Consolidated Statements of Results of Operations (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Other income / (expense), net:
Earnings on common stock		$ 31.7		$ 75.2
Average number of common shares outstanding (millions):
Basic		114.2		114.1
Diluted		114.9		114.7
Earnings per share of common stock:
Basic		$ 0.28		$ 0.66
Diluted		$ 0.28		$ 0.66
THE DAYTON POWER AND LIGHT COMPANY [Member]
Revenues	346.6	396.9	746.2	846.7
Cost of revenues:
Fuel	68.6	89.1	164.2	187.7
Purchased power	69.3	104.4	154.2	222.2
Total cost of revenues	137.9	193.5	318.4	409.9
Gross margin	208.7	203.4	427.8	436.8
Operating expenses:
Operation and maintenance	96.0	95.1	195.2	186.5
Depreciation and amortization	36.1	33.4	70.8	66.5
General taxes	19.6	19.1	39.8	38.7
Total operating expenses	151.7	147.6	305.8	291.7
Operating income	57.0	55.8	122.0	145.1
Other income / (expense), net:
Investment income	0.1	0.5	0.2	1.1
Interest expense	(9.4)	(9.7)	(19.0)	(19.4)
Other expense	(0.8)	(0.3)	(0.9)	(0.8)
Total other income / (expense), net	(10.1)	(9.5)	(19.7)	(19.1)
Earnings before income tax	46.9	46.3	102.3	126.0
Income tax expense	15.6	15.5	32.9	42.5
Net income	31.3	30.8	69.4	83.5
Dividends on preferred stock	0.2	0.2	0.4	0.4
Earnings on common stock	31.1	30.6	69.0	83.1
Successor [Member]
Revenues	382.0		816.0
Cost of revenues:
Fuel	71.6		169.0
Purchased power	80.3		175.1
Amortization of intangibles	28.6		56.4
Total cost of revenues	180.5		400.5
Gross margin	201.5		415.5
Operating expenses:
Operation and maintenance	103.8		205.5
Depreciation and amortization	29.7		61.1
General taxes	21.3		43.0
Total operating expenses	154.8		309.6
Operating income	46.7		105.9
Other income / (expense), net:
Investment income	0.2		0.3
Interest expense	(32.4)		(62.0)
Charge for early redemption of debt
Other expense	(0.9)		(1.2)
Total other income / (expense), net	(33.1)		(62.9)
Earnings before income tax	13.6		43.0
Income tax expense	8.7		16.4
Net income	4.9		26.6
Predecessor [Member]
Revenues		433.3		913.9
Cost of revenues:
Fuel		92.1		191.9
Purchased power		113.6		234.4
Amortization of intangibles		0		0
Total cost of revenues		205.7		426.3
Gross margin		227.6		487.6
Operating expenses:
Operation and maintenance		106.8		206.2
Depreciation and amortization		35.1		70.2
General taxes		19.9		44.6
Total operating expenses		161.8		321.0
Operating income		65.8		166.6
Other income / (expense), net:
Investment income		0.1		0.2
Interest expense		(17.6)		(34.5)
Charge for early redemption of debt				(15.3)
Other expense		(0.3)		(0.7)
Total other income / (expense), net		(17.8)		(50.3)
Earnings before income tax		48.0		116.3
Income tax expense		16.3		41.1
Net income		$ 31.7		$ 75.2
Average number of common shares outstanding (millions):
Basic		114.2		114.1
Diluted		114.9		114.7
Earnings per share of common stock:
Basic		$ 0.28		$ 0.66
Diluted		$ 0.28		$ 0.66
Dividends paid per share of common stock		$ 0.3325		$ 0.665