Consolidated Statements of Cash Flows (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2012 THE DAYTON POWER AND LIGHT COMPANY [Member]	Jun. 30, 2011 THE DAYTON POWER AND LIGHT COMPANY [Member]	Jun. 30, 2012 Successor [Member]	Jun. 30, 2011 Predecessor [Member]
Cash flows from operating activities:
Net income	$ 69.4	$ 83.5	$ 26.6	$ 75.2
Adjustments to reconcile Net income to Net cash provided by operating activities:
Depreciation and amortization	70.8	66.5	61.1	70.2
Amortization of other assets			56.4	0
Amortization of debt market value adjustments			(9.5)	0
Deferred income taxes	3.3	37.2	(6.9)	37.5
Charge for early redemption of debt				15.3
Changes in certain assets and liabilities:
Accounts receivable	19.5	25.5	9.6	19.5
Inventories	(2.5)	1.5	(1.2)	1.2
Prepaid taxes	0.4	(19.2)	0.3	(20.7)
Taxes applicable to subsequent years	38.4	31.4	40.7	31.8
Deferred regulatory costs, net	(0.1)	8.9	0.1	8.9
Accounts payable	6.5	(7.8)	7.9	(5.9)
Accrued taxes payable	(46.8)	(32.3)	(50.6)	(33.4)
Accrued interest payable	5.2	5.3	1.5	2.0
Pension, retiree and other benefits	4.6	(42.7)	4.6	(42.7)
Unamortized investment tax credit	(1.3)	(1.4)	(0.1)	(1.4)
Insurance and claims costs				3.7
Other	6.1	6.8	2.6	23.9
Net cash provided by operating activities	173.5	163.2	143.1	185.1
Cash flows from investing activities:
Capital expenditures	(109.5)	(90.8)	(110.5)	(91.4)
Purchase of MC Squared				(8.2)
Purchases of short-term investments and securities				(1.7)
Sales of short-term investments and securities				70.9
Other	0	1.7		1.8
Net cash used for investing activities	(109.5)	(89.1)	(110.5)	(28.6)
Cash flows from financing activities:
Dividends paid on common stock	(70.0)	(115.0)	(45.0)	(76.4)
Dividends paid on preferred stock	(0.4)	(0.4)
Payment to former warrant holders			(9.0)	0
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)
Payment of long-term debt	(0.1)	0	(0.1)	0
Withdrawals from revolving credit facilities	0	50.0		50.0
Repayments of borrowings from revolving credit facilities	0	(50.0)		(50.0)
Contributions to additional paid-in capital from parent			0.3	0
Exercise of stock options				1.4
Exercise of warrants				14.7
Tax impact related to exercise of stock options				0.3
Net cash used for financing activities	(70.5)	(115.4)	(53.8)	(207.7)
Cash and cash equivalents:
Net change	(6.5)	(41.3)	(21.2)	(51.2)
Balance at beginning of period	32.2	54.0	173.5	124.0
Cash and cash equivalents at end of period	25.7	12.7	152.3	72.8
Supplemental cash flow information:
Interest paid, net of amounts capitalized	14.4	14.6	66.7	30.3
Income taxes paid, net	16.6	24.1	21.6	24.7
Non-cash financing and investing activities:
Accruals for capital expenditures	25.3	22.6	25.3	22.6
Long-term liability incurred for purchase of assets	$ 0	$ 18.7		$ 18.7