Debt Obligations (Long-term Debt Maturities) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Due within one year	$ 480.3
Due within two years	40.1
Due within three years	485.1
Due within four years	490.1
Due within five years	70.1
Thereafter	1,252.8
Total Maturities	2,818.5
Unamortized discounts and premiums, net	4.0
Total	2,814.5
DP&L [Member]
Due within one year	470.3
Due within two years	0.1
Due within three years	445.1
Due within four years	0.1
Due within five years	0.1
Thereafter	431.5
Total Maturities	1,347.2
Unamortized discounts and premiums, net	$ 0.8	$ 0.1