Condensed Consolidated Balance Sheets (Parenthetical) (USD $)	Sep. 30, 2011	Dec. 31, 2010
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	250,000,000	250,000,000
Common stock, shares issued	163,724,211	163,724,211
Common stock, shares outstanding	117,724,111	116,924,844
THE DAYTON POWER AND LIGHT COMPANY [Member]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01