Overview and Summary of Significant Accounting Policies Overview and Summary of Significant Accounting Polices (Tables)

12 Months Ended

Dec. 31, 2018

Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]

Schedule of Cash and Cash Equivalents [Table Text Block]

The following table provides a summary of cash, cash equivalents, and restricted cash amounts reported on the Consolidated Balance Sheet that reconcile to the total of such amounts as shown on the Consolidated Statements of Cash Flows:

$ in millions	December 31, 2018		December 31, 2017
Cash and cash equivalents	$	90.5	$	24.5
Restricted cash	21.2		0.4
Cash, Cash Equivalents, and Restricted Cash, End of Period	$	111.7	$	24.9

THE DAYTON POWER AND LIGHT COMPANY [Member]

Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]

Schedule of Cash and Cash Equivalents [Table Text Block]

The following table provides a summary of cash, cash equivalents, and restricted cash amounts reported on theBalance Sheet that reconcile to the total of such amounts as shown on the Statements of Cash Flows:

$ in millions	December 31, 2018		December 31, 2017
Cash and cash equivalents	$	45.0	$	5.2
Restricted cash	21.2		0.4
Cash, Cash Equivalents, and Restricted Cash, End of Period	$	66.2	$	5.6