Consolidated Statements of Comprehensive Income/(Loss) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net loss	$ (94.6)	$ (485.2)	$ (239.0)
Available-for-sale securities activity:
Change in fair value of available-for-sale securities, net of income tax benefit/(expense)	0.5	0.2	(0.1)
Reclassification to earnings of available-for-sale securities, net of income tax expense/(benefit)	(0.1)	0.0	0.0
Total change in fair value of available-for-sale securities	0.4	0.2	(0.1)
Derivative activity:
Change in derivative fair value, net of income tax benefit/(expense)	9.6	16.1	18.2
Reclassification of earnings, net of income tax benefit/(expense)	(8.0)	(29.7)	(10.0)
Total change in fair value of derivatives	1.6	(13.6)	8.2
Pension and postretirement activity:
Prior service cost for the period, net of income tax benefit/(expense)	(0.7)	0.0	0.0
Net loss for the period, net of income tax benefit/(expense)	(1.8)	(4.7)	1.6
Reclassification to earnings, net of income tax benefit/(expense)	1.0	1.0	0.2
Total change in unfunded pension obligation	(1.5)	(3.7)	1.8
Other comprehensive income / (loss)	0.5	(17.1)	9.9
Net comprehensive income / (loss)	(94.1)	(502.3)	(229.1)
THE DAYTON POWER AND LIGHT COMPANY [Member]
Net loss	17.0	(772.7)	106.4
Available-for-sale securities activity:
Change in fair value of available-for-sale securities, net of income tax benefit/(expense)	0.5	0.2	(0.2)
Reclassification to earnings of available-for-sale securities, net of income tax expense/(benefit)	(0.1)	0.0	0.0
Total change in fair value of available-for-sale securities	0.4	0.2	(0.2)
Derivative activity:
Change in derivative fair value, net of income tax benefit/(expense)	12.4	16.1	18.2
Reclassification of earnings, net of income tax benefit/(expense)	(6.2)	(30.0)	(9.8)
Total change in fair value of derivatives	6.2	(13.9)	8.4
Pension and postretirement activity:
Prior service cost for the period, net of income tax benefit/(expense)	(1.9)	(0.1)	0.0
Net loss for the period, net of income tax benefit/(expense)	(0.8)	(5.9)	1.7
Reclassification to earnings, net of income tax benefit/(expense)	4.5	5.9	3.7
Total change in unfunded pension obligation	1.8	(0.1)	5.4
Other comprehensive income / (loss)	8.4	(13.8)	13.6
Net comprehensive income / (loss)	$ 25.4	$ (786.5)	$ 120.0