Consolidated Balance Sheets (USD $) In Millions, unless otherwise specified	Dec. 31, 2011 THE DAYTON POWER AND LIGHT COMPANY [Member]	Dec. 31, 2010 THE DAYTON POWER AND LIGHT COMPANY [Member]	Dec. 31, 2011 Successor [Member]	Dec. 31, 2010 Predecessor [Member]
Current assets:
Cash and cash equivalents	$ 32.2	$ 54.0	$ 173.5	$ 124.0
Short-term investments			0	69.3
Accounts receivable, net (Note 3)	178.5	178.0	219.1	215.5
Inventories (Note 3)	123.1	111.4	125.8	112.6
Taxes applicable to subsequent years	71.9	62.8	76.5	63.7
Regulatory assets, current (Note 4)	17.7	22.0	20.2	22.0
Other prepayments and current assets	25.0	42.7	36.2	40.6
Total current assets	448.4	470.9	651.3	647.7
Property, plant and equipment:
Property, plant and equipment	5,277.9	5,093.7	2,431.0	5,353.6
Less: Accumulated depreciation and amortization	(2,568.9)	(2,453.1)	(7.5)	(2,555.2)
Property, plant and equipment, net of depreciation	2,709.0	2,640.6	2,423.5	2,798.4
Construction work in process	150.7	119.6	152.3	119.7
Total net property, plant and equipment	2,859.7	2,760.2	2,575.8	2,918.1
Other noncurrent assets:
Regulatory assets, non-current (Note 4)	177.8	167.0	177.8	167.0
Goodwill			2,489.3	0
Intangible asset, net of amortization (Note 6)	6.5	2.7	161.5	2.7
Other deferred assets	33.3	74.6	51.8	77.8
Total other noncurrent assets	217.6	244.3	2,880.4	247.5
Total Assets	3,525.7	3,475.4	6,107.5	3,813.3
Current liabilities:
Current portion - long-term debt (Note 7)	0.4	0.1	0.4	297.5
Accounts payable	106.0	95.7	111.1	98.7
Accrued taxes	72.8	66.6	76.3	68.1
Accrued interest	7.9	7.7	30.2	18.4
Customer security deposits	15.8	18.7	15.9	18.7
Regulatory liabilities, current (Note 4)	0	10.0	0.6	10.0
Other current liabilities	41.4	36.0	56.1	43.2
Total current liabilities	244.3	234.8	290.6	554.6
Noncurrent liabilities:
Long-term debt (Note 7)	903.0	884.0	2,628.9	1,026.6
Deferred taxes (Note 8)	637.7	595.7	549.4	623.1
Regulatory liabilities, non-current (Note 4)	118.6	114.0	118.6	114.0
Pension, retiree and other benefits	47.5	64.9	47.5	64.9
Unamortized investment tax credit	29.9	32.4	3.6	32.4
Insurance and claims costs			14.2	10.1
Other deferred credits	163.9	147.2	205.6	146.2
Total noncurrent liabilities	1,900.6	1,838.2	3,567.8	2,017.3
Redeemable preferred stock	22.9	22.9	18.4	22.9
Commitments and contingencies (Note 14)
Common shareholders' equity:
Common stock, at par value of $0.01 per share:	0.4	0.4	0	1.2
Warrants			0	2.7
Common stock held by employee plans			0	(12.5)
Other paid-in capital	803.1	782.4	2,237.3	0
Accumulated other comprehensive loss	(34.7)	(20.2)	(0.4)	(18.9)
Retained earnings	589.1	616.9	(6.2)	1,246.0
Total common shareholders' equity	1,357.9	1,379.5	2,230.7	1,218.5
Total Liabilities and Shareholders' Equity	$ 3,525.7	$ 3,475.4	$ 6,107.5	$ 3,813.3