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

12 Months Ended

Dec. 31, 2021

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

Schedule of Accounts, Notes, Loans and Financing Receivable

Accounts receivable are as follows at December 31, 2021 and 2020:

	December 31,
$ in millions	2021		2020
Accounts receivable, net
Customer receivables	$	42.3	$	48.5
Unbilled revenue	19.2		21.6
Amounts due from affiliates	3.1		0.2
Due from PJM transmission enhancement settlement (a)	1.7		1.7
Other	5.5		0.5
Allowance for credit losses	(0.3)		(2.8)
Total accounts receivable, net	$	71.5	$	69.7

(a)    See Note 2 – Regulatory Matters for more information.

Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]

The changes in the components of Accumulated other comprehensive loss during the years ended December 31, 2021 and 2020 are as follows:

$ in millions	Gains / (losses) on cash flow hedges		Change in unfunded pension obligation		Total
Balance at January 1, 2020	$	14.5	$	(18.1)	$	(3.6)
Other comprehensive loss before reclassifications	—		(8.8)		(8.8)
Amounts reclassified from accumulated other comprehensive loss to earnings	(0.9)		1.0		0.1
Net current period other comprehensive loss	(0.9)		(7.8)		(8.7)
Balance at December 31, 2020	13.6		(25.9)		(12.3)
Other comprehensive income before reclassifications	—		6.4		6.4
Amounts reclassified from accumulated other comprehensive loss to earnings	(0.8)		1.9		1.1
Net current period other comprehensive income / (loss)	(0.8)		8.3		7.5
Balance at December 31, 2021	$	12.8	$	(17.6)	$	(4.8)

Reclassification out of Accumulated Other Comprehensive Income [Table Text Block]

The amounts reclassified out of Accumulated other comprehensive loss by component during the years ended December 31, 2021, 2020 and 2019 are as follows:

Details about Accumulated Other Comprehensive Loss Components	Affected line item in the Consolidated Statements of Operations	Years ended December 31,
$ in millions		2021		2020		2019
Gains and losses on cash flow hedges (Note 5):
	Interest expense	(1.0)		(1.1)		(1.2)
	Income tax expense	0.2		0.2		0.1
	Net of income taxes	(0.8)		(0.9)		(1.1)
	Income tax benefit from discontinued operations	—		—		(0.4)
Amortization of defined benefit pension items (Note 8):
	Other expense	2.5		1.3		0.2
	Income tax benefit	(0.6)		(0.3)		—
	Net of income taxes	1.9		1.0		0.2
Total reclassifications for the period, net of income taxes		$	1.1	$	0.1	$	(1.3)

Accounts Receivable, Allowance for Credit Loss

The following table is a rollforward of our allowance for credit losses related to the accounts receivable balances for the years ended December 31, 2021 and 2020:

$ in millions	Beginning Allowance Balance		Current Period Provision		Write-offs Charged Against Allowances		Recoveries Collected		Ending Allowance Balance
2021	$	2.8	$	(0.4)	$	(3.5)	$	1.4	$	0.3
2020	$	0.4	$	3.0	$	(2.3)	$	1.7	$	2.8

Schedule of Cash and Cash Equivalents [Table Text Block]

The following table summarizes cash, cash equivalents and restricted cash amounts reported within the Consolidated Balance Sheets that reconcile to the total of such amounts as shown on the Consolidated Statements of Cash Flows:

	December 31,
$ in millions	2021		2020
Cash and cash equivalents	$	26.6	$	25.4
Restricted cash (included in Prepayments and other current assets)	0.1		0.1
Cash, Cash Equivalents and Restricted Cash, End of Period	$	26.7	$	25.5

THE DAYTON POWER AND LIGHT COMPANY [Member]

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

Schedule of Accounts, Notes, Loans and Financing Receivable

Accounts receivable are as follows at December 31, 2021 and 2020:

	December 31,
$ in millions	2021		2020
Accounts receivable, net
Customer receivables	$	41.6	$	47.6
Unbilled revenue	19.2		21.6
Amounts due from affiliates	4.4		1.9
Due from PJM transmission enhancement settlement (a)	1.7		1.7
Other	5.3		0.2
Allowance for credit losses	(0.3)		(2.8)
Total accounts receivable, net	$	71.9	$	70.2

(a)    See Note 2 – Regulatory Matters for more information.

Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]

$ in millions	Gains / (losses) on cash flow hedges		Change in unfunded pension obligation		Total
Balance at January 1, 2020	$	(0.4)	$	(36.5)	$	(36.9)
Other comprehensive loss before reclassifications	(0.2)		(8.7)		(8.9)
Amounts reclassified from accumulated other comprehensive loss to earnings	0.6		3.1		3.7
Net current period other comprehensive income / (loss)	0.4		(5.6)		(5.2)
Balance at December 31, 2020	—		(42.1)		(42.1)
Other comprehensive income before reclassifications	—		6.4		6.4
Amounts reclassified from accumulated other comprehensive loss to earnings	—		3.9		3.9
Net current period other comprehensive income	—		10.3		10.3
Balance at December 31, 2021	$	—	$	(31.8)	$	(31.8)

Reclassification out of Accumulated Other Comprehensive Income [Table Text Block]

The amounts reclassified out of Accumulated other comprehensive loss by component during the years ended December 31, 2021, 2020 and 2019 are as follows:

Details about Accumulated Other Comprehensive Loss Components	Affected line item in the Statements of Operations	Years ended December 31,
$ in millions		2021		2020		2019
Gains and losses on cash flow hedges (Note 5):
	Interest expense	—		(0.2)		(0.2)
	Income tax expense	—		0.8		—
	Net of income taxes	—		0.6		(0.2)
Amortization of defined benefit pension items (Note 8):
	Other expense	5.0		4.0		3.5
	Income tax benefit	(1.1)		(0.9)		(0.5)
	Net of income taxes	3.9		3.1		3.0
Total reclassifications for the period, net of income taxes		$	3.9	$	3.7	$	2.8

Accounts Receivable, Allowance for Credit Loss

The following table is a rollforward of our allowance for credit losses related to the accounts receivable balances for the years ended December 31, 2021 and 2020:

$ in millions	Beginning Allowance Balance		Current Period Provision		Write-offs Charged Against Allowances		Recoveries Collected		Ending Allowance Balance
2021	$	2.8	$	(0.4)	$	(3.5)	$	1.4	$	0.3
2020	$	0.4	$	3.0	$	(2.3)	$	1.7	$	2.8

Schedule of Cash and Cash Equivalents [Table Text Block]

The following table summarizes cash, cash equivalents and restricted cash amounts reported within the Balance Sheets that reconcile to the total of such amounts as shown on the Statements of Cash Flows:

	December 31,
$ in millions	2021		2020
Cash and cash equivalents	$	14.4	$	11.7
Restricted cash (included in Prepayments and other current assets)	0.1		0.1
Cash, Cash Equivalents and Restricted Cash, End of Period	$	14.5	$	11.8