Related Party Transactions (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended		12 Months Ended
	Dec. 31, 2015	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Related Party Transaction [Line Items]
Charges for services provided		$ 11.5	$ 9.8	$ 23.1	$ 19.6
Sales to related party		1.1	2.8	2.3	3.9
Net advance / (payable) to the Service Company	$ (0.5)	(1.1)		(1.1)		$ (0.5)
Investment in trust	$ 0.3	0.3		0.3		0.3
Debt Instrument, Interest Rate, Stated Percentage	2.67%
Notes Payable, Related Parties	$ 35.0	0.0		0.0		35.0
Note to DPL Capital Trust II Maturing in September 2031 - 8.125% [Member]
Related Party Transaction [Line Items]
Note payable to trust	15.6	15.6		15.6		15.6
Prepaid Expenses and Other Current Assets [Member]
Related Party Transaction [Line Items]
Accounts Receivable, Related Parties, Current	50.5	78.9		78.9		50.5
Charges for health, welfare and benefit plans [Member] | AES affiliates [Member]
Related Party Transaction [Line Items]
Transactions with other AES affiliates		(2.4)	4.2	1.7	8.2
THE DAYTON POWER AND LIGHT COMPANY [Member]
Related Party Transaction [Line Items]
Charges for services provided		10.9	8.3	19.8	16.7
Sales to related party		1.0	2.8	2.2	3.9
Premiums paid for insurance services provided by MVIC		(0.8)	(0.8)	(1.7)	(1.6)
Expense recoveries for services provided to DPLER		0.0	0.6	0.0	1.3
Net advance / (payable) to the Service Company	(0.5)	(1.1)		(1.1)		(0.5)
Gain on termination of contract		0.0	0.0	27.7	0.0
Notes Payable, Related Parties				(5.0)	0.0	(35.0)
THE DAYTON POWER AND LIGHT COMPANY [Member] | Prepaid Expenses and Other Current Assets [Member]
Related Party Transaction [Line Items]
Accounts Receivable, Related Parties, Current	$ 1.5	10.8		10.8		$ 1.5
THE DAYTON POWER AND LIGHT COMPANY [Member] | Insurance Proceeds Received [Member] | AES affiliates [Member]
Related Party Transaction [Line Items]
Transactions with other AES affiliates		0.0	2.3	0.2	3.8
THE DAYTON POWER AND LIGHT COMPANY [Member] | Charges for health, welfare and benefit plans [Member] | AES affiliates [Member]
Related Party Transaction [Line Items]
Transactions with other AES affiliates		(2.4)	3.9	1.7	7.8
THE DAYTON POWER AND LIGHT COMPANY [Member] | Dpler [Member]
Related Party Transaction [Line Items]
Sales to related party		$ 0.0	$ 68.3	$ 0.0	$ 179.0