Benefit Plans (Tables)

12 Months Ended

Dec. 31, 2025

Schedule of Net Periodic Benefit Cost / (Income)

The net periodic benefit cost of the Pension Plans was:

	Years ended December 31,
$ in millions	2025			2024			2023
Service cost	$	2.2		$	2.5		$	3.0
Interest cost	14.5			14.6			15.8
Expected return on assets	(15.8)			(14.8)			(17.6)
Amortization of unrecognized:
Actuarial loss	3.2			2.1			0.6
Prior service cost	1.0			1.0			1.0
Net periodic benefit cost	$	5.1		$	5.4		$	2.8
Rates relevant to each year's expense calculations
Discount rate	5.66		%	5.14		%	5.41		%
Expected return on plan assets	6.05		%	5.15		%	5.40		%
Rate of compensation increase	3.21		%	3.21		%	3.21		%

Schedule of Allocation of Plan Assets

The following table summarizes our target pension plan allocation:

	Long-Term Mid-Point Target Allocation	Percentage of plan assets as of December 31,
Asset category		2025	2024
Equity Securities	32%	31%	31%
Debt Securities	68%	68%	68%
Cash and Cash Equivalents	—%	1%	1%

Other Changes in Plan Assets and Benefit Obligation Recognized in Accumulated Other Comprehensive Income, Regulatory Assets And Regulatory Liabilities

The following table presents other changes in Pension Plan assets and benefit obligations recognized in AOCI / (AOCL), Regulatory assets, non-current and Regulatory liabilities, non-current:

	Years ended December 31,
$ in millions	2025		2024		2023
Net actuarial loss / (gain)	$	(8.1)	$	(2.6)	$	0.7
Plan amendments	—		—		1.4
Reversal of amortization item:
Net actuarial loss	(3.2)		(2.1)		(0.6)
Prior service cost	(1.0)		(1.0)		(1.0)
Total recognized in AOCI / (AOCL), Regulatory assets and Regulatory liabilities	$	(12.3)	$	(5.7)	$	0.5
Total recognized in net periodic benefit cost and AOCI / (AOCL), Regulatory assets and Regulatory liabilities	$	(7.2)	$	(0.3)	$	3.3

Weighted Average Assumptions Used to Determine Benefit Obligations

The weighted average assumptions used to determine benefit obligations were:

Benefit Obligation Assumptions	Pension
	2025	2024
Discount rate	5.52%	5.66%
Rate of compensation increase	3.20%	3.21%

Estimated Future Benefit Payments and Medicare Part D Reimbursements

Benefit payments, which reflect future service, are expected to be paid as follows:

Estimated future benefit payments
$ in millions due within the following years:	Pension
2026	$	20.0
2027	19.9
2028	19.8
2029	19.8
2030	19.7
2031 - 2035	97.0

Schedule of Unrecognized Tax Benefits Roll Forward

$ in millions	2025		2024		2023
Unrecognized tax benefits at January 1	$	0.4	$	0.4	$	0.4
Gross increases - current period tax positions	—		—		—
Gross decreases - prior period tax positions	—		—		—
Unrecognized tax benefits at December 31	$	0.4	$	0.4	$	0.4

Fair Value, Assets Measured on Recurring Basis

The fair value of assets at December 31, 2025 and 2024 and the respective category within the fair value hierarchy was determined as follows:

$ in millions	Fair Value at December 31, 2025								Fair Value at December 31, 2024
	Level 1		Level 2		Level 3		Total		Level 1		Level 2		Level 3		Total
Assets
Master trust assets
Money market funds	$	0.8	$	—	$	—	$	0.8	$	0.4	$	—	$	—	$	0.4
Mutual funds	7.5		—		—		7.5		7.6		—		—		7.6
Total assets	$	8.3	$	—	$	—	$	8.3	$	8.0	$	—	$	—	$	8.0

Pension [Member]

Pension And Postretirement Benefit Plans' Obligations And Assets

The following tables set forth the changes in the Pension Plans' obligations and assets recorded on the Consolidated Balance Sheets at December 31, 2025 and 2024. The amounts presented in the following tables for pension obligations include the collective bargaining plan formula, traditional management plan formula and cash balance plan formula and the SERP in the aggregate and have not been adjusted for $1.3 million, $1.1 million and $0.9 million of costs billed to the Service Company for the years ended December 31, 2025, 2024 and 2023, respectively.

$ in millions	Years ended December 31,
Change in benefit obligation	2025		2024
Benefit obligation at January 1	$	282.4	$	298.6
Service cost	2.2		2.5
Interest cost	14.5		14.6
Actuarial loss / (gain)	2.7		(12.4)
Benefits paid	(35.8)		(20.9)
Benefit obligation at December 31	266.0		282.4
Change in plan assets
Fair value of plan assets at January 1	260.1		268.4
Actual return on plan assets	26.5		5.0
Employer contributions	7.7		7.6
Benefits paid	(35.8)		(20.9)
Fair value of plan assets at December 31	258.5		260.1
Unfunded status of plan	$	(7.5)	$	(22.3)
	December 31,
Amounts recognized in the Consolidated Balance Sheets	2025		2024
Current liabilities	$	(0.2)	$	(0.2)
Non-current liabilities	(7.3)		(22.1)
Net liability at end of year	$	(7.5)	$	(22.3)
Amounts recognized in AOCI / (AOCL), Regulatory assets, non-current, pre-tax
Components:
Prior service cost	$	5.7	$	6.7
Net actuarial loss	62.7		74.0
AOCI / (AOCL), Regulatory assets, pre-tax	$	68.4	$	80.7
Recorded in:
Regulatory asset, non-current	$	47.5	$	56.0
AOCI / (AOCL)	20.9		24.7
AOCI / (AOCL), Regulatory assets, pre-tax	$	68.4	$	80.7

Fair Value Measurements for Plan Assets

The fair values of our Pension Plans' assets at December 31, 2025 by asset category are as follows:

$ in millions	Market Value at December 31, 2025		Quoted prices in active markets for identical assets		Significant observable inputs		Significant unobservable inputs
Asset category			(Level 1)		(Level 2)		(Level 3)
Common collective trusts
Equities (a)	$	81.6	$	—	$	81.6	$	—
Debt securities (b)	117.1		—		117.1		—
Government debt securities (c)	58.2		—		58.2		—
Total common collective trusts	256.9		—		256.9		—
Cash and cash equivalents (d)	1.6		1.6		—		—
Total pension plan assets	$	258.5	$	1.6	$	256.9	$	—

(a)    This category represents investments that invest in equity securities of U.S. companies of any market capitalization and other investments (i.e.: futures, swaps, currency forwards) of foreign, emerging markets and seeks to provide long-term total return, which includes capital appreciation and income. The funds are valued using the net asset value method.

(b)    This category represents investments that invest in high quality issues within the U.S. corporate bond markets and global high yield bonds and emerging markets debt denominated in local currency. The funds seek to provide current income and long-term capital preservation along with access to higher yielding, relatively liquid fixed income securities. The funds are valued using the net asset value method.

(c)    This category represents investments that invest in U.S. treasury strips, U.S. government agency obligations, and U.S. treasury obligations. The funds seek investment returns over the long term and are valued using the net asset value method.

(d)    This category represents an investment that seeks to maximize current income on cash reserves to the extent consistent with principal preservation and maintenance of liquidity from a portfolio of obligations of the U.S. Government, its agencies or municipalities, and related money market instruments. Principal preservation is a primary objective. The fund is valued at cost.

The fair values of our Pension Plans' assets at December 31, 2024 by asset category are as follows:

$ in millions	Market Value at December 31, 2024		Quoted prices in active markets for identical assets		Significant observable inputs		Significant unobservable inputs
Asset category			(Level 1)		(Level 2)		(Level 3)
Common collective trusts
Equities (a)	$	81.3	$	—	$	81.3	$	—
Debt securities (b)	118.9		—		118.9		—
Government debt securities (c)	58.2		—		58.2		—
Total common collective trusts	258.4		—		258.4		—
Cash and cash equivalents (d)	1.7		1.7		—		—
Total pension plan assets	$	260.1	$	1.7	$	258.4	$	—

(a)    This category represents investments that invest in equity securities of U.S. companies of any market capitalization and other investments (i.e.: futures, swaps, currency forwards) of foreign, emerging markets and seeks to provide long-term total return, which includes capital appreciation and income. The funds are valued using the net asset value method.

(b)    This category represents investments that invest in high quality issues within the U.S. corporate bond markets and global high yield bonds and emerging markets debt denominated in local currency. The funds seek to provide current income and long-term capital preservation along with access to higher yielding, relatively liquid fixed income securities. The funds are valued using the net asset value method.

(c)    This category represents investments that invest in U.S. treasury strips, U.S. government agency obligations, and U.S. treasury obligations. The funds seek investment returns over the long term and are valued using the net asset value method.

(d)    This category represents an investment that seeks to maximize current income on cash reserves to the extent consistent with principal preservation and maintenance of liquidity from a portfolio of obligations of the U.S. Government, its agencies or municipalities, and related money market instruments. Principal preservation is a primary objective. The fund is valued at cost.