Statement of Equity Statement - USD ($) $ in Millions	Total	Common Stock [Member]	Other Additional Capital [Member]		AOCI Attributable to Parent [Member]	Retained Earnings [Member]	Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]	Subsidiaries [Member]	Subsidiaries [Member] Common Stock [Member]	Subsidiaries [Member] Other Additional Capital [Member]	Subsidiaries [Member] AOCI Attributable to Parent [Member]	Subsidiaries [Member] Retained Earnings [Member]	Subsidiaries [Member] Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Shares, Issued		1							41,172,173
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Beginning 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)
Other Comprehensive Income (Loss), Net of Tax	(0.4)							0.4
Net income/ (loss)	42.1
Net Income (Loss) Attributable to Parent								29.0
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	41.7							29.4
Non-cash capital contribution	1.5		1.5	[1]
Stockholders' Equity, Other	0.1		(0.1)					(0.3)				0.3
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance at Mar. 31, 2019	(428.4)	0.0	2,372.1		1.8	(2,802.3)		474.4	0.4	711.8	(34.9)	(202.9)
Dividends, Common Stock, Cash										(90.0)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Beginning 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)
Other Comprehensive Income (Loss), Net of Tax	(2.2)							1.1
Net income/ (loss)	61.4							103.7
Proceeds from Contributions from Parent	0.0							0.0
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	59.2							104.8
Non-cash capital contribution	2.7
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance at Sep. 30, 2019	(409.6)	$ 0.0	2,373.4		0.0	(2,783.0)		459.8	$ 0.4	621.9	(34.2)	(128.3)
Shares, Issued		1							41,172,173
Dividends, Common Stock, Cash								(70.0)		(70.0)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Beginning Balance at Mar. 31, 2019	(428.4)	$ 0.0	2,372.1		1.8	(2,802.3)		474.4	$ 0.4	711.8	(34.9)	(202.9)
Other Comprehensive Income (Loss), Net of Tax					(0.8)			(0.9)
Net Income (Loss) Attributable to Parent						(16.1)		29.8
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	(16.9)							28.9
Non-cash capital contribution	(1.5)		(1.5)	[1]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance at Jun. 30, 2019	(446.8)	$ 0.0	2,370.6		1.0	(2,818.4)		433.3	$ 0.4	641.8	(35.8)	(173.1)
Shares, Issued		1							41,172,173
Dividends, Common Stock, Cash								(20.0)		(20.0)
Other Comprehensive Income (Loss), Net of Tax	(1.0)				(1.0)			1.6
Net income/ (loss)	35.4							44.9
Net Income (Loss) Attributable to Parent						35.4		44.9
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	34.4							46.5
Non-cash capital contribution	2.7		2.7	[1]
Stockholders' Equity, Other	0.1		(0.1)					0.0		(0.1)		0.1
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance at Sep. 30, 2019	$ (409.6)	$ 0.0	2,373.4		0.0	(2,783.0)		$ 459.8	$ 0.4	621.9	(34.2)	(128.3)
Common stock, par value (in USD per share)								$ 0.01
Common Stock, Shares Authorized	1,500							50,000,000
Shares, Issued		1							41,172,173
Common Stock, Shares Authorized	1,500							50,000,000
Shares, Issued		1							41,172,173
Common Stock, Value, Issued	$ 0.0							$ 0.4
Additional Paid in Capital, Common Stock	2,370.7							617.0
Accumulated Other Comprehensive Income (Loss), Net of Tax	(3.6)						$ 14.5	(36.9)					$ (0.4)
Retained Earnings (Accumulated Deficit)	(2,739.0)							(107.1)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Beginning Balance at Dec. 31, 2019	(371.9)	$ 0.0	2,370.7		(3.6)	(2,739.0)		473.4
Other Comprehensive Income (Loss), Net of Tax	(0.3)										0.4
Net income/ (loss)	1.9
Net Income (Loss) Attributable to Parent												11.7
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	1.6							12.1
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance at Mar. 31, 2020	(370.3)	0.0	2,370.7		(3.9)	(2,737.1)		485.5	$ 0.4	617.0	(36.5)	(95.4)
Dividends, Common Stock, Cash										(27.7)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Beginning Balance at Dec. 31, 2019	(371.9)	0.0	2,370.7		(3.6)	(2,739.0)		473.4
Other Comprehensive Income (Loss), Net of Tax	0.0						(0.8)	2.2					(0.2)
Net income/ (loss)	(2.8)							47.3
Proceeds from Contributions from Parent	(98.0)							(150.0)
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	(2.8)							49.5
Non-cash capital contribution	0.0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance at Sep. 30, 2020	(276.6)	$ 0.0	2,468.8		(3.6)	(2,741.8)		630.3	$ 0.4	724.4	(34.7)	(59.8)
Shares, Issued		1							41,172,173
Dividends, Common Stock, Cash								(14.2)		(14.2)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Beginning Balance at Mar. 31, 2020	(370.3)	$ 0.0	2,370.7		(3.9)	(2,737.1)		485.5	$ 0.4	617.0	(36.5)	(95.4)
Other Comprehensive Income (Loss), Net of Tax					0.2						0.9
Net Income (Loss) Attributable to Parent						3.5						17.8
Proceeds from Contributions from Parent			(98.0)					(150.0)
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	3.7							18.7
Non-cash capital contribution	98.0
Stockholders' Equity, Other								0.1		0.1
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance at Jun. 30, 2020	(268.6)	$ 0.0	2,468.7		(3.7)	(2,733.6)		640.1	$ 0.4	752.9	(35.6)	(77.6)
Shares, Issued		1							41,172,173
Dividends, Common Stock, Cash								(28.5)		(28.5)
Other Comprehensive Income (Loss), Net of Tax	0.1				0.1			0.9			0.9
Net income/ (loss)	(8.2)							17.8
Net Income (Loss) Attributable to Parent						(8.2)						17.8
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	(8.1)							18.7
Non-cash capital contribution	0.1		0.1
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance at Sep. 30, 2020	$ (276.6)	$ 0.0	$ 2,468.8		$ (3.6)	$ (2,741.8)		$ 630.3	$ 0.4	$ 724.4	$ (34.7)	$ (59.8)
Common stock, par value (in USD per share)	$ 0.01							$ 0.01
Common Stock, Shares Authorized	1,500							50,000,000
Shares, Issued		1							41,172,173
Common Stock, Value, Issued	$ 0.0							$ 0.4
Additional Paid in Capital, Common Stock	2,468.8							724.4
Accumulated Other Comprehensive Income (Loss), Net of Tax	(3.6)						$ 13.7	(34.7)					$ (0.6)
Retained Earnings (Accumulated Deficit)	$ (2,741.8)							$ (59.8)

[1] Represents the conversion of a tax sharing payable to AES to contributed capital, as DP&L's 2017 ESP restricted tax sharing payments to AES during the term of the ESP.