term loan due in July 2020 - rates from: 2.44% - 2.45% [Member]
Debt Instrument [Line Items]
Extinguishment of Debt, Amount				70.0
Term Loan Maturing 2022 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross				$ 435.0							436.1
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]
Long-term Debt, Gross				$ 435.0							$ 436.1
Early prepayment rate								101.00%
Standard Repayment Rate				100.00%
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 EBITDA to interest calculation \| fiscal_quarter				4
Debt Covenant, Interest Coverage Ratio, Minimum				2.50
Interest Coverage Ratio				8.99
DPL Revolving Credit Agreement and Term Loan Maturing July 2020 [Member]
Debt Instrument [Line Items]
Number of financial covenants \| debt_covenant				2
Number of prior quarters included in EBITDA to interest calculation \| fiscal_quarter				4
Number of prior quarters included in debt to EBITDA ratio \| fiscal_quarter				4
Base Rate Term Loan B [Member]
Debt Instrument [Line Items]
Debt instrument interest percentage											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%				1.00%
Eurodollar rate Term Loan B [Member]
Debt Instrument [Line Items]
Debt instrument interest percentage											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%				2.00%
Ten Year Senior Unsecured Notes At725 Maturing At October152021 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross				$ 780.0							$ 780.0
Debt instrument interest percentage				7.25%
Subsequent Event [Member]
Debt Instrument [Line Items]
Debt Covenant, Debt to EBITDA Ratio, Maximum						6.75	7.00		6.50
Debt Covenant, Interest Coverage Ratio, Minimum										2.25
Scenario, Forecast [Member] \| Senior unsecured due in October 2019 - 6.75% [Member]
Debt Instrument [Line Items]
Extinguishment of Debt, Amount			$ 99.0
Make Whole Premium			$ 1.5
Scenario, Forecast [Member] \| Ten Year Senior Unsecured Bonds At435 Maturing At April152029 [Member]
Debt Instrument [Line Items]
Proceeds from Issuance of Long-term Debt		$ 400.0
Debt instrument interest percentage		4.35%
Scenario, Forecast [Member] \| Ten Year Senior Unsecured Notes At725 Maturing At October152021 [Member]
Debt Instrument [Line Items]
Extinguishment of Debt, Amount	$ 400.0
Long-term Debt, Gross	$ 380.0