Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2021

Accounting Policies [Abstract]

Schedule of inventory

Our inventory as of December 31 consisted of:

(in millions)	2021		2020
Natural gas in storage	$	326.0	$	224.9
Materials and supplies	225.3		218.1
Fossil fuel	84.5		85.6
Total	$	635.8	$	528.6

Schedule of annual utility composite depreciation rates

Annual utility composite depreciation rates are shown below:

Annual Utility Composite Depreciation Rates	2021	2020	2019
WE	3.09%	3.19%	3.11%
WPS	2.66%	2.63%	2.44%
WG	2.44%	2.33%	2.29%
PGL	3.12%	3.16%	3.20%
NSG	2.52%	2.48%	2.48%
MERC	2.58%	2.47%	2.33%
MGU	2.70%	2.67%	2.54%
UMERC	2.94%	2.97%	2.87%

Schedule of AFUDC rates and amounts

Average AFUDC rates are shown below:

	2021
	Average AFUDC Retail Rate	Average AFUDC Wholesale Rate
WE	8.68%	1.79%
WPS	7.55%	1.04%
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)	2021		2020		2019
AFUDC – Debt
WE	$	2.9	$	2.6	$	1.5
WPS	3.5		4.6		2.4
WG	0.2		0.6		0.5
UMERC	0.1		—		1.3
WBS	0.1		0.1		0.1
Other	—		0.1		0.1
Total AFUDC – Debt	$	6.8	$	8.0	$	5.9
AFUDC – Equity
WE	$	7.9	$	7.0	$	3.7
WPS	9.0		11.8		5.7
WG	0.6		1.6		1.3
UMERC	0.1		0.1		3.3
WBS	0.2		0.2		0.2
Other	0.2		0.2		0.2
Total AFUDC – Equity	$	18.0	$	20.9	$	14.4

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:

	2021			2020			2019
Stock options granted	530,612			554,594			476,418
Estimated weighted-average fair value per stock option	$	13.20		$	10.94		$	8.60
Assumptions used to value the options:
Risk-free interest rate	0.1% – 0.9%			0.2% – 1.9%			2.5% – 2.7%
Dividend yield	2.9		%	3.0		%	3.6		%
Expected volatility	21.0		%	16.3		%	17.0		%
Expected life (years)	8.7			8.6			8.5