Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2022

Accounting Policies [Abstract]

Schedule of inventory

Our inventory as of December 31 consisted of:

(in millions)	2022		2021
Natural gas in storage	$	446.3	$	326.0
Materials and supplies	257.0		225.3
Fossil fuel	103.8		84.5
Total	$	807.1	$	635.8

Schedule of annual utility composite depreciation rates

Annual utility composite depreciation rates are shown below:

Annual Utility Composite Depreciation Rates	2022	2021	2020
WE	3.06%	3.09%	3.19%
WPS	2.67%	2.66%	2.63%
WG	2.47%	2.44%	2.33%
PGL	3.13%	3.12%	3.16%
NSG	2.43%	2.52%	2.48%
MERC	2.56%	2.58%	2.47%
MGU	2.75%	2.70%	2.67%
UMERC	3.01%	2.94%	2.97%

Schedule of AFUDC rates and amounts

Average AFUDC rates are shown below:

	2022
	Average AFUDC Retail Rate	Average AFUDC Wholesale Rate
WE	8.68%	5.35%
WPS	7.55%	5.49%
WG	8.32%	N/A
UMERC	6.28%	N/A
WBS	7.55%	N/A

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

(in millions)	2022		2021		2020
AFUDC–Debt
WE	$	6.9	$	2.9	$	2.6
WPS	2.3		3.5		4.6
WG	1.4		0.2		0.6
UMERC	0.1		0.1		—
WBS	0.1		0.1		0.1
Other	0.2		—		0.1
Total AFUDC–Debt	$	11.0	$	6.8	$	8.0
AFUDC–Equity
WE	$	18.8	$	7.9	$	7.0
WPS	5.8		9.0		11.8
WG	3.9		0.6		1.6
UMERC	0.1		0.1		0.1
WBS	0.3		0.2		0.2
Other	0.5		0.2		0.2
Total AFUDC–Equity	$	29.4	$	18.0	$	20.9

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:

	2022			2021			2020
Stock options granted	437,269			530,612			554,594
Estimated weighted-average fair value per stock option	$	14.71		$	13.20		$	10.94
Assumptions used to value the options:
Risk-free interest rate	0.2% – 1.6%			0.1% – 0.9%			0.2% – 1.9%
Dividend yield	3.2		%	2.9		%	3.0		%
Expected volatility	21.0		%	21.0		%	16.3		%
Expected life (years)	8.7			8.7			8.6