Derivative Instruments and Hedging Activities (Classification within the Condensed Consolidated Statements of Results of Operations or Balance Sheets of the Gains and Losses) (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Change in unrealized gain / (loss)	$ (1,800,000)	$ (5,900,000)
Gain (Loss) on Derivative Instruments, Net, Pretax	(2,600,000)	(1,900,000)
Derivative, Gain (Loss) on Derivative, Net	(4,400,000)	(7,800,000)
Commodity Contract - FTR [Member]
Change in unrealized gain / (loss)	900,000	(300,000)
Gain (Loss) on Derivative Instruments, Net, Pretax	(100,000)
Derivative, Gain (Loss) on Derivative, Net	800,000	(300,000)
Commodity Contract - Heating Oil [Member]
Change in unrealized gain / (loss)	100,000	(100,000)
Gain (Loss) on Derivative Instruments, Net, Pretax	(100,000)	100,000
Forward Contract Power [Member]
Change in unrealized gain / (loss)	(2,900,000)	(5,500,000)
Gain (Loss) on Derivative Instruments, Net, Pretax	(2,300,000)	(2,000,000)
Derivative, Gain (Loss) on Derivative, Net	(5,200,000)	(7,500,000)
Natural Gas [Member]
Change in unrealized gain / (loss)	100,000
Gain (Loss) on Derivative Instruments, Net, Pretax	(100,000)
DP&L [Member]
Change in unrealized gain / (loss)	(1,800,000)	(5,900,000)
Gain (Loss) on Derivative Instruments, Net, Pretax	(4,400,000)	(1,300,000)
Derivative, Gain (Loss) on Derivative, Net	(2,600,000)	(7,200,000)
DP&L [Member] | NYMEX Coal Contract [Member]
Change in unrealized gain / (loss)	100,000	(100,000)
Gain (Loss) on Derivative Instruments, Net, Pretax		100,000
Derivative, Gain (Loss) on Derivative, Net	(100,000)
DP&L [Member] | Commodity Contract - FTR [Member]
Change in unrealized gain / (loss)		(5,500,000)
Gain (Loss) on Derivative Instruments, Net, Pretax		(1,400,000)
Derivative, Gain (Loss) on Derivative, Net		(6,900,000)
DP&L [Member] | Commodity Contract - Heating Oil [Member]
Change in unrealized gain / (loss)	900,000	(300,000)
Gain (Loss) on Derivative Instruments, Net, Pretax	800,000
Derivative, Gain (Loss) on Derivative, Net	(100,000)	(300,000)
DP&L [Member] | Forward Contract Power [Member]
Change in unrealized gain / (loss)	(2,900,000)
Gain (Loss) on Derivative Instruments, Net, Pretax	(5,200,000)
Derivative, Gain (Loss) on Derivative, Net	(2,300,000)
DP&L [Member] | Natural Gas [Member]
Change in unrealized gain / (loss)	100,000
Derivative, Gain (Loss) on Derivative, Net	(100,000)
Revenue [Member]
Derivative, Gain (Loss) on Derivative, Net	(300,000)
Revenue [Member] | Forward Contract Power [Member]
Derivative, Gain (Loss) on Derivative, Net	(300,000)
Revenue [Member] | DP&L [Member]
Derivative, Gain (Loss) on Derivative, Net	(300,000)	800,000
Revenue [Member] | DP&L [Member] | Commodity Contract - FTR [Member]
Derivative, Gain (Loss) on Derivative, Net		800,000
Revenue [Member] | DP&L [Member] | Forward Contract Power [Member]
Derivative, Gain (Loss) on Derivative, Net	(300,000)
Purchased Power [Member]
Derivative, Gain (Loss) on Derivative, Net	(4,100,000)	(7,800,000)
Purchased Power [Member] | Commodity Contract - FTR [Member]
Derivative, Gain (Loss) on Derivative, Net	800,000	(300,000)
Purchased Power [Member] | Forward Contract Power [Member]
Derivative, Gain (Loss) on Derivative, Net	(4,900,000)	(7,500,000)
Purchased Power [Member] | DP&L [Member]
Derivative, Gain (Loss) on Derivative, Net	(4,100,000)	(8,000,000)
Purchased Power [Member] | DP&L [Member] | Commodity Contract - FTR [Member]
Derivative, Gain (Loss) on Derivative, Net		(7,700,000)
Purchased Power [Member] | DP&L [Member] | Commodity Contract - Heating Oil [Member]
Derivative, Gain (Loss) on Derivative, Net	800,000	(300,000)
Purchased Power [Member] | DP&L [Member] | Forward Contract Power [Member]
Derivative, Gain (Loss) on Derivative, Net	$ (4,900,000)