Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Cash flows from operating activities:
Net income	$ (89.9)	$ 59.0
Adjustments to reconcile net income / (loss) to net cash from operating activities:
Depreciation and amortization	100.3	104.1
Amortization of debt market value adjustments	0.1	(1.1)
Charge for early retirement of debt	3.1	2.1
Deferred income taxes	(101.4)	(20.5)
Impairment of Long-Lived Assets Held-for-use	235.5	0.0
Gain on sale of business	(49.2)	0.0
Changes in certain assets and liabilities:
Accounts receivable	23.6	48.8
Inventories	29.1	3.1
Prepaid taxes	0.2	(0.6)
Taxes applicable to subsequent years	61.5	58.2
Deferred regulatory costs, net	19.5	27.6
Accounts payable	(10.2)	(15.9)
Accrued taxes payable	(34.2)	(39.2)
Accrued interest payable	13.9	3.7
Security deposits	(0.6)	19.4
Pension, retiree and other benefits	(2.2)	1.0
Other	(0.5)	10.7
Net cash provided by operating activities	198.6	260.4
Cash flows from investing activities:
Capital expenditures	(109.8)	(93.5)
Proceeds from sale of business	75.5	1.3
Insurance proceeds	5.2	0.0
Purchase of intangible assets	(0.3)	(0.6)
Decrease in restricted cash	5.5	3.2
Other investing activities, net	0.8	0.4
Net cash used in investing activities	(23.1)	(89.2)
Cash flows from financing activities:
Payments of Deferred Finance Costs	(8.0)	(5.6)
Proceeds from Issuance of Long-term Debt	442.8	325.0
Retirement of long-term debt	(520.8)	(474.5)
Borrowings from revolving credit facilities	0.0	70.0
Repayment of borrowings from revolving credit facilities	0.0	(60.0)
Proceeds from (Payments for) Other Financing Activities	(0.1)	(0.1)
Net cash used in financing activities	(86.1)	(145.2)
Cash and cash equivalents:
Net change	89.4	26.0
Balance at beginning of period	32.4	17.0
Cash and cash equivalents at end of period	121.8	43.0
Supplemental cash flow information:
Interest paid, net of amounts capitalized	61.1	77.3
Income taxes paid / (refunded), net	0.3	0.8
Non-cash financing and investing activities:
Accruals for capital expenditures	15.9	12.6
THE DAYTON POWER AND LIGHT COMPANY [Member]
Cash flows from operating activities:
Net income	(467.8)	75.9
Adjustments to reconcile net income / (loss) to net cash from operating activities:
Depreciation and amortization	95.2	103.5
Charge for early retirement of debt	0.5	5.0
Deferred income taxes	(314.2)	(14.2)
Impairment of Long-Lived Assets Held-for-use	857.1	0.0
Changes in certain assets and liabilities:
Accounts receivable	(11.0)	37.3
Inventories	29.4	3.0
Prepaid taxes	2.7	(0.4)
Taxes applicable to subsequent years	59.9	56.4
Deferred regulatory costs, net	19.5	27.6
Accounts payable	(13.5)	(20.0)
Accrued taxes payable	(43.2)	(29.1)
Accrued interest payable	(3.3)	(8.8)
Pension, retiree and other benefits	(2.2)	1.0
Other	11.3	10.5
Net cash provided by operating activities	220.4	247.7
Cash flows from investing activities:
Capital expenditures	(98.3)	(91.2)
Insurance proceeds	5.6	4.3
Purchase of intangible assets	(0.3)	(0.6)
Decrease in restricted cash	5.5	3.2
Other investing activities, net	0.9	0.4
Net cash used in investing activities	(86.6)	(83.9)
Cash flows from financing activities:
Payments of Deferred Finance Costs	(8.0)	(3.3)
Proceeds from Issuance of Long-term Debt	442.8	200.0
Retirement of long-term debt	(445.3)	(314.5)
Borrowings from revolving credit facilities	0.0	50.0
Repayment of borrowings from revolving credit facilities	0.0	(40.0)
Dividends paid on common stock to parent	0.0	(50.0)
Issuance of short-term debt - related party	5.0	0.0
Repayment of short-term debt - related party	(40.0)	0.0
Dividends paid on preferred stock	(0.7)	(0.7)
Proceeds from (Payments for) Other Financing Activities	(0.1)	0.0
Net cash used in financing activities	(46.3)	(158.5)
Cash and cash equivalents:
Net change	87.5	5.3
Balance at beginning of period	5.4	5.4
Cash and cash equivalents at end of period	92.9	10.7
Supplemental cash flow information:
Interest paid, net of amounts capitalized	16.3	26.8
Income Taxes Paid, Net	0.3	0.8
Non-cash financing and investing activities:
Accruals for capital expenditures	10.1	12.6
Subsidiary of Common Parent [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Non-cash financing and investing activities:
Equity Settlement of Related Party Payable	$ 7.5	$ 0.0