Selected Quarterly Information (Unaudited) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	2 Months Ended	3 Months Ended			11 Months Ended	3 Months Ended
	Nov. 27, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Nov. 27, 2011	Dec. 31, 2011 DP&L [Member]	Sep. 30, 2011 DP&L [Member]	Jun. 30, 2011 DP&L [Member]	Mar. 31, 2011 DP&L [Member]
Revenues	$ 259.4	$ 497.5	$ 433.4	$ 480.6		$ 378.4	$ 452.5	$ 397.0	$ 449.8
Operating income	48.2	112.9	65.8	100.9		74.8	100.0	55.8	89.3
Net income	8.2	67.1	31.7	43.5		45.8	63.9	30.8	52.7
Basic	$ 0.07	$ 0.58	$ 0.28	$ 0.38	$ 1.31
Diluted	$ 0.07	$ 0.58	$ 0.28	$ 0.38	$ 1.31
Dividends declared and paid per share	$ 0.5400	$ 0.3325	$ 0.3325	$ 0.3325
Earnings on common stock						45.5	63.7	30.6	52.5
Dividends paid on common stock to parent						$ 40.0	$ 65.0	$ 45.0	$ 70.0