Common Shareholders' Equity (Details) (USD $)	1 Months Ended		3 Months Ended					11 Months Ended	12 Months Ended				3 Months Ended							12 Months Ended
	Dec. 31, 2011	Jun. 30, 2011	Mar. 31, 2012	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Nov. 27, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2001	Dec. 31, 2012 DP&L [Member]	Sep. 30, 2012 DP&L [Member]	Jun. 30, 2012 DP&L [Member]	Mar. 31, 2012 DP&L [Member]	Dec. 31, 2010 DP&L [Member]	Jun. 30, 2010 DP&L [Member]	Mar. 31, 2010 DP&L [Member]	Dec. 31, 2012 DP&L [Member]	Dec. 31, 2011 DP&L [Member]
Common stock, shares authorized									1,500				250,000,000							250,000,000
Common stock, shares outstanding									1				41,172,173							41,172,173
Amount authorized to be repurchased											$ 200,000,000
Shares repurchase average per share price												$ 130
Warrants exercised		700,000	1,000,000
Proceeds from exercise of warrants		14,700,000
Warrants aggregate purchase price			9.00
Warrant Exercise Price			$ 21.00
Fixed rate									2.06%											2.06%
PUCO Meger Equity Ratio Approval									50.00%
ESOP amount of the loan used to purchase shares									90,000,000				90,000,000							90,000,000
Compensation expense associated with the ESOP	0							4,800,000		4,800,000	6,700,000
ESOP Loan Repayment To Employer	68,000,000									68,000,000											68,000,000
ESOP cumulative shares outstanding for calculation of EPS										4,600,000	4,200,000
Financial Instruments Subject to Mandatory Redemption, Settlement Terms, Excess of Liabilities over Assets	9,000,000									9,000,000
Acquisition cost per share										$ 30.00
Cash Dividends Paid to Parent Company				$ 0.3025	$ 0.3025	$ 0.3025	$ 0.3025						$ 40,000,000	$ 65,000,000	$ 45,000,000	$ 70,000,000	$ 150,000,000	$ 60,000,000	$ 90,000,000