Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2019

Stock-based compensation expense, by award

The Company recorded stock-based compensation expense as follows in the unaudited condensed consolidated statements of income and comprehensive income (dollars in millions):


	Three Months Ended March 31,
	2019		2018
Stock options	$	0.7	$	1.0
Restricted stock awards		0.1		0.2
Restricted stock units		1.9		1.3
Total stock-based compensation	$	2.7	$	2.5

Stock-based compensation expense, cost allocation

The Company recorded stock-based compensation expense as follows in the unaudited condensed consolidated statements of income and comprehensive income (dollars in millions):


	Three Months Ended March 31,
	2019		2018
Costs of product revenue	$	0.4	$	0.4
Selling, general and administrative		1.9		1.7
Research and development		0.4		0.4
Total stock-based compensation	$	2.7	$	2.5

Schedule of stock option activity

Stock option activity for the three months ended March 31, 2019 was as follows:


				Weighted
				Average
		Weighted		Remaining	Aggregate
	Shares Subject	Average		Contractual	Intrinsic Value
	to Options	Option Price		Term (Yrs)	(in millions) (b)
Outstanding at December 31, 2018	2,593,310	$	21.41
Exercised	(167,177)		19.02
Forfeited	(6,212)		21.57
Outstanding at March 31, 2019	2,419,921	$	21.58	5.3	$	40.8

Exercisable at March, 2019	1,658,792	$	19.94	4.9	$	30.7

Exercisable and expected to vest at March 31, 2019 (a)	2,356,595	$	21.48	5.3	$	40.0

(a)

In addition to the options that are vested at March 31, 2019, 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 March 31, 2019.

(b)

The aggregate intrinsic value is based on the positive difference between the fair value of the Company’s common stock price of $38.44 on March 31, 2019 and the exercise price of the underlying stock options.

Restricted stock awards

Stock-Based Compensation

Schedule of restricted stock award and restricted stock unit activity

Restricted stock unit activity for the three months ended March 31, 2019 was as follows:


		Weighted
		Average Grant
	Shares Subject	Date Fair
	to Restriction	Value
Outstanding at December 31, 2018	806,249	$	29.88
Granted	40,713		30.25
Vested	(36,047)		35.47
Forfeited	(9,668)		29.50
Outstanding at March 31, 2019	801,247	$	29.66