Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Cash flows from operating activities:
Net income/ (loss)	$ 59.0	$ (116.8)
Adjustments to reconcile net income / (loss) to net cash from operating activities:
Depreciation and amortization	104.1	103.7
Amortization of intangibles	0.0	0.9
Amortization of debt market value adjustments	(1.1)	0.1
Deferred income taxes	(20.5)	(2.5)
Goodwill impairment	0.0	135.8
Fixed-asset impairment	0.0	11.5
Changes in certain assets and liabilities:
Accounts receivable	48.8	12.7
Inventories	3.1	(3.6)
Prepaid taxes	(0.6)	0.5
Taxes applicable to subsequent years	58.2	52.1
Deferred regulatory costs, net	27.6	4.8
Accounts payable	(15.9)	7.2
Accrued taxes payable	(39.2)	(27.5)
Accrued interest payable	3.7	14.5
Security deposits	19.4	0.5
Pension, retiree and other benefits	1.0	(5.2)
Other	12.8	(14.3)
Net cash provided by operating activities	260.4	174.4
Cash flows from investing activities:
Capital expenditures	(93.5)	(81.6)
Proceeds from sale of business	1.3	0.0
Increase / (decrease) in restricted cash	3.2	(9.0)
Other investing activities, net	0.4	1.1
Net cash used by investing activities	(89.2)	(93.1)
Cash flows from financing activities:
Payments of deferred financing costs	(5.6)	(0.3)
Issuance of long-term debt	325.0	0.0
Borrowings from revolving credit facilities	70.0	115.0
Repayment of borrowings from revolving credit facilities	(60.0)	(115.0)
Retirement of long-term debt	(474.5)	(30.1)
Other financing activities, net	(0.1)	0.0
Net cash used by financing activities	(145.2)	(30.4)
Cash and cash equivalents:
Net change	26.0	50.9
Balance at beginning of period	17.0	53.2
Cash and cash equivalents at end of period	43.0	104.1
Supplemental cash flow information:
Interest paid, net of amounts capitalized	77.3	73.8
Income taxes paid / (refunded), net	0.8	0.2
Non-cash financing and investing activities:
Accruals for capital expenditures	12.6	6.7
THE DAYTON POWER AND LIGHT COMPANY [Member]
Cash flows from operating activities:
Net income/ (loss)	75.9	76.5
Adjustments to reconcile net income / (loss) to net cash from operating activities:
Depreciation and amortization	103.5	108.2
Deferred income taxes	(14.2)	2.9
Changes in certain assets and liabilities:
Accounts receivable	37.3	4.8
Inventories	3.0	(3.5)
Prepaid taxes	(0.4)	0.2
Taxes applicable to subsequent years	56.4	50.5
Deferred regulatory costs, net	27.6	4.8
Accounts payable	(20.0)	7.9
Accrued taxes payable	(29.1)	(40.8)
Accrued interest payable	(8.8)	(5.7)
Pension, retiree and other benefits	1.0	(5.2)
Other	15.5	(11.4)
Net cash provided by operating activities	247.7	189.2
Cash flows from investing activities:
Capital expenditures	(91.2)	(78.6)
Insurance proceeds	4.3	0.4
Increase / (decrease) in restricted cash	3.2	(9.4)
Other investing activities, net	0.4	1.1
Net cash used by investing activities	(83.9)	(90.1)
Cash flows from financing activities:
Payments of deferred financing costs	(3.3)	(0.2)
Issuance of long-term debt	200.0	0.0
Dividends paid on common stock to parent	(50.0)	(90.0)
Borrowings from revolving credit facilities	50.0	0.0
Issuance of notes payable - related party	0.0	15.0
Repayment of notes payable - related party	0.0	(15.0)
Dividends paid on preferred stock	(0.7)	(0.7)
Repayment of borrowings from revolving credit facilities	(40.0)	0.0
Retirement of long-term debt	(314.5)	(0.1)
Net cash used by financing activities	(158.5)	(91.0)
Cash and cash equivalents:
Net change	5.3	8.1
Balance at beginning of period	5.4	22.9
Cash and cash equivalents at end of period	10.7	31.0
Supplemental cash flow information:
Interest paid, net of amounts capitalized	26.8	26.1
Income taxes paid / (refunded), net	0.8	0.2
Non-cash financing and investing activities:
Accruals for capital expenditures	12.6	6.7
Emission Allowances [Member]
Cash flows from investing activities:
Purchase of intangible assets	0.0	(0.2)
Emission Allowances [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Cash flows from investing activities:
Purchase of intangible assets	0.0	(0.2)
Renewable Energy Credits [Member]
Cash flows from investing activities:
Purchase of intangible assets	(0.6)	(3.4)
Renewable Energy Credits [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Cash flows from investing activities:
Purchase of intangible assets	$ (0.6)	$ (3.4)