Common Equity (Tables)

12 Months Ended

Dec. 31, 2023

Stockholders' Equity Note [Abstract]

Schedule of stock-based compensation expense and related tax benefit recognized in income

The following table summarizes our pre-tax stock-based compensation expense and the related tax benefit recognized in income for the years ended December 31:

(in millions)	2023			2022		2021
Stock options	$	5.3		$	6.5	$	6.5
Restricted stock	6.6			7.0		6.1
Performance units	(2.2)		(1)	21.3		3.1
Stock-based compensation expense	$	9.7		$	34.8	$	15.7
Related tax benefit	$	2.7		$	9.6	$	4.3

(1)    The reduction in expense was due to a decrease in the fair value of the outstanding performance units.

Schedule of stock option activity

The following is a summary of our stock option activity during 2023:

Stock Options	Number of Options	Weighted-Average Exercise Price		Weighted-Average Remaining Contractual Life (in years)	Aggregate Intrinsic Value (in millions)
Outstanding as of January 1, 2023	2,909,939	$	77.03
Granted	257,780	93.69
Exercised	(129,743)	48.44
Forfeited	(17,053)	93.34
Expired	(5,172)	91.49
Outstanding as of December 31, 2023	3,015,751	79.57		5.7	$	28.7
Exercisable as of December 31, 2023	2,052,968	73.03		4.6	$	28.7

Schedule of restricted stock activity

The following restricted stock activity occurred during 2023:

Restricted Shares	Number of Shares	Weighted-Average Grant Date Fair Value
Outstanding and unvested as of January 1, 2023	89,885	$	94.73
Granted	75,453	93.69
Released	(61,782)	94.75
Forfeited	(3,158)	94.08
Outstanding and unvested as of December 31, 2023	100,398	93.95

Schedule of shares purchased to fulfill exercised stock options and restricted stock awards

The following is a summary of shares purchased to fulfill exercised stock options and restricted stock awards during the years ended December 31:

(in millions)	2023		2022		2021
Shares purchased	0.2		0.7		0.4
Cost of shares purchased	$	16.6	$	69.2	$	33.1

Schedule of common stock dividends declared

During the year ended December 31, 2023, our Board of Directors declared common stock dividends which are summarized below:

Date Declared	Date Payable	Per Share	Period
January 19, 2023	March 1, 2023	$0.78	First quarter
April 20, 2023	June 1, 2023	$0.78	Second quarter
July 20, 2023	September 1, 2023	$0.78	Third quarter
October 19, 2023	December 1, 2023	$0.78	Fourth quarter