Derivative Instruments and Hedging Activities (Tables)

3 Months Ended

6 Months Ended

12 Months Ended

15 Months Ended

18 Months Ended

Jun. 30, 2013

Jun. 30, 2012

Jun. 30, 2013

Jun. 30, 2012

Dec. 31, 2012

Jun. 30, 2013

Jun. 30, 2013

Schedule of Notional Amounts of Outstanding Derivative Positions

Commodity	Accounting Treatment		Unit	Purchases (in thousands)		Sales (in thousands)		Net Purchases/ (Sales) (in thousands)
FTRs		Mark to Market	MWh		10.7		-		10.7
Heating oil futures		Mark to Market	Gallons		1,638.0		-		1,638.0
Forward power contracts		Cash Flow Hedge	MWh		421.6		(4,719.4)		(4,297.8)
Forward power contracts		Mark to Market	MWh		2,653.3		(7,012.5)		(4,359.2)

Commodity	Accounting Treatment		Unit	Purchases (in thousands)		Sales (in thousands)		Net Purchases/ (Sales) (in thousands)
FTRs		Mark to Market	MWh		6.9		-		6.9
Heating oil futures		Mark to Market	Gallons		1,764.0		-		1,764.0
Forward power contracts		Cash Flow Hedge	MWh		1,021.0		(2,197.9)		(1,176.9)
Forward power contracts		Mark to Market	MWh		2,510.7		(4,760.4)		(2,249.7)
Interest rate swaps		Cash Flow Hedge	USD	$	160,000.0	$	-	$	160,000.0

Gains or Losses Recognized in AOCI for the Cash Flow Hedges

	Three months ended				Three months ended
	September 30, 2013				September 30, 2012
			Interest				Interest
$ in millions (net of tax)	Power		Rate Hedge		Power		Rate Hedge
Beginning accumulated derivative gain / (loss) in AOCI	$	(1.1)	$	12.8	$	(2.4)	$	(4.7)
Net gains / (losses) associated with current period hedging transactions		(0.2)		6.4		(2.2)		2.5
Net gains / (losses) reclassified to earnings
Revenues		0.3		-		(0.1)		-
Purchased power		1.0		-		0.1		-
Ending accumulated derivative gain / (loss) in AOCI	$	-	$	19.2	$	(4.6)	$	(2.2)
Net gains / (losses) associated with the ineffective portion of the hedging transaction are presented in the following lines of the Condensed Consolidated Statements of Results of Operations:
Interest expense	$	-	$	(0.5)	$	-	$	-
Portion expected to be reclassified to earnings in the next twelve months (a)	$	(2.9)	$	(1.0)
Maximum length of time that we are hedging our exposure to variability in future cash flows related to forecasted transactions (in months)		39		0

Schedule of Other Derivatives Not Designated as Hedging Instruments, Statements of Financial Performance and Financial Position, Location

For the three months ended September 30, 2013
$ in millions	Heating Oil		FTRs		Power		Total
Change in unrealized gain	$	0.1	$	1.3	$	0.1	$	1.5
Realized gain / (loss)		0.1		-		(0.8)		(0.7)
Total	$	0.2	$	1.3	$	(0.7)	$	0.8
Recorded in Income Statement:  gain / (loss)
Revenues	$	-	$	-	$	-	$	-
Purchased power		-		1.3		(0.7)		0.6
Fuel		0.1		-		-		0.1
O&M		0.1		-		-		0.1
Total	$	0.2	$	1.3	$	(0.7)	$	0.8

For the three months ended September 30, 2012
	NYMEX
$ in millions	Coal		Heating Oil		FTRs		Power		Total
Change in unrealized gain / (loss)	$	15.5	$	-	$	0.1	$	(2.9)	$	12.7
Realized gain / (loss)		(12.8)		0.5		0.1		0.1		(12.1)
Total	$	2.7	$	0.5	$	0.2	$	(2.8)	$	0.6
Recorded on Balance Sheet:
Partners' share of gain / (loss)	$	4.7	$	-	$	-	$	-	$	4.7
Regulatory (asset) / liability		1.2		(0.1)		-		-		1.1
Recorded in Income Statement:  gain / (loss)
Revenues		-		-		-		(2.4)		(2.4)
Purchased power		-		-		0.2		(0.4)		(0.2)
Fuel		(3.2)		0.5		-		-		(2.7)
O&M		-		0.1		-		-		0.1
Total	$	2.7	$	0.5	$	0.2	$	(2.8)	$	0.6

For the nine months ended September 30, 2013
$ in millions	Heating Oil		FTRs		Power		Total
Change in unrealized gain / (loss)	$	(0.2)	$	0.4	$	10.5	$	10.7
Realized gain / (loss)		-		1.2		0.5		1.7
Total	$	(0.2)	$	1.6	$	11.0	$	12.4
Recorded on Balance Sheet:
Regulatory (asset) / liability	$	(0.1)	$	-	$	-	$	(0.1)
Recorded in Income Statement:  gain / (loss)
Purchased power		-		1.6		11.0		12.6
Fuel		(0.1)		-		-		(0.1)
O&M		-		-		-		-
Total	$	(0.2)	$	1.6	$	11.0	$	12.4

For the nine months ended September 30, 2012
	NYMEX
$ in millions	Coal		Heating Oil		FTRs		Power		Total
Change in unrealized gain / (loss)	$	13.4	$	(1.5)	$	(0.1)	$	(0.6)	$	11.2
Realized gain / (loss)		(27.2)		1.9		0.5		(4.2)		(29.0)
Total	$	(13.8)	$	0.4	$	0.4	$	(4.8)	$	(17.8)
Recorded on Balance Sheet:
Partners' share of gain / (loss)	$	3.5	$	-	$	-	$	-	$	3.5
Regulatory (asset) / liability		0.9		(0.6)		-		-		0.3
Recorded in Income Statement:  gain / (loss)
Revenues		-		-		-		(1.7)		(1.7)
Purchased power		-		-		0.4		(3.1)		(2.7)
Fuel		(18.2)		0.8		-		-		(17.4)
O&M		-		0.2		-		-		0.2
Total	$	(13.8)	$	0.4	$	0.4	$	(4.8)	$	(17.8)

Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block]

Fair Values of Derivative Instruments
at September 30, 2013
				Gross Amounts Not Offset in the Condensed Consolidated Balance Sheets
$ in millions	Hedging Designation	Gross Fair Value as presented in the Condensed Consolidated Balance Sheets		Financial Instruments with Same Counterparty in Offsetting Position		Cash Collateral		Net Amount
Assets
Short-term derivative positions (presented in Other current assets)
Forward power contracts	Cash Flow	$	1.4	$	(1.1)	$	-	$	0.3
Forward power contracts	MTM		5.1		(2.6)		-		2.5
Heating oil	MTM		0.1		-		-		0.1
FTRs	MTM		0.4		-		-		0.4
Long-term derivative positions (presented in Other deferred assets)
Forward power contracts	Cash Flow		1.9		(0.5)		-		1.4
Forward power contracts	MTM		12.7		(0.7)		-		12.0
Total assets		$	21.6	$	(4.9)	$	-	$	16.7
Liabilities
Short-term derivative positions (presented in Other current liabilities)
Forward power contracts	Cash Flow	$	3.7	$	(1.1)	$	(2.3)	$	0.3
Forward power contracts	MTM		5.0		(2.6)		(2.1)		0.3
Long-term derivative positions (presented in Other deferred liabilities)
Forward power contracts	Cash Flow		0.5		(0.5)		-		-
Forward power contracts	MTM		1.1		(0.7)		-		0.4
Total liabilities		$	10.3	$	(4.9)	$	(4.4)	$	1.0

Fair Values of Derivative Instruments Not Designated as Hedging Instruments
at December 31, 2012
				Gross Amounts Not Offset in the Condensed Consolidated Balance Sheets
$ in millions	Hedging Designation	Gross Fair Value as presented in the Condensed Consolidated Balance Sheets		Financial Instruments with Same Counterparty in Offsetting Position		Cash Collateral		Net Amount
Assets
Short-term derivative positions (presented in Other current assets)
Forward power contracts	Cash Flow	$	0.5	$	(0.5)	$	-	$	-
Forward power contracts	MTM		2.7		(1.5)		-		1.2
Heating oil futures	MTM		0.2		-		(0.2)		-
Long-term derivative positions (presented in Other deferred assets)
Forward power contracts	Cash Flow		0.5		(0.5)		-		-
Forward power contracts	MTM		3.6		(0.6)		-		3.0
Total assets		$	7.5	$	(3.1)	$	(0.2)	$	4.2
Liabilities
Short-term derivative positions (presented in Other current liabilities)
Forward power contracts	Cash Flow	$	6.7	$	(0.5)	$	(2.1)	$	4.1
Interest rate hedge	Cash Flow		29.5		-		-		29.5
FTRs	MTM		0.1		-		-		0.1
Forward power contracts	MTM		4.1		(1.5)		(2.0)		0.6
Long-term derivative positions (presented in Other deferred liabilities)
Forward power contracts	Cash Flow		1.5		(0.5)		(0.9)		0.1
Forward power contracts	MTM		0.8		(0.6)		(0.1)		0.1
Total liabilities		$	42.7	$	(3.1)	$	(5.1)	$	34.5

DP&L [Member]

Schedule of Notional Amounts of Outstanding Derivative Positions

Commodity	Accounting Treatment		Unit	Purchases (in thousands)		Sales (in thousands)		Net Purchases/ (Sales) (in thousands)
FTRs		Mark to Market	MWh		10.7		-		10.7
Heating oil futures		Mark to Market	Gallons		1,638.0		-		1,638.0
Forward power contracts		Cash Flow Hedge	MWh		421.6		(4,719.4)		(4,297.8)
Forward power contracts		Mark to Market	MWh		2,624.6		(7,041.3)		(4,416.7)

Commodity	Accounting Treatment		Unit	Purchases (in thousands)		Sales (in thousands)		Net Purchases/ (Sales) (in thousands)
FTRs		Mark to Market	MWh		6.9		-		6.9
Heating oil futures		Mark to Market	Gallons		1,764.0		-		1,764.0
Forward power contracts		Cash Flow Hedge	MWh		1,021.0		(2,197.9)		(1,176.9)
Forward power contracts		Mark to Market	MWh		2,296.6		(4,760.4)		(2,463.8)

Gains or Losses Recognized in AOCI for the Cash Flow Hedges

	Three months ended				Three months ended
	September 30, 2013				September 30, 2012
			Interest				Interest
$ in millions (net of tax)	Power		Rate Hedge		Power		Rate Hedge
Beginning accumulated derivative gain / (loss) in AOCI	$	(1.9)	$	6.1	$	(3.4)	$	8.6
Net gains / (losses) associated with current period hedging transactions		(0.3)		-		(2.5)		(0.6)
Net gains / (losses) reclassified to earnings
Interest expense		-		(0.6)		-		-
Revenues		0.3		-		-		-
Purchased power		1.3		-		(0.1)		-
Ending accumulated derivative gain / (loss) in AOCI	$	(0.6)	$	5.5	$	(6.0)	$	8.0
Portion expected to be reclassified to earnings in the next twelve months (a)	$	(2.3)	$	(2.4)
Maximum length of time that we are hedging our exposure to variability in future cash flows related to forecasted transactions (in months)		39		-

	Nine months ended				Nine months ended
	September 30, 2013				September 30, 2012
			Interest				Interest
$ in millions (net of tax)	Power		Rate Hedge		Power		Rate Hedge
Beginning accumulated derivative gain / (loss) in AOCI	$	(4.7)	$	7.3	$	(0.7)	$	9.8
Net gains / (losses) associated with current period hedging transactions		-		-		(4.0)		-
Net gains / (losses) reclassified to earnings
Interest expense		-		(1.8)		-		(1.8)
Revenues		1.4		-		0.1		-
Purchased power		2.7		-		(1.4)		-
Ending accumulated derivative gain / (loss) in AOCI	$	(0.6)	$	5.5	$	(6.0)	$	8.0
Portion expected to be reclassified to earnings in the next twelve months (a)	$	(2.3)	$	(2.4)
Maximum length of time that we are hedging our exposure to variability in future cash flows related to forecasted transactions (in months)		39		-

Schedule of Other Derivatives Not Designated as Hedging Instruments, Statements of Financial Performance and Financial Position, Location

For the three months ended September 30, 2013
$ in millions	Heating Oil		FTRs		Power		Total
Change in unrealized gain / (loss)	$	0.1	$	1.3	$	(0.1)	$	1.3
Realized gain / (loss)		0.1		-		(0.8)		(0.7)
Total	$	0.2	$	1.3	$	(0.9)	$	0.6
Recorded in Income Statement: gain / (loss)
Revenues	$	-	$	-	$	0.1	$	0.1
Purchased power		-		1.3		(1.0)		0.3
Fuel		0.1		-		-		0.1
O&M		0.1		-		-		0.1
Total	$	0.2	$	1.3	$	(0.9)	$	0.6

For the three months ended September 30, 2012
	NYMEX
$ in millions	Coal		Heating Oil		FTRs		Power		Total
Change in unrealized gain / (loss)	$	15.5	$	-	$	0.1	$	(5.5)	$	10.1
Realized gain / (loss)		(12.8)		0.5		0.1		4.2		(8.0)
Total	$	2.7	$	0.5	$	0.2	$	(1.3)	$	2.1
Recorded on Balance Sheet:
Partners' share of gain / (loss)	$	4.7	$	-	$	-	$	-	$	4.7
Regulatory (asset) / liability		1.2		(0.1)		-		-		1.1
Recorded in Income Statement: gain / (loss)
Revenues		-		-		-		0.3		0.3
Purchased power		-		-		0.2		(1.6)		(1.4)
Fuel		(3.2)		0.5		-		-		(2.7)
O&M		-		0.1		-		-		0.1
Total	$	2.7	$	0.5	$	0.2	$	(1.3)	$	2.1

For the nine months ended September 30, 2013
$ in millions	Heating Oil		FTRs		Power		Total
Change in unrealized gain / (loss)	$	(0.2)	$	0.4	$	8.9	$	9.1
Realized gain / (loss)		-		1.2		1.1		2.3
Total	$	(0.2)	$	1.6	$	10.0	$	11.4
Recorded on Balance Sheet:
Regulatory (asset) / liability	$	(0.1)	$	-	$	-	$	(0.1)
Recorded in Income Statement: gain / (loss)
Revenues		-		-		0.2		0.2
Purchased power		-		1.6		9.8		11.4
Fuel		(0.1)		-		-		(0.1)
O&M		-		-		-		-
Total	$	(0.2)	$	1.6	$	10.0	$	11.4

For the nine months ended September 30, 2012
	NYMEX
$ in millions	Coal		Heating Oil		FTRs		Power		Total
Change in unrealized gain / (loss)	$	13.4	$	(1.5)	$	(0.1)	$	(4.6)	$	7.2
Realized gain / (loss)		(27.2)		1.9		0.5		4.2		(20.6)
Total	$	(13.8)	$	0.4	$	0.4	$	(0.4)	$	(13.4)
Recorded on Balance Sheet:
Partners' share of gain / (loss)	$	3.5	$	-	$	-	$	-	$	3.5
Regulatory (asset) / liability		0.9		(0.6)		-		-		0.3
Recorded in Income Statement: gain / (loss)
Revenues		-		-		-		2.0		2.0
Purchased power		-		-		0.4		(2.4)		(2.0)
Fuel		(18.2)		0.8		-		-		(17.4)
O&M		-		0.2		-		-		0.2
Total	$	(13.8)	$	0.4	$	0.4	$	(0.4)	$	(13.4)

Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block]

Fair Values of Derivative Instruments
at September 30, 2013
				Gross Amounts Not Offset in the Condensed Balance Sheets
$ in millions	Hedging Designation	Gross Fair Value as presented in the Condensed Balance Sheets		Financial Instruments with Same Counterparty in Offsetting Position		Cash Collateral		Net Amount
Assets
Short-term derivative positions (presented in Other current assets)
Forward power contracts	Cash Flow	$	1.4	$	(1.1)	$	-	$	0.3
Forward power contracts	MTM		5.2		(2.6)		-		2.6
Heating oil futures	MTM		0.1		-		-		0.1
FTRs	MTM		0.4		-		-		0.4
Long-term derivative positions (presented in Other deferred assets)
Forward power contracts	Cash Flow		1.9		(0.5)		-		1.4
Forward power contracts	MTM		12.7		(0.7)		-		12.0
Total assets		$	21.7	$	(4.9)	$	-	$	16.8
Liabilities
Short-term derivative positions (presented in Other current liabilities)
Forward power contracts	Cash Flow	$	3.8	$	(1.1)	$	(2.3)	$	0.4
Forward power contracts	MTM		4.7		(2.6)		(1.8)		0.3
Long-term derivative positions (presented in Other deferred liabilities)
Forward power contracts	Cash Flow		0.5		(0.5)		-		-
Forward power contracts	MTM		1.1		(0.7)		(0.1)		0.3
Total liabilities		$	10.1	$	(4.9)	$	(4.2)	$	1.0

Fair Values of Derivative Instruments
at December 31, 2012
				Gross Amounts Not Offset in the Condensed Balance Sheets
$ in millions	Hedging Designation	Gross Fair Value as presented in the Condensed Balance Sheets		Financial Instruments with Same Counterparty in Offsetting Position		Cash Collateral		Net Amount
Assets
Short-term derivative positions (presented in Other current assets)
Forward power contracts	Cash Flow	$	0.5	$	(0.5)	$	-	$	-
Forward power contracts	MTM		2.8		(1.5)		-		1.3
Heating oil futures	MTM		0.2		-		(0.2)		-
Long-term derivative positions (presented in Other deferred assets)
Forward power contracts	Cash Flow		0.5		(0.5)		-		-
Forward power contracts	MTM		3.6		(0.6)		-		3.0
Total assets		$	7.6	$	(3.1)	$	(0.2)	$	4.3
Liabilities
Short-term derivative positions (presented in Other current liabilities)
Forward power contracts	Cash Flow	$	6.7	$	(0.5)	$	(2.1)	$	4.1
FTRs	MTM		0.1		-		-		0.1
Forward power contracts	MTM		2.7		(1.5)		(0.5)		0.7
Long-term derivative positions (presented in Other deferred liabilities)
Forward power contracts	Cash Flow		1.5		(0.5)		(0.9)		0.1
Forward power contracts	MTM		0.7		(0.6)		-		0.1
Total liabilities		$	11.7	$	(3.1)	$	(3.5)	$	5.1