Condensed Consolidated Balance Sheets - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 65.4		$ 65.4		$ 24.5
Restricted cash	22.0		22.0		0.4
Accounts receivable, net	95.5		95.5		64.6
Inventories	10.7		10.7		12.7
Taxes applicable to subsequent years	17.1		17.1		71.3
Regulatory assets, current	34.0		34.0		23.9
Other prepayments and current assets	11.5		11.5		12.6
Assets Held-for-sale, Not Part of Disposal Group, Current	9.5		9.5		315.6
Total current assets	265.7		265.7		525.6
Property, plant & equipment:
Property, plant & equipment	1,586.5		1,586.5		1,542.4
Less: Accumulated depreciation and amortization	(297.1)		(297.1)		(269.1)
Property, plant and equipment, net of depreciation	1,289.4		1,289.4		1,273.3
Construction work in process	31.3		31.3		46.5
Total net property, plant & equipment	1,320.7		1,320.7		1,319.8
Other non-current assets:
Regulatory assets, non-current	150.6		150.6		163.2
Intangible assets, net of amortization	16.6		16.6		18.8
Other deferred assets	23.9		23.9		13.8
Disposal Group, Including Discontinued Operation, Assets, Noncurrent	8.0		8.0		8.0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	(0.2)	$ (0.1)	(0.6)	$ (0.5)
Total other non-current assets	199.1		199.1		203.8
Total assets	1,785.5		1,785.5		2,049.2
Current liabilities:
Current portion of long-term debt	4.6		4.6		4.6
Short-term debt	0.0		0.0		10.0
Accounts payable	46.9		46.9		48.9
Accrued taxes	74.9		74.9		77.3
Accrued interest	30.1		30.1		16.4
Security deposits	20.5		20.5		21.8
Regulatory liabilities, current	36.1		36.1		14.8
Other current liabilities	14.0		14.0		16.2
Liabilities Held for Sale, Current	19.9		19.9		66.9
Total current liabilities	247.0		247.0		276.9
Non-current liabilities:
Long-term debt	1,471.4		1,471.4		1,700.2
Deferred taxes	110.6		110.6		128.6
Taxes payable	3.5		3.5		74.8
Regulatory liabilities, non-current	239.7		239.7		221.2
Pension, retiree and other benefits	82.7		82.7		90.3
Asset Retirement Obligations, Noncurrent	13.5	132.5	13.5	132.5	15.1
Other deferred credits	8.0		8.0		8.5
Disposal Group, Including Discontinued Operation, Liabilities, Noncurrent	118.6		118.6		117.9
Total non-current liabilities	2,048.0		2,048.0		2,356.6
Commitments and contingencies
Common shareholder's equity:
Common stock	0.0		0.0		0.0
Other paid-in capital	2,360.8		2,360.8		2,330.4
Accumulated other comprehensive income	2.8		2.8		0.8
Retained earnings/ (deficit)	(2,873.1)		(2,873.1)		(2,915.5)
Total common shareholder's equity	(509.5)		(509.5)		(584.3)
Total liabilities and shareholder's equity	1,785.5		1,785.5		2,049.2
THE DAYTON POWER AND LIGHT COMPANY [Member]
Current assets:
Cash and cash equivalents	10.7		10.7		5.2
Restricted cash	2.0		2.0		0.4
Accounts receivable, net	103.0		103.0		70.8
Inventories	7.5		7.5		7.3
Taxes applicable to subsequent years	17.1		17.1		71.1
Regulatory assets, current	34.0		34.0		23.9
Other prepayments and current assets	11.7		11.7		14.6
Total current assets	186.0		186.0		193.3
Property, plant & equipment:
Property, plant & equipment	2,253.8		2,253.8		2,247.2
Less: Accumulated depreciation and amortization	(980.3)		(980.3)		(987.3)
Property, plant and equipment, net of depreciation	1,273.5		1,273.5		1,259.9
Construction work in process	29.8		29.8		41.5
Total net property, plant & equipment	1,303.3		1,303.3		1,301.4
Other non-current assets:
Regulatory assets, non-current	150.6		150.6		163.2
Intangible assets, net of amortization	15.4		15.4		18.8
Other deferred assets	23.1		23.1		12.7
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	(0.2)	(0.2)	(0.5)	(0.5)
Total other non-current assets	189.1		189.1		194.7
Total assets	1,678.4		1,678.4		1,689.4
Current liabilities:
Current portion of long-term debt	4.6		4.6		4.6
Short-term debt	0.0		0.0		10.0
Accounts payable	44.1		44.1		46.6
Accrued taxes	82.5		82.5		70.1
Accrued interest	0.7		0.7		0.8
Security deposits	20.5		20.5		21.8
Regulatory liabilities, current	36.1		36.1		14.8
Other current liabilities	11.2		11.2		12.9
Total current liabilities	199.7		199.7		181.6
Non-current liabilities:
Long-term debt	582.1		582.1		642.0
Deferred taxes	125.3		125.3		131.0
Taxes payable	4.8		4.8		75.8
Regulatory liabilities, non-current	239.7		239.7		221.2
Pension, retiree and other benefits	83.5		83.5		91.1
Asset Retirement Obligation	4.7	$ 131.0	4.7	$ 131.0	8.0
Other deferred credits	7.6		7.6		8.0
Total non-current liabilities	1,047.7		1,047.7		1,177.1
Commitments and contingencies
Common shareholder's equity:
Common stock	0.4		0.4		0.4
Other paid-in capital	721.8		721.8		685.8
Accumulated other comprehensive income	(34.8)		(34.8)		(36.2)
Retained earnings/ (deficit)	(256.4)		(256.4)		(319.3)
Total common shareholder's equity	431.0		431.0		330.7
Total liabilities and shareholder's equity	$ 1,678.4		$ 1,678.4		$ 1,689.4