Consolidated Statements of Cash Flows (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Cash flows from operating activities:
Net income	$ 19.9	$ 21.7
Adjustments to reconcile Net income to Net cash provided by operating activities:
Depreciation and amortization	31.8	31.4
Amortization of intangibles	1.8	27.8
Amortization of debt market value adjustments	(4.8)	(4.7)
Deferred income taxes	23.3	(9.2)
Changes in certain assets and liabilities:
Accounts receivable	19.5	(3.4)
Inventories	(4.4)	(0.6)
Taxes applicable to subsequent years	17.2	22.9
Deferred regulatory costs, net	3.6	7.2
Accounts payable	2.7	(1.8)
Accrued taxes payable	(33.7)	(21.6)
Accrued interest payable	23.7	29.1
Pension, retiree and other benefits	3.2	2.1
Insurance and claims costs	1.0	0.8
Other	1.4	2.3
Net cash provided by operating activities	106.2	104.0
Cash flows from investing activities:
Capital expenditures	(33.8)	(54.0)
Increase (Decrease) in Restricted Cash	(12.7)	(8.7)
Net cash used for investing activities	(47.0)	(63.4)
Cash flows from financing activities:
Dividends paid on common stock		(45.0)
Payment to former warrant holders		(9.0)
Contributions to additional paid-in capital from parent		2.0
Net cash used for financing activities		(52.0)
Cash and cash equivalents:
Net change	59.2	(11.4)
Balance at beginning of period	192.1	173.5
Cash and cash equivalents at end of period	251.3	162.1
Supplemental cash flow information:
Interest paid, net of amounts capitalized	11.3	5.7
Income taxes paid/(refund), net	(20.0)	7.0
Non-cash financing and investing activities:
Accruals for capital expenditures	10.6	24.1
THE DAYTON POWER AND LIGHT COMPANY [Member]
Cash flows from operating activities:
Net income	30.2	38.1
Adjustments to reconcile Net income to Net cash provided by operating activities:
Depreciation and amortization	33.6	34.7
Deferred income taxes	22.9	(2.4)
Changes in certain assets and liabilities:
Accounts receivable	13.2	(0.6)
Inventories	(4.3)	(2.0)
Taxes applicable to subsequent years	16.7	21.5
Deferred regulatory costs, net	3.6	7.1
Accounts payable	2.7	(2.2)
Accrued taxes payable	(25.3)	(15.0)
Accrued interest payable	2.3	7.5
Pension, retiree and other benefits	3.2	2.1
Unamortized investment tax credit	(0.6)	(0.6)
Other	3.6	10.8
Net cash provided by operating activities	101.8	99.0
Cash flows from investing activities:
Capital expenditures	(33.6)	(53.2)
Increase (Decrease) in Restricted Cash	(12.7)	(8.7)
Net cash used for investing activities	(46.8)	(62.6)
Cash flows from financing activities:
Dividends paid on common stock	(55.0)	(45.0)
Dividends paid on preferred stock	(0.2)	(0.2)
Net cash used for financing activities	(55.2)	(45.2)
Cash and cash equivalents:
Net change	(0.2)	(8.8)
Balance at beginning of period	28.5	32.2
Cash and cash equivalents at end of period	28.3	23.4
Supplemental cash flow information:
Interest paid, net of amounts capitalized	7.9	2.4
Income taxes paid/(refund), net	(20.0)	6.1
Non-cash financing and investing activities:
Accruals for capital expenditures	10.6	24.1
Renewable Energy Certificates [Member]
Cash flows from investing activities:
Payments to Acquire Intangible Assets	(0.5)	(0.7)
Renewable Energy Certificates [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Cash flows from investing activities:
Payments to Acquire Intangible Assets	$ (0.5)	$ (0.7)