Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2020

Stock-Based Compensation

Stock-based compensation expense, by award

	Three Months Ended September 30,				Nine Months Ended September 30,
	2020		2019		2020		2019
Stock options	$	0.6	$	0.7	$	1.5	$	2.1
Restricted stock awards		—		0.1		—		0.3
Restricted stock units		3.5		2.7		8.4		6.3
Total stock-based compensation	$	4.1	$	3.5	$	9.9	$	8.7

Stock-based compensation expense, cost allocation

	Three Months Ended September 30,				Nine Months Ended September 30,
	2020		2019		2020		2019
Costs of product revenue	$	0.6	$	0.5	$	1.5	$	1.3
Selling, general and administrative		2.9		2.5		6.9		6.1
Research and development		0.6		0.5		1.5		1.3
Total stock-based compensation	$	4.1	$	3.5	$	9.9	$	8.7

Summary of volatility, expected life, dividend yield and risk-free interest rates required for the Black-Scholes model

	Nine months ended
	September 30,
	2020		2019
Risk-free interest rates	0.23	%	1.55	%
Expected life	5.14	years	5.33	years
Volatility	34	%	30	%
Expected dividend yield	0.37	%	0.38	%

Schedule of stock option activity

				Weighted
				Average
		Weighted		Remaining	Aggregate
	Shares Subject	Average		Contractual	Intrinsic Value
	to Options	Option Price		Term (Yrs)	(in millions) (b)
Outstanding at December 31, 2019	1,988,696	$	23.43
Granted	125,794	$	45.54
Exercised	(117,611)	$	20.91
Forfeited/Expired	(14,302)	$	20.98
Outstanding at September 30, 2020	1,982,577	$	24.96	4.5	$	30.5
Exercisable at September 30, 2020	1,518,484	$	21.88	4.1	$	27.3
Exercisable and expected to vest at September 30, 2020 (a)	1,938,555	$	24.56	4.4	$	30.5

(a) In addition to the options that are vested at September 30, 2020, the Company expects a portion of the unvested options to vest in the future. Options expected to vest in the future are determined by applying an estimated forfeiture rate to the options that are unvested as of September 30, 2020.

(b) The aggregate intrinsic value is based on the positive difference between the fair value of the Company’s common stock price on September 30, 2020 and the exercise price of the underlying stock options.

Restricted stock awards

Stock-Based Compensation

Schedule of restricted stock unit activity

		Weighted
		Average Grant
	Shares Subject	Date
	to Restriction	Value
Outstanding at December 31, 2019	865,101	$	34.73
Granted	333,081	$	43.99
Vested	(283,048)	$	33.42
Forfeited	(48,297)	$	35.68
Outstanding at September 30, 2020	866,837	$	38.66