Stockholders' Equity and Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Employee stock purchase plan assumptions

	Six Months Ended
	June 30, 2018	July 1, 2017
Employee Stock Purchase Plan:
Expected life	0.5 years	0.5 years
Volatility	27.2%	35.2%
Risk free interest rate	1.61%	0.65%
Dividends	—	—

Stock option plans activity

A summary of activity of stock options during the six months ended June 30, 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	$	4,405
Exercised		(72,602	)		16.57
Cancelled		—			—
Outstanding at June 30, 2018		143,724			16.94		1.28		2,654
Exercisable at June 30, 2018		143,724		$	16.94		1.28	$	2,654

Summary of activity for RSUs

A summary of activity for RSUs during the six months ended June 30, 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		387,089			36.57
Released		(288,145	)		20.62
Cancelled		(110,294	)		24.50
Outstanding RSUs as of June 30, 2018		778,949		$	29.86

Summary of activity for PSUs

A summary of activity for PSUs for the six months ended June 30, 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 June 30, 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				Six Months Ended
	June 30, 2018		July 1, 2017		June 30, 2018		July 1, 2017
Cost of products	$	133	$	215	$	231	$	412
Cost of service		186		157		341		302
Research and development		506		355		983		754
Selling		737		528		1,270		1,067
General and administrative		1,117		908		2,192		1,792
Total stock-based compensation expense related to employee    stock options and employee stock purchases	$	2,679	$	2,163	$	5,017	$	4,327