Overview and Summary of Significant Accounting Policies (Related Party Transactions) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
DP&L [Member]
Premiums paid for insurance services provided by MVIC	$ (2.6)	[1]	$ (3.1)	[1]	$ (3.3)	[1]
Expense recoveries for services provided to DPLER	4.0	[2]	4.6	[2]	5.8	[2]
Deposits received from DPLER	20.2	[3]
DPLE and DPLER [Member]
Sales to related party	350.8	[4]	327.0	[4]	238.5	[4]
MC Squared [Member]
Sales to related party	$ 40.0

[1] MVIC, a wholly-owned captive insurance subsidiary of DPL, provides insurance coverage to DP&L and other DPL subsidiaries for workers’ compensation, general liability, property damages and directors’ and officers’ liability. These amounts represent insurance premiums paid by DP&L to MVIC.

[2] In the normal course of business DP&L incurs and records expenses on behalf of DPLER. Such expenses include but are not limited to employee-related expenses, accounting, information technology, payroll, legal and other administration expenses. DP&L subsequently charges these expenses to DPLER at DP&L’s cost and credits the expense in which they were initially recorded.

[3] DP&L requires credit assurance from the CRES providers serving customers in its service territory because DP&L is the default energy provider should the CRES provider fail to fulfill its obligations to provide electricity. Due to DPL’s credit downgrade, DP&L required cash collateral from DPLER.

[4] 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.