Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2020

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Schedule of Stock-Based Compensation Expense by Type of Award

The following table details the stock-based compensation expense by type of award for the years ended December 31, 2020, 2019 and 2018:

Summary of Option Activity

A summary of option activity under the plan for the three years ended December 31, 2020 is as follows:

	Number of			Weighted-		Remaining
	Options			Average		Contractual Life
	(In millions)			Exercise Price		(in years)
Outstanding at December 31, 2017		1.7		$	31.18		5.19
Options granted		0.2		$	68.15		—
Options exercised		(0.4	)	$	16.06		—
Outstanding at December 31, 2018		1.5		$	38.97		5.20
Options granted		0.2		$	65.56		—
Options exercised		(0.4	)	$	25.95		—
Outstanding at December 31, 2019		1.3		$	47.92		5.60
Options granted		0.5		$	54.82		—
Options exercised		(0.2	)	$	32.18		—
Outstanding at December 31, 2020		1.6		$	51.07		6.04

Schedule of Other Stock Option Statistics

	Year Ended December 31,
(In millions, except weighted average exercise price)	2020		2019
Aggregate intrinsic value of outstanding options	$	8.3	$	31.8
Aggregate intrinsic value of exercisable options	$	5.7	$	28.0
Total intrinsic value of options exercised	$	2.5	$	22.9
Total number of options exercisable		0.9		0.9
Weighted average exercise price of options exercisable	$	46.29	$	41.00
Total unrecognized compensation cost on non-vested options (a)	$	3.8	$	1.5

(a) Unrecognized compensation cost relates to non-vested stock options and is expected to be recognized over the remaining vesting period ranging from one year to three years.

Schedule of Assumptions Used in Determining the Estimated the Fair Value of Stock Options

We estimated the fair value of stock options at the grant date using the Black-Scholes option pricing model with the following assumptions for the years ended December 31, 2020, 2019 and 2018:

	2020			2019			2018
Risk-free interest rate		0.85	%		2.61	%		2.53	%
Expected option life (in years)		5.96			5.99		5.95
Dividend yield		1.1	%		0.8	%		0.7	%
Volatility		44.35	%		35.05	%		35.64	%
Weighted-average fair value per option granted	$	19.50		$	22.90		$	24.36

Summary of the Company's Service Based RSU Activity

The table presented below provides a summary of the Company’s RSU activity for the years ended December 31, 2020, 2019 and 2018:  

	RSUs			Weighted-Average
	Number of (In millions)			Fair Value Grant Date
Outstanding at December 31, 2017		0.5		$	36.75
RSUs granted		0.1		$	66.63
RSUs issued		(0.1	)	$	41.46
Outstanding at December 31, 2018		0.5		$	41.65
RSUs granted		0.1		$	68.85
RSUs issued		(0.2	)	$	44.75
Outstanding at December 31, 2019		0.4		$	48.06
RSUs granted		0.2		$	51.51
RSUs issued		(0.1	)	$	51.82
Outstanding at December 31, 2020		0.5		$	47.98

Summary of the Company's PRSU Activity

The table presented below provides a summary, of the Company’s PRSU activity, at original grant amounts, for the years ended December 31, 2020, 2019 and 2018:

				Weighted-
	Number of			Average
	PRSUs			Grant Date
	(In millions)			Fair Value
Outstanding at December 31, 2017		0.4		$	45.35
PRSUs granted		0.1		$	68.15
PRSUs issued		(0.2	)	$	43.96
Outstanding at December 31, 2018		0.3		$	51.75
PRSUs granted		0.1		$	65.56
PRSUs issued		(0.1	)	$	41.71
Outstanding at December 31, 2019		0.3		$	60.48
PRSUs granted		0.1		$	74.74
PRSUs issued		(0.1	)	$	50.50
Outstanding at December 31, 2020		0.3		$	68.77