Consolidated Statements of Results of Operations (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Revenues	$ 394.6	$ 434.0
Cost of revenues:
Fuel	88.6	97.4
Purchased power	95.3	94.8
Amortization of intangibles	1.8	27.8
Total cost of revenues	185.7	220.0
Gross margin	208.9	214.0
Operating expenses:
Operation and maintenance	99.2	101.7
Depreciation and amortization	31.8	31.4
General taxes	21.0	21.7
Total operating expenses	152.0	154.8
Operating income	56.9	59.2
Other income / (expense), net:
Investment income	0.1	0.1
Interest expense	(30.5)	(29.6)
Other expense	(0.6)	(0.3)
Total other income / (expense), net	(31.0)	(29.8)
Earnings before income tax	25.9	29.4
Income tax expense	6.0	7.7
Net income	19.9	21.7
THE DAYTON POWER AND LIGHT COMPANY [Member]
Revenues	376.5	399.6
Cost of revenues:
Fuel	88.1	95.6
Purchased power	94.1	84.9
Total cost of revenues	182.2	180.5
Gross margin	194.3	219.1
Operating expenses:
Operation and maintenance	91.3	99.2
Depreciation and amortization	33.6	34.7
General taxes	19.8	20.2
Total operating expenses	144.7	154.1
Operating income	49.6	65.0
Other income / (expense), net:
Investment income	0.1	0.1
Interest expense	(9.3)	(9.6)
Other expense	(0.6)	(0.1)
Total other income / (expense), net	(9.8)	(9.6)
Earnings before income tax	39.8	55.4
Income tax expense	9.6	17.3
Net income	30.2	38.1
Dividends on preferred stock	0.2	0.2
Earnings on common stock	$ 30.0	$ 37.9