Pension and Postretirement Benefits (Fair Value Measurements for Pension Plan Assets) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	$ 65.3
Total Debt Securities	236.8
Total Other Investments	46.1
Total Pension Plan Assets	349.1
DP&L [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	65.3	101.8
Total Debt Securities	236.8	208.7
Total Other Investments	46.1	37.0
Total Pension Plan Assets	349.1	361.4
Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities		101.8
Total Debt Securities		208.7
Total Other Investments		37.0
Total Pension Plan Assets	349.1	361.4	335.9
Pension [Member] | DP&L [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Other Investments		37.0
Total Pension Plan Assets	349.1	361.4	335.9
Level 1 [Member] | Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	65.3	101.8
Total Debt Securities	236.8	208.7
Total Pension Plan Assets	303.0	324.4
Level 1 [Member] | Pension [Member] | DP&L [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	65.3	101.8
Total Debt Securities	236.8	208.7
Total Pension Plan Assets	303.0	324.4
Level 2 [Member] | Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Other Investments	46.1	37.0
Total Pension Plan Assets	46.1	37.0
Level 2 [Member] | Pension [Member] | DP&L [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Other Investments	46.1	37.0
Total Pension Plan Assets	46.1	37.0
Small/Mid Cap Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	10.5
Small/Mid Cap Equity [Member] | DP&L [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	10.5	14.3
Small/Mid Cap Equity [Member] | Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities		14.3
Small/Mid Cap Equity [Member] | Level 1 [Member] | Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	10.5	14.3
Small/Mid Cap Equity [Member] | Level 1 [Member] | Pension [Member] | DP&L [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	10.5	14.3
Large Cap Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	20.8
Large Cap Equity [Member] | DP&L [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	20.8	50.5
Large Cap Equity [Member] | Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities		50.5
Large Cap Equity [Member] | Level 1 [Member] | Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	20.8	50.5
Large Cap Equity [Member] | Level 1 [Member] | Pension [Member] | DP&L [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	20.8	50.5
International Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	20.3
International Equity [Member] | DP&L [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	20.3	37.0
International Equity [Member] | Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities		37.0
International Equity [Member] | Level 1 [Member] | Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	20.3	37.0
International Equity [Member] | Level 1 [Member] | Pension [Member] | DP&L [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	20.3	37.0
Emerging markets equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	3.2
Emerging markets equity [Member] | DP&L [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	3.2
Emerging markets equity [Member] | Level 1 [Member] | Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	3.2
Emerging markets equity [Member] | Level 1 [Member] | Pension [Member] | DP&L [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	3.2
SIIT dynamic equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	10.5
SIIT dynamic equity [Member] | DP&L [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	10.5
SIIT dynamic equity [Member] | Level 1 [Member] | Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	10.5
SIIT dynamic equity [Member] | Level 1 [Member] | Pension [Member] | DP&L [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	10.5
Emerging Markets Debt [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Debt Securities	6.6
Emerging Markets Debt [Member] | DP&L [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Debt Securities	6.6	7.4
Emerging Markets Debt [Member] | Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Debt Securities		7.4
Emerging Markets Debt [Member] | Level 1 [Member] | Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Debt Securities	6.6	7.4
Emerging Markets Debt [Member] | Level 1 [Member] | Pension [Member] | DP&L [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Debt Securities	6.6	7.4
High Yield Bond [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Debt Securities	6.9
High Yield Bond [Member] | DP&L [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Debt Securities	6.9	12.7
High Yield Bond [Member] | Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Debt Securities		12.7
High Yield Bond [Member] | Level 1 [Member] | Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Debt Securities	6.9	12.7
High Yield Bond [Member] | Level 1 [Member] | Pension [Member] | DP&L [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Debt Securities	6.9	12.7
Long Duration Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Debt Securities	223.3
Long Duration Fund [Member] | DP&L [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Debt Securities	223.3	188.6
Long Duration Fund [Member] | Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Debt Securities		188.6
Long Duration Fund [Member] | Level 1 [Member] | Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Debt Securities	223.3	188.6
Long Duration Fund [Member] | Level 1 [Member] | Pension [Member] | DP&L [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Debt Securities	223.3	188.6
Cash [Member]
Defined Benefit Plan Disclosure [Line Items]
Cash	0.9
Cash [Member] | DP&L [Member]
Defined Benefit Plan Disclosure [Line Items]
Cash	0.9	13.9
Cash [Member] | Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Cash		13.9
Cash [Member] | Level 1 [Member] | Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Cash	0.9	13.9
Cash [Member] | Level 1 [Member] | Pension [Member] | DP&L [Member]
Defined Benefit Plan Disclosure [Line Items]
Cash	0.9	13.9
Limited Partnership Interest [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Other Investments	23.5
Limited Partnership Interest [Member] | Level 2 [Member] | Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Other Investments	23.5
Core Property Collective Fund [Member] | DP&L [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Other Investments	23.5
Core Property Collective Fund [Member] | Level 2 [Member] | Pension [Member] | DP&L [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Other Investments	23.5
Common Collective Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Other Investments	22.6
Common Collective Fund [Member] | DP&L [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Other Investments	22.6	37.0
Common Collective Fund [Member] | Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Other Investments		37.0
Common Collective Fund [Member] | Level 2 [Member] | Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Other Investments	22.6	37.0
Common Collective Fund [Member] | Level 2 [Member] | Pension [Member] | DP&L [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Other Investments	$ 22.6	$ 37.0