Summary of Significant Accounting Policies (Related Party Transactions) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2014	Mar. 31, 2013
Personnel costs paid to the Service Company	$ 13.2
Advances and Prepaids to the Service Company	5.4
Payables to the Service Company	13.2
DP&L [Member]
Premiums paid for insurance services provided by MVIC	(0.8)	(0.7)
Expense recoveries for services provided to DPLER		1.1
Deposits received from DPLER	19.2	19.2
Advances and Prepaids to the Service Company	5.4
DPLE and DPLER [Member]
Sales to related party	107.8	78.7
MC Squared [Member]
Sales to related party	31.0	25.6
Service Company [Member]
Personnel costs paid to the Service Company	11.4
Payables to the Service Company	$ 11.4

Amount for accounts payable to related parties. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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Amount of receivables arising from transactions with related parties due within one year or the normal operating cycle, if longer.

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- Definition

Amount of revenue, fees and commissions earned from transactions between (a) a parent company and its subsidiaries; (b) subsidiaries of a common parent; (c) an entity and trusts for the benefit of employees, for example, but not limited to, pension and profit-sharing trusts that are managed by or under the trusteeship of the entity's management; (d) an entity and its principal, owners, management, or members of their immediate families; and (e) affiliates.

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