Regulatory Assets and Liabilities (Schedule of Regulatory Assets and Liabilities) (Details) - USD ($)	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015
Total current regulatory assets	$ 100,000	$ 14,400,000
Total non-current regulatory assets	203,900,000	179,900,000
Total regulatory assets	204,000,000	194,300,000
Total current regulatory liabilities	33,700,000	24,400,000
Total non-current regulatory liabilities	130,400,000	127,000,000
Total regulatory liabilities	164,100,000	151,400,000
Energy efficiency program [Member]
Total current regulatory liabilities	14,100,000	9,200,000
Competitive bidding [Member]
Total current regulatory liabilities	16,100,000	9,100,000
Transmission costs [Member]
Total current regulatory liabilities	3,300,000	3,700,000
Reconciliation rider [Member]
Total current regulatory liabilities	0	2,100,000
Other miscellaneous [Member]
Total current regulatory liabilities	200,000	300,000
Estimated costs of removal - regulated property [Member]
Total non-current regulatory liabilities	126,500,000	121,800,000
Postretirement benefits [Member]
Total non-current regulatory liabilities	3,900,000	5,200,000
THE DAYTON POWER AND LIGHT COMPANY [Member]
Total current regulatory assets	100,000	14,400,000
Total non-current regulatory assets	203,900,000	179,900,000
Total regulatory assets	204,000,000	194,300,000
Total current regulatory liabilities	33,700,000	24,400,000
Total non-current regulatory liabilities	130,400,000	127,000,000
Total regulatory liabilities	164,100,000	151,400,000
THE DAYTON POWER AND LIGHT COMPANY [Member] \| Energy efficiency program [Member]
Total current regulatory liabilities	14,100,000	9,200,000
THE DAYTON POWER AND LIGHT COMPANY [Member] \| Competitive bidding [Member]
Total current regulatory liabilities	16,100,000	9,100,000
THE DAYTON POWER AND LIGHT COMPANY [Member] \| Transmission costs [Member]
Total current regulatory liabilities	3,300,000	3,700,000
THE DAYTON POWER AND LIGHT COMPANY [Member] \| Reconciliation rider [Member]
Total current regulatory liabilities	0	2,100,000
THE DAYTON POWER AND LIGHT COMPANY [Member] \| Other miscellaneous [Member]
Total current regulatory liabilities	200,000	300,000
THE DAYTON POWER AND LIGHT COMPANY [Member] \| Estimated costs of removal - regulated property [Member]
Total non-current regulatory liabilities	126,500,000	121,800,000
THE DAYTON POWER AND LIGHT COMPANY [Member] \| Postretirement benefits [Member]
Total non-current regulatory liabilities	$ 3,900,000	5,200,000
Fuel and purchased power recovery costs [Member]
Type of Recovery	A
Amortization Through	P2016Y
Total current regulatory assets	$ 0	13,900,000
Fuel and purchased power recovery costs [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member]
Type of Recovery	A
Amortization Through	P2016Y
Total current regulatory assets	$ 0	13,900,000
Economic development costs [Member]
Type of Recovery	A
Amortization Through	P2017Y
Total current regulatory assets	$ 100,000	500,000
Economic development costs [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member]
Type of Recovery	A
Amortization Through	P2017Y
Total current regulatory assets	$ 100,000	500,000
Pension benefits [Member]
Type of Recovery	B
Amortization Through	Ongoing
Total non-current regulatory assets	$ 97,600,000	91,600,000
Pension benefits [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member]
Type of Recovery	B
Amortization Through	Ongoing
Total non-current regulatory assets	$ 97,600,000	91,600,000
Deferred recoverable income taxes [Member]
Type of Recovery	B/C
Amortization Through	Ongoing
Total non-current regulatory assets	$ 35,900,000	36,400,000
Deferred recoverable income taxes [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member]
Type of Recovery	B/C
Amortization Through	Ongoing
Total non-current regulatory assets	$ 35,900,000	36,400,000
Fuel costs [Member]
Type of Recovery	B
Amortization Through	Undetermined
Total non-current regulatory assets	$ 15,400,000	12,700,000
Fuel costs [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member]
Type of Recovery	B
Amortization Through	Undetermined
Total non-current regulatory assets	$ 15,400,000	12,700,000
Unrecovered OVEC charges [Member]
Type of Recovery	D
Amortization Through	Undetermined
Total non-current regulatory assets	$ 21,000,000	10,500,000
Unrecovered OVEC charges [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member]
Type of Recovery	D
Amortization Through	Undetermined
Total non-current regulatory assets	$ 21,000,000	10,500,000
Unamortized loss on reacquired debt [Member]
Type of Recovery	B
Amortization Through	Various
Total non-current regulatory assets	$ 8,000,000	9,000,000
Unamortized loss on reacquired debt [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member]
Type of Recovery	B
Amortization Through	Various
Total non-current regulatory assets	$ 8,000,000	9,000,000
Smart grid and advanced metering infrastructure costs [Member]
Type of Recovery	D
Amortization Through	Undetermined
Total non-current regulatory assets	$ 7,300,000	7,300,000
Smart grid and advanced metering infrastructure costs [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member]
Type of Recovery	D
Amortization Through	Undetermined
Total non-current regulatory assets	$ 7,300,000	7,300,000
Generation separation costs [Member]
Type of Recovery	D
Amortization Through	Undetermined
Total non-current regulatory assets	$ 5,700,000	3,900,000
Generation separation costs [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member]
Amortization Through	Undetermined
Total non-current regulatory assets	$ 5,700,000	3,900,000
Retail settlement system costs [Member]
Type of Recovery	D
Amortization Through	Undetermined
Total non-current regulatory assets	$ 3,100,000	3,100,000
Retail settlement system costs [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member]
Type of Recovery	D
Amortization Through	Undetermined
Total non-current regulatory assets	$ 3,100,000	3,100,000
Consumer education campaign [Member]
Type of Recovery	D
Amortization Through	Undetermined
Total non-current regulatory assets	$ 3,000,000	3,000,000
Consumer education campaign [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member]
Type of Recovery	D
Amortization Through	Undetermined
Total non-current regulatory assets	$ 3,000,000	3,000,000
Rate case costs [Member]
Type of Recovery	D
Amortization Through	Undetermined
Total non-current regulatory assets	$ 6,300,000	1,900,000
Rate case costs [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member]
Type of Recovery	D
Total non-current regulatory assets	$ 6,300,000	1,900,000
Other miscellaneous [Member]
Type of Recovery	D
Amortization Through	Undetermined
Total non-current regulatory assets	$ 600,000	500,000
Other miscellaneous [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member]
Type of Recovery	D
Amortization Through	Undetermined
Total non-current regulatory assets	$ 600,000	$ 500,000

This element represents the type of recovery for each regulatory asset or liability.

No definition available.

Name:	dpl_RegulatoryAssetsTypeOfRecovery
Namespace Prefix:	dpl_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount for the individual regulatory asset as itemized in a table of regulatory assets as of the end of the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 340
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382

+ Details

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

- Definition

Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are expected to be recovered through revenue sources within one year or the normal operating cycle, if longer. Such costs are capitalized if they meet both of the following criteria: a. It is probable that future revenue in an amount at least equal to the capitalized cost will result from inclusion of that cost in allowable costs for rate-making purposes. b. Based on available evidence, the future revenue will be provided to permit recovery of the previously incurred cost rather than to provide for expected levels of similar future costs. If the revenue will be provided through an automatic rate-adjustment clause, this criterion requires that the regulator's intent clearly be to permit recovery of the previously incurred cost.

+ References

+ Details

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

- Definition

Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are not expected to be recovered through revenue sources within one year or the normal operating cycle if longer.

+ References

+ Details

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

- Definition

The end date for recovery of the individual regulatory current asset in a schedule of regulatory current assets.

+ References

+ Details

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

- Definition

The amount for the individual regulatory liability as itemized in a table of regulatory liabilities as of the end of the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 405
-Section 25
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6500807&loc=d3e48068-110394

+ Details

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

- Definition

The amount for the individual regulatory current liability as itemized in a table of regulatory current liabilities as of the end of the period.

+ References

+ Details

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

- Definition

The amount for the individual regulatory noncurrent liability as itemized in a table of regulatory noncurrent liabilities as of the end of the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.24)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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