Summary of Significant Accounting Policies (Related Party Transactions) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
DP&L [Member]
Premiums paid for insurance services provided by MVIC	$ (0.7)	[1]	$ (0.6)	[1]
Expense recoveries for services provided to DPLER	1.1	[2]	0.9	[2]
Deposits received from DPLER	19.2	[3]
DPLE and DPLER [Member]
Sales to related party	78.7	[4]	83.0	[4]
MC Squared [Member]
Sales to related party	$ 25.6

[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 administrative 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 to satisfy the electric requirements of DPLER’s retail customers. The revenue dollars associated with sales to DPLER are recorded as wholesale revenues in DP&L’s Financial Statements. The decrease in DP&L’s sales to DPLER during the three months ended March 31, 2013, compared to the three months ended March 31, 2012, is primarily due to the transfer price for the current customer base being lower than the previous year’s transfer price. The increase in DP&L’s sales to MC Squared during the three months ended March 31, 2013, compared to the three months ended March 31, 2012, is a result of these sales beginning in September 2012.