The Company grants RSUs to employees and directors under the 2014 Stock Incentive Plan (the “2014 Plan”). The 2014 Plan is administered by the Compensation Committee of the Company’s Board of Directors. The 2014 Plan is intended to attract and retain employees and directors, and to provide an incentive for these individuals to assist the Company to achieve long-range performance goals and to enable these individuals to participate in the long-term growth of the Company.

The total stock-based compensation expense included in the Company’s condensed consolidated statements of operations and comprehensive income was as follows:

	Three Months Ended June 30,				Six Months Ended June 30,
	2021		2020		2021		2020
Cost of revenues	$	0.8	$	0.9	$	1.8	$	1.9
Research and development		1.1		0.9		2.2		2.0
Selling, general and administrative		6.9		4.9		14.8		10.8
Acquisition and integration costs		—		0.1		—		0.6
Total pre-tax stock-based compensation expense	$	8.8	$	6.8	$	18.8	$	15.3

At June 30, 2021, the total compensation expense related to unvested stock-based awards granted to employees and directors under the 2014 Plan that had not been recognized was $51.5. The Company determines the fair value of RSUs based on the closing market price of the Company’s common stock on the date of the award and estimates the fair value of SARs and employee stock purchase plan rights using the Black-Scholes valuation model. Such values are recognized as expense on a straight-line basis for time-based awards and using the accelerated graded vesting method for performance-based awards, both over the requisite service periods.

	Six Months Ended June 30, 2021
	Outstanding RSUs			Weighted Average Grant Date Fair Value
RSUs – beginning of period		0.6		$	93.26
Granted		0.2		$	178.71
Vested		(0.3	)	$	95.08
RSUs – end of period		0.5		$	126.56

The Company had an immaterial amount of SARs outstanding as of June 30, 2021 and December 31, 2020.