Debt Obligations (Long-term Debt Maturities) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Due within one year	$ 570.4
Due within two years	425.2
Due within three years	0.1
Due within four years	450.1
Due within five years	0.2
Thereafter	1,152.8
Total Maturities	2,598.8
Unamortized discounts and premiums, net	(6.3)
Total	2,605.1
DP&L [Member]
Due within one year	570.4
Due within two years	0.2
Due within three years	0.1
Due within four years	0.1
Due within five years	0.1
Thereafter	332.3
Total Maturities	903.2
Unamortized discounts and premiums, net	0.1	0.1
Total	$ 903.1