Summary of Significant Accounting Policies (Related Party Transactions) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
DP&L [Member]
Premiums paid for insurance services provided by MVIC	$ (2.9)		$ (2.6)		$ (3.1)
Expense recoveries for services provided to DPLER	5.2		4.0		4.6
Deposits received from DPLER	19.2		20.2
DPLE and DPLER [Member]
Sales to related party	345.8	[1]	350.8	[1]	327.0	[1]
MC Squared [Member]
Sales to related party	$ 108.1		$ 40.0

[1] DP&L sells power to DPLER and MC Squared to satisfy the electric requirements of their retail customers. The revenue dollars associated with sales to DPLER and MC Squared are recorded as wholesale revenues in DP&L’s Financial Statements. The increase in DP&L’s sales to DPLER during the year ended December 31, 2012, compared to the year ended December 31, 2011 is primarily due to customers electing to switch their generation service from DP&L to DPLER. DP&L started selling physical power to MC Squared during June 2012 and became their sole source of power in September 2012.