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	$ 2.4		$ (1.0)					$ 2.0
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
Net comprehensive income/ (loss)	72.5							88.7
Net loss	70.1		1.0					86.7
Common stock dividends								(43.8)		(43.8)
Stockholders' Equity Note, Spinoff Transaction
Proceeds from Contributions from Parent	0.0							(80.0)		80.0
Preferred stock dividends								(10.0)
Other	0.1		0.1					(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 | 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							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							41,172,173
Non-cash capital contribution			0.0
Disposal Group, Including Discontinued Operation, Net Assets															0.0
Other Comprehensive Income (Loss), Net of Tax	(8.7)						$ (0.9)	(5.2)						$ 0.4
Net comprehensive income/ (loss)	(9.7)							45.9
Net loss	(1.0)							51.1
Common stock dividends								(52.7)		(52.7)
Proceeds from Contributions from Parent	(98.0)		(98.0)					(150.0)		150.0
Other	0.1		0.1					0.1		0.1			0.0
Balance at Dec. 31, 2020	$ (283.5)	$ 0.0	2,468.8		$ (12.3)	$ (2,740.0)		$ 616.7	$ 0.4	$ 714.4		$ (42.1)	$ (56.0)
Balance (in shares) at Dec. 31, 2020		1
Non-cash capital contribution			$ 0.0
Disposal Group, Including Discontinued Operation, Net Assets															$ 0.0