Consolidated Statements of Shareholders' Equity (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Common stock, shares authorized	1,500	1,500
THE DAYTON POWER AND LIGHT COMPANY [Member]
Common stock, par value (in USD per share)	$ 0.01	$ 0.01
Common stock, shares authorized	250,000,000	250,000,000