Benefit Plans (Defined Benefits Plan Assets, Target Allocations) (Details)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Equity Securities [Member]
Target Allocation	38.00%
Percentage of plan assets	37.00%	17.00%
Debt Securities [Member]
Target Allocation	56.00%
Percentage of plan assets	53.00%	67.00%
Real Estate [Member]
Target Allocation	6.00%
Percentage of plan assets	10.00%	9.00%
Other Investments [Member]
Target Allocation	0.00%
Percentage of plan assets	0.00%	7.00%
THE DAYTON POWER AND LIGHT COMPANY [Member] | Equity Securities [Member]
Target Allocation	38.00%
Percentage of plan assets	37.00%	17.00%
THE DAYTON POWER AND LIGHT COMPANY [Member] | Debt Securities [Member]
Target Allocation	56.00%
Percentage of plan assets	53.00%	67.00%
THE DAYTON POWER AND LIGHT COMPANY [Member] | Real Estate [Member]
Target Allocation	6.00%
Percentage of plan assets	10.00%	9.00%
THE DAYTON POWER AND LIGHT COMPANY [Member] | Other Investments [Member]
Target Allocation	0.00%
Percentage of plan assets	0.00%	7.00%