Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2021

Disclosure Of Compensation Related Costs Sharebased Payments [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 2021:

	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, 2021		206,981		$	198.28		118,576		$	228.15		42,623		$	223.85
Awarded		68,393		$	342.11		35,067		$	352.52		18,722		$	325.30
Distributed		(56,710	)	$	217.49		(67,451	)	$	219.88		(23,317	)	$	199.79
Forfeited		(2,589	)	$	278.74		(1,777	)	$	267.58		(170	)	$	258.67
Adjustment for performance		—		$	—		33,908		$	219.88		—		$	—
December 31, 2021		216,075		$	237.80		118,323		$	266.76		37,858		$	288.68

Summary Information for Stock Options

The following table includes summary information for stock options as of December 31, 2021:

	Number of Options			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Life (years)
Outstanding at January 1, 2021		31,089		$	129.00
Exercised		(10,385	)	$	120.89
Terminated		(140	)	$	57.71
Outstanding at December 31, 2021		20,564		$	133.59		2.6
Exercisable at December 31, 2021		20,564		$	133.59		2.6

Schedule of Stock-Based Compensation Expense

The following table summarizes stock-based compensation expense for the years ended December 31, 2021, 2020 and 2019, unrecognized compensation cost for nonvested awards at December 31, 2021 and the weighted-average period over which unrecognized compensation cost will be recognized:

(in millions, except year data)	Stock Options		Restricted Stock		Incentive Compensation Stock		Directors’ Awards		Total
Stock-based compensation expense recognized for    years ended December 31:
2021	$	—	$	41.4	$	1.0	$	0.6	$	43.0
2020	$	—	$	28.5	$	0.8	$	0.7	$	30.0
2019	$	0.1	$	32.6	$	0.8	$	0.6	$	34.1
Unrecognized compensation cost at    December 31, 2021	$	—	$	36.9	$	0.9	$	—	$	37.8
Weighted-average period over which unrecognized    compensation cost will be recognized			2.3 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, 2021:

(in millions)
2022	$	21.9
2023		11.8
2024		2.4
2025		1.2
2026		0.5
Total	$	37.8