Consolidated Statements of Shareholders' Equity - USD ($) $ in Millions	Total	Common Stock [Member]	Other Paid-In Capital [Member]	Reclassification out of Accumulated Other Comprehensive Income [Member]	Accumulated Other Comprehensive Income/(Loss) [Member]	Retained Earnings [Member]	Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [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] Reclassification out of Accumulated Other Comprehensive Income [Member]	THE DAYTON POWER AND LIGHT COMPANY [Member] Accumulated Other Comprehensive Income/(Loss) [Member]	THE DAYTON POWER AND LIGHT COMPANY [Member] Retained Earnings [Member]	THE DAYTON POWER AND LIGHT COMPANY [Member] Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]	Generation [Member] THE DAYTON POWER AND LIGHT COMPANY [Member]
Other Comprehensive Income (Loss), Net of Tax	$ 0.5							$ 8.4
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
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														$ (2.1)
Proceeds from Contributions from Parent								(70.0)		70.0
Preferred stock dividends								(88.3)
Other	0.3		0.3					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							41,172,173
Non-cash capital contribution	97.1		97.1
Disposal Group, Including Discontinued Operation, Net Assets															$ (86.2)
Other Comprehensive Income (Loss), Net of Tax	2.4						$ 2.3	2.0						(0.8)
Net comprehensive income/ (loss)	72.5							88.7
Net loss	70.1							86.7
Common stock dividends								43.8		(43.8)
Proceeds from Contributions from Parent								(80.0)		80.0
Preferred stock dividends								(10.0)
Other	0.1		0.1	$ 1.0		1.0		(0.3)		(0.2)	$ (1.1)		1.0
Balance at Dec. 31, 2018	(471.7)	$ 0.0	2,370.5		2.2	(2,844.4)		445.3	$ 0.4	711.8		(35.3)	(231.6)
Balance (in shares) at Dec. 31, 2018		1							41,172,173
Non-cash capital contribution	40.0		40.0
AOCI reclassed to Retained Earnings before tax | Adjustments for New Accounting Pronouncement [Member]	1.6
AOCI reclassed to Retained Earnings, net of tax	(1.0)						0.0	(1.1)						0.0
AOCI reclassed to Retained Earnings, net of tax | Adjustments for New Accounting Pronouncement [Member]	1.0
Disposal Group, Including Discontinued Operation, Net Assets															(10.0)
Other Comprehensive Income (Loss), Net of Tax	(5.8)						$ (2.5)	(1.6)						$ (1.0)
Net comprehensive income/ (loss)	99.6							123.3
Net loss	105.4							124.9
Common stock dividends								(95.0)		(95.0)
Proceeds from Contributions from Parent								0.0
Other	0.2		0.2					(0.2)		0.2			(0.4)
Balance at Dec. 31, 2019	(371.9)	$ 0.0	2,370.7		$ (3.6)	$ (2,739.0)		$ 473.4	$ 0.4	$ 617.0		$ (36.9)	$ (107.1)
Balance (in shares) at Dec. 31, 2019		1
Non-cash capital contribution			$ 0.0
AOCI reclassed to Retained Earnings, net of tax | Adjustments for New Accounting Pronouncement [Member]	$ 1.0
Disposal Group, Including Discontinued Operation, Net Assets															$ 0.0