Stock-based Compensation (Tables)

3 Months Ended

Mar. 31, 2021

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Compensation Cost and Related Tax Benefits

Compensation cost for the Company’s stock-based awards and the related tax benefits were as follows:

	Three Months Ended March 31,
(in millions)	2021			2020
Stock-based compensation expense	$	5.6		$	5.0
Tax benefit		(1.2	)		(1.1	)
Stock-based compensation expense, net of taxes	$	4.4		$	3.9

Summary of Stock Option Activity

Information on the Company’s stock option activity for the three months ended March 31, 2021 and 2020 is summarized below.

	Three Months Ended March 31,
	2021					2020
(in whole shares and dollars)	Shares			Weighted Average Exercise Price		Shares			Weighted Average Exercise Price
Outstanding, beginning of period		1,282,278		$	93.64		1,121,559		$	87.88
Granted		178,040			115.35		240,705			118.54
Exercised		(67,954	)		80.96		(35,918	)		79.40
Forfeited or cancelled		—			—		—			—
Outstanding, end of period		1,392,364			97.03		1,326,346			93.67

Summary of Activity Information about Employee Restricted Stock Units

The following tables summarize activity information about employee restricted stock units:

	Three Months Ended March 31,
	2021					2020
(in whole shares and dollars)	Shares			Weighted Average Grant Date Fair Value		Shares			Weighted Average Grant Date Fair Value
Time-based restricted stock units:
Outstanding, beginning of period		350,480		$	116.37		335,166		$	109.55
Granted		168,092			115.04		136,634			118.60
Vested		(109,667	)		110.68		(78,773	)		85.44
Forfeited		(7,388	)		116.82		(2,861	)		112.24
Outstanding, end of period		401,517			117.37		390,166			117.56
Performance-based and market-based restricted stock units:
Outstanding, beginning of period		97,043		$	119.59		86,252		$	110.70
Granted		62,143			114.66		54,415			105.10
Vested		(43,506	)		122.27		(36,499	)		80.26
Forfeited		—			—		—			—
Outstanding, end of period		115,680			115.93		104,168			118.45