Consolidated Statements of Shareholders' Equity - USD ($) $ in Millions	Total	Common Stock [Member]	Other Paid-In Capital [Member]	Accumulated Other Comprehensive Income/(Loss) [Member]	Retained Earnings [Member]	THE DAYTON POWER AND LIGHT COMPANY [Member]	THE DAYTON POWER AND LIGHT COMPANY [Member] Common Stock [Member]	THE DAYTON POWER AND LIGHT COMPANY [Member] Other Paid-In Capital [Member]	THE DAYTON POWER AND LIGHT COMPANY [Member] Accumulated Other Comprehensive Income/(Loss) [Member]	THE DAYTON POWER AND LIGHT COMPANY [Member] Retained Earnings [Member]
Other Comprehensive Income (Loss), Net of Tax	$ 9.9					$ 13.6
Balance at Dec. 31, 2014	148.2	$ 0.0	$ 2,237.4	$ 7.5	$ (2,096.7)	1,143.4	$ 0.4	$ 803.5	$ (42.3)	$ 381.8
Balance (in shares) at Dec. 31, 2014		1					41,172,173
Net comprehensive income/ (loss)	(229.1)					120.0
Net loss	(239.0)					106.4
Common stock dividends						(50.0)				(50.0)
Proceeds from Contributions from Parent						0.0
Preferred stock dividends						(0.9)				(0.9)
Other	0.3		0.3			0.2		0.2
Balance at Dec. 31, 2015	(80.6)	$ 0.0	2,237.7	17.4	(2,335.7)	1,212.7	$ 0.4	803.7	(28.7)	437.3
Balance (in shares) at Dec. 31, 2015		1					41,172,173
Non-cash capital contribution	0.0
Other Comprehensive Income (Loss), Net of Tax	(17.1)					(13.8)
Preferred Stock Redemption Premium	5.1
Net comprehensive income/ (loss)	(502.3)					(786.5)
Net loss	(485.2)					(772.7)
Common stock dividends						70.0				(70.0)
Proceeds from Contributions from Parent						0.0
Preferred stock dividends						(0.7)				(0.7)
Other	(4.7)		(4.7)			6.8		7.0		(0.2)
Balance at Dec. 31, 2016	(587.6)	$ 0.0	2,233.0	0.3	(2,820.9)	362.3	$ 0.4	810.7	(42.5)	(406.3)
Balance (in shares) at Dec. 31, 2016		1					41,172,173
Non-cash capital contribution	0.0
Other Comprehensive Income (Loss), Net of Tax	0.5					8.4
Net comprehensive income/ (loss)	(94.1)					25.4
Net loss	(94.6)					17.0
Common stock dividends						(39.0)		(39.0)
Stockholders' Equity Note, Spinoff Transaction						(88.3)
Proceeds from Contributions from Parent						70.0		(70.0)
Other	97.4		97.4			0.3		(69.7)		70.0
Balance at Dec. 31, 2017	(584.3)	$ 0.0	$ 2,330.4	$ 0.8	$ (2,915.5)	$ 330.7	$ 0.4	$ 685.8	$ (36.2)	$ (319.3)
Balance (in shares) at Dec. 31, 2017		1
Non-cash capital contribution	$ 97.1