Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2022

Share-Based Payment Arrangement [Abstract]

Summary Information for Restricted Stock Awards and Incentive Compensation Stock Awards

The following table summarizes information for restricted stock awards and incentive compensation stock awards for 2022:

	Restricted Stock - Service Based					Restricted Stock - Performance Based					Incentive Compensation Stock
	Number of Awards			Weighted- Average Grant-Date Fair Value		Number of Awards			Weighted- Average Grant-Date Fair Value		Number of Awards			Weighted- Average Grant-Date Fair Value
January 1, 2022		216,075		$	237.80		118,323		$	266.76		37,858		$	288.68
Awarded		65,213		$	362.77		33,148		$	406.99		13,813		$	369.05
Distributed		(62,892	)	$	243.08		(111,070	)	$	202.55		(19,522	)	$	258.20
Forfeited		(2,752	)	$	330.93		(1,424	)	$	338.35		—		$	—
Adjustment for performance		—		$	—		64,818		$	202.55		—		$	—
December 31, 2022		215,644		$	272.86		103,795		$	339.17		32,149		$	341.72

Summary Information for Stock Options

The following table includes summary information for stock options as of December 31, 2022:

	Number of Options			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Life (years)
Outstanding at January 1, 2022		20,564		$	133.59
Exercised		(5,281	)	$	125.02
Outstanding at December 31, 2022		15,283		$	136.55		1.8
Exercisable at December 31, 2022		15,283		$	136.55		1.8

Schedule of Stock-Based Compensation Expense

The following table summarizes stock-based compensation expense for the years ended December 31, 2022, 2021 and 2020, unrecognized compensation cost for nonvested awards at December 31, 2022 and the weighted-average period over which unrecognized compensation cost will be recognized:

(in millions, except year data)	Restricted Stock		Incentive Compensation Stock		Directors’ Awards		Total
Stock-based compensation expense recognized for    years ended December 31:
2022	$	41.0	$	1.1	$	0.6	$	42.7
2021	$	41.4	$	1.0	$	0.6	$	43.0
2020	$	28.5	$	0.8	$	0.7	$	30.0
Unrecognized compensation cost at    December 31, 2022	$	41.5	$	0.9	$	—	$	42.4
Weighted-average period over which unrecognized    compensation cost will be recognized	2.1 years		1.6 years

Stock-Based Compensation Expense in Future for Outstanding Awards

The following presents expected stock-based compensation expense in future periods for outstanding awards as of December 31, 2022:

(in millions)
2023	$	26.1
2024		12.8
2025		2.2
2026		1.1
2027		0.2
Total	$	42.4