Stock-Based Compensation Expense (Tables)

6 Months Ended

Jul. 04, 2021

Share-based Payment Arrangement [Abstract]

Summary of Stock Option Activity

The following table summarizes the Company’s stock option activity for the six-month period ended July 4, 2021:

	Shares (in thousands)	Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value (in thousands)
Outstanding as of December 31, 2020	8,970	$	44.73
Granted	469	89.19
Exercised	(1,167)	38.51
Forfeited or expired	(171)	50.95
Outstanding as of July 4, 2021	8,101	$	48.07	6.91	$	298,370
Exercisable as of July 4, 2021	3,652	$	38.46	5.72	$	168,497
Options vested or expected to vest as of July 4, 2021 (1)	7,474	$	47.27	6.81	$	281,063

 (1) In addition to the vested options, the Company expects a portion of the unvested options to vest at some point in the future. Options expected to vest are calculated by applying an estimated forfeiture rate to the unvested options.

Weighted-Average Assumptions Used in Estimating Fair Values of Stock Options Granted

The fair values of stock options granted in each period presented were estimated using the following weighted-average assumptions:

	Three-months Ended				Six-months Ended
	July 4, 2021		June 28, 2020		July 4, 2021		June 28, 2020
Risk-free rate	1.5	%	1.6	%	1.3	%	1.6	%
Expected dividend yield	0.31	%	0.43	%	0.27	%	0.43	%
Expected volatility	39	%	37	%	39	%	37	%
Expected term (in years)	7.1		6.0		5.8		6.0

Schedule of Nonvested Restricted Stock Units Activity

The following table summarizes the Company's RSUs activity for the six-month period ended July 4, 2021:

	Shares (in thousands)	Weighted-Average Grant Date Fair Value
Nonvested as of December 31, 2020	554	$	51.27
Granted	296	87.46
Vested	(15)	56.61
Forfeited or expired	(27)	54.60
Nonvested as of July 4, 2021	808	$	64.31

Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs

The following table presents the stock-based compensation expense by caption for each period presented on the Consolidated Statements of Operations (in thousands):

	Three-months Ended				Six-months Ended
	July 4, 2021		June 28, 2020		July 4, 2021		June 28, 2020
Cost of revenue	$	351	$	363	$	599	$	717
Research, development, and engineering	3,064		2,401		7,067		7,767
Selling, general, and administrative	7,315		5,254		15,073		14,324
	$	10,730	$	8,018	$	22,739	$	22,808