Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2024

Accounting Policies [Abstract]

Schedule of inventory

Our inventories as of December 31 consisted of:

(in millions)	2024		2023
Materials and supplies	$	412.5	$	320.0
Natural gas in storage	300.2		327.8
Fossil fuel	100.5		127.4
Total	$	813.2	$	775.2

Schedule of annual utility composite depreciation rates

Annual utility composite depreciation rates are shown below:

Annual Utility Composite Depreciation Rates	2024	2023	2022
WE	3.03%	3.03%	3.06%
WPS	2.92%	2.93%	2.67%
WG	2.61%	2.61%	2.47%
PGL	3.36%	3.13%	3.13%
NSG	2.49%	2.46%	2.43%
MERC	2.60%	2.60%	2.56%
MGU	2.87%	2.73%	2.75%
UMERC	3.01%	2.97%	3.01%

Schedule of AFUDC rates and amounts

Average AFUDC rates are shown below:

	2024
	Average AFUDC Retail Rate	Average AFUDC Wholesale Rate
WE	8.45%	7.11%
WPS	7.46%	5.53%
WG	7.94%	N/A
UMERC	6.28%	N/A
WBS	7.46%	N/A

Our regulated utilities and WBS recorded the following AFUDC for the years ended December 31:

(in millions)	2024		2023		2022
AFUDC-Debt
WE	$	14.6	$	13.0	$	6.9
WPS	3.6		2.9		2.3
WG	1.0		3.4		1.4
UMERC	0.4		—		0.1
WBS	0.1		0.1		0.1
Other	0.2		0.1		0.2
Total AFUDC-Debt	$	19.9	$	19.5	$	11.0
AFUDC-Equity
WE	$	46.0	$	41.0	$	18.8
WPS	9.2		7.6		5.8
WG	2.9		9.8		3.9
UMERC	1.0		—		0.1
WBS	0.3		0.4		0.3
Other	0.4		0.3		0.5
Total AFUDC-Equity	$	59.8	$	59.1	$	29.4

Schedule of assumptions used to estimate the fair value of stock options granted

The following table shows the estimated weighted-average fair value per stock option granted along with the weighted-average assumptions used in the valuation models:

	2024			2023			2022
Stock options granted	294,990			257,780			437,269
Estimated weighted-average fair value per stock option	$	16.19		$	19.58		$	14.71
Assumptions used to value the options:
Risk-free interest rate	3.9% – 5.4%			3.8% – 4.8%			0.2% – 1.6%
Dividend yield	3.8		%	3.2		%	3.2		%
Expected volatility	22.0		%	22.0		%	21.0		%
Expected life (years)	8.4			8.3			8.7