Condensed Consolidated Balance Sheets - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 61.2		$ 61.2		$ 24.5
Restricted cash	7.2		7.2		0.4
Accounts receivable, net	94.3		94.3		64.6
Inventories	11.6		11.6		12.7
Taxes applicable to subsequent years	34.8		34.8		71.3
Regulatory assets, current	26.5		26.5		23.9
Other prepayments and current assets	10.9		10.9		12.6
Assets Held-for-sale, Not Part of Disposal Group, Current	29.3		29.3		315.6
Total current assets	275.8		275.8		525.6
Property, plant & equipment:
Property, plant & equipment	1,554.6		1,554.6		1,542.4
Less: Accumulated depreciation and amortization	(268.8)		(268.8)		(269.1)
Property, plant and equipment, net of depreciation	1,285.8		1,285.8		1,273.3
Construction work in process	29.3		29.3		46.5
Total net property, plant & equipment	1,315.1		1,315.1		1,319.8
Other non-current assets:
Regulatory assets, non-current	151.0		151.0		163.2
Intangible assets, net of amortization	17.7		17.7		18.8
Other deferred assets	25.4		25.4		13.8
Disposal Group, Including Discontinued Operation, Assets, Noncurrent	7.5		7.5		8.0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	0.0	$ (0.2)	(0.4)	$ (0.3)
Total other non-current assets	201.6		201.6		203.8
Total assets	1,792.5		1,792.5		2,049.2
Current liabilities:
Current portion of long-term debt	4.6		4.6		4.6
Short-term debt	10.0		10.0		10.0
Accounts payable	50.7		50.7		48.9
Accrued taxes	70.1		70.1		77.3
Accrued interest	14.9		14.9		16.4
Security deposits	20.7		20.7		21.8
Regulatory liabilities, current	32.4		32.4		14.8
Insurance and claims costs	2.7		2.7		3.0
Other current liabilities	13.0		13.0		13.2
Liabilities Held for Sale, Current	33.9		33.9		66.9
Total current liabilities	253.0		253.0		276.9
Non-current liabilities:
Long-term debt	1,471.6		1,471.6		1,700.2
Deferred taxes	110.9		110.9		128.6
Taxes payable	38.4		38.4		74.8
Regulatory liabilities, non-current	233.9		233.9		221.2
Pension, retiree and other benefits	83.0		83.0		90.3
Asset Retirement Obligations, Noncurrent	11.9	135.6	11.9	135.6	15.1
Other deferred credits	8.0		8.0		8.5
Disposal Group, Including Discontinued Operation, Liabilities, Noncurrent	115.9		115.9		117.9
Total non-current liabilities	2,073.6		2,073.6		2,356.6
Commitments and contingencies
Common shareholder's equity:
Common stock	0.0		0.0		0.0
Other paid-in capital	2,357.2		2,357.2		2,330.4
Accumulated other comprehensive income	2.8		2.8		0.8
Retained earnings/ (deficit)	(2,894.1)		(2,894.1)		(2,915.5)
Total common shareholder's equity	(534.1)		(534.1)		(584.3)
Total liabilities and shareholder's equity	1,792.5		1,792.5		2,049.2
THE DAYTON POWER AND LIGHT COMPANY [Member]
Current assets:
Cash and cash equivalents	23.0		23.0		5.2
Restricted cash	7.2		7.2		0.4
Accounts receivable, net	100.2		100.2		70.8
Inventories	7.7		7.7		7.3
Taxes applicable to subsequent years	34.7		34.7		71.1
Regulatory assets, current	26.5		26.5		23.9
Other prepayments and current assets	11.6		11.6		14.6
Total current assets	210.9		210.9		193.3
Property, plant & equipment:
Property, plant & equipment	2,243.7		2,243.7		2,247.2
Less: Accumulated depreciation and amortization	(971.7)		(971.7)		(987.3)
Property, plant and equipment, net of depreciation	1,272.0		1,272.0		1,259.9
Construction work in process	25.7		25.7		41.5
Total net property, plant & equipment	1,297.7		1,297.7		1,301.4
Other non-current assets:
Regulatory assets, non-current	151.0		151.0		163.2
Intangible assets, net of amortization	16.5		16.5		18.8
Other deferred assets	24.5		24.5		12.7
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	(0.2)	(0.2)	(0.5)	(0.4)
Total other non-current assets	192.0		192.0		194.7
Total assets	1,700.6		1,700.6		1,689.4
Current liabilities:
Current portion of long-term debt	4.6		4.6		4.6
Short-term debt	10.0		10.0		10.0
Accounts payable	47.6		47.6		46.6
Accrued taxes	74.7		74.7		70.1
Accrued interest	0.9		0.9		0.8
Security deposits	20.7		20.7		21.8
Regulatory liabilities, current	32.4		32.4		14.8
Other current liabilities	12.7		12.7		12.9
Total current liabilities	203.6		203.6		181.6
Non-current liabilities:
Long-term debt	582.7		582.7		642.0
Deferred taxes	125.5		125.5		131.0
Taxes payable	39.6		39.6		75.8
Regulatory liabilities, non-current	233.9		233.9		221.2
Pension, retiree and other benefits	83.8		83.8		91.1
Unamortized investment tax credit	0.7		0.7		0.9
Asset Retirement Obligation	4.7	$ 132.3	4.7	$ 132.3	8.0
Other deferred credits	7.0		7.0		7.1
Total non-current liabilities	1,077.9		1,077.9		1,177.1
Commitments and contingencies
Common shareholder's equity:
Common stock	0.4		0.4		0.4
Other paid-in capital	741.7		741.7		685.8
Accumulated other comprehensive income	(35.4)		(35.4)		(36.2)
Retained earnings/ (deficit)	(287.6)		(287.6)		(319.3)
Total common shareholder's equity	419.1		419.1		330.7
Total liabilities and shareholder's equity	$ 1,700.6		$ 1,700.6		$ 1,689.4