Consolidated Statements of Cash Flows (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012 THE DAYTON POWER AND LIGHT COMPANY [Member]	Mar. 31, 2011 THE DAYTON POWER AND LIGHT COMPANY [Member]	Mar. 31, 2012 Successor [Member]	Mar. 31, 2011 Predecessor [Member]
Cash flows from operating activities:
Net income	$ 38.1	$ 52.7	$ 21.7	$ 43.5
Adjustments to reconcile Net income to Net cash provided by operating activities:
Depreciation and amortization	34.7	33.1	31.4	35.1
Amortization of other assets			27.8	0
Amortization of debt market value adjustments			(4.7)	0
Deferred income taxes	(2.4)	33.3	(9.2)	33.7
Charge for early redemption of debt				15.3
Changes in certain assets and liabilities:
Accounts receivable	(0.6)	11.9	(3.4)	11.9
Inventories	(2.0)	1.3	(1.4)	0.4
Taxes applicable to subsequent years	21.5	15.7	22.9	15.9
Deferred regulatory costs, net	7.1	12.8	7.2	12.8
Accounts payable	(2.2)	(4.0)	(1.8)	(5.1)
Accrued taxes payable	(15.0)	(28.9)	(21.6)	(28.4)
Accrued interest payable	7.5	7.6	29.1	(1.2)
Pension, retiree and other benefits	2.1	(41.2)	2.1	(41.2)
Unamortized investment tax credit	(0.6)	(0.7)		(0.7)
Insurance and claims costs			0.8	2.2
Payment to former warrant holders			(9.0)	0
Other	1.4	(9.6)	(6.3)	(2.2)
Net cash provided by operating activities	89.6	84.0	85.6	92.0
Cash flows from investing activities:
Capital expenditures	(53.2)	(42.4)	(54.0)	(43.0)
Purchase of MC Squared				(8.2)
Purchases of short-term investments and securities				(1.7)
Sales of short-term investments and securities				60.8
Other	0	2.0		2.1
Net cash used for investing activities	(53.2)	(40.4)	(54.0)	10.0
Cash flows from financing activities:
Dividends paid on common stock	(45.0)	(70.0)	(45.0)	(37.8)
Dividends paid on preferred stock	(0.2)	(0.2)
Early redemption of Capital Trust II debt				(122.0)
Premium paid for early redemption of debt				(12.2)
Payment of MC Squared debt				(13.5)
Withdrawals from revolving credit facilities	0	50.0		50.0
Repayments of borrowings from revolving credit facilities	0	(20.0)		(20.0)
Contributions to additional paid-in capital from parent			2.0	0
Net cash used for financing activities	(45.2)	(40.2)	(43.0)	(155.5)
Cash and cash equivalents:
Net change	(8.8)	3.4	(11.4)	(53.5)
Balance at beginning of period	32.2	54.0	173.5	124.0
Cash and cash equivalents at end of period	23.4	57.4	162.1	70.5
Supplemental cash flow information:
Interest paid, net of amounts capitalized	2.4	2.3	5.7	18.1
Income taxes paid, net	6.1	0	7.0	0
Non-cash financing and investing activities:
Accruals for capital expenditures	24.1	18.3	24.1	18.3
Long-term liability incurred for purchase of assets	$ 0	$ 18.7		$ 18.7