Stockholders' Equity and Stock-Based Compensation (Tables)

9 Months Ended

Sep. 29, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Employee stock purchase plan assumptions

	Three Months Ended		Nine Months Ended
	September 29, 2018	September 30, 2017	September 29, 2018	September 30, 2017
Employee Stock Purchase Plan:
Expected life	0.5 years	0.5 years	0.5 years	0.5 years
Volatility	52.5%	38.9%	39.1%	37.2%
Risk free interest rate	2.14%	1.13%	1.86%	0.91%
Dividends	—	—	—	—

Stock option plans activity

A summary of activity of stock options during the nine months ended September 29, 2018 is as follows:

	Number of Shares Outstanding (Options)			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value (inThousands)
Options
Outstanding at December 30, 2017		216,326		$	16.82		1.76	$	1,748
Exercised		(132,932	)		17.46
Cancelled		—			—
Outstanding at September 29, 2018		83,394			15.80		1.44		1,811
Exercisable at September 29, 2018		83,394		$	15.80		1.44	$	1,811

Summary of activity for RSUs

A summary of activity for RSUs during the nine months ended September 29, 2018 is as follows:

Summary of activity for RSUs	Number of RSUs			Weighted Average Fair Value
Outstanding RSUs as of December 30, 2017		790,299		$	22.46
Granted		423,891			37.20
Released		(315,621	)		20.51
Cancelled		(131,571	)		25.80
Outstanding RSUs as of September 29, 2018		766,998		$	30.83

Summary of activity for PSUs

A summary of activity for PSUs for the nine months ended September 29, 2018 is as follows:

Summary of activity for PSUs	Number of PSUs			Weighted Average Fair Value
Outstanding PSUs as of December 30, 2017		129,950		$	15.60
Granted		63,133			24.54
Released		(47,929	)		12.14
Cancelled		(32,991	)		25.92
Outstanding PSUs as of September 29, 2018		112,163		$	19.25

PSUs valuation assumptions

The assumptions for the valuation of PSUs are summarized as follows:

	2018 Award		2017 Award
Grant Date Fair Value Per Share	$20.73-$25.18		$	26.75
Weighted-average assumptions/inputs:
Expected Dividend		—		—
Range of risk-free interest rates	2.39%-2.63%		1.40%
Range of expected volatilities for peer group	22%-66%		23%-62%

Stock-based compensation expense for all share-based payment awards

Stock-based compensation expense for all share-based payment awards made to the Company’s employees and directors pursuant to the employee stock option and employee stock purchase plans by function were as follows (in thousands):

	Three Months Ended				Nine Months Ended
	September 29, 2018		September 30, 2017		September 29, 2018		September 30, 2017
Cost of products	$	224	$	216	$	455	$	628
Cost of service		223		161		564		463
Research and development		744		509		1,727		1,262
Selling		779		639		2,049		1,707
General and administrative		1,242		922		3,434		2,715
Total stock-based compensation    expense related to employee    stock options and employee stock    purchases	$	3,212	$	2,447	$	8,229	$	6,775