Income Taxes (Reconciliation of Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of year	$ 3.0	$ 8.8
Tax positions taken during prior periods	0.0	2.8
Lapse of applicable statute of limitations	0.0	(8.6)
Balance at end of year	3.0	3.0
THE DAYTON POWER AND LIGHT COMPANY [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of year	3.0	8.8
Tax positions taken during prior periods	0.0	2.8
Lapse of applicable statute of limitations	0.0	(8.6)
Tax positions taken during current period		0.0
Balance at end of year	$ 3.0	$ 3.0