Stockholders' Equity and Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Employee stock purchase plan assumptions

	Three Months Ended
	March 31, 2018	April 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 three months ended March 31, 2018 is as follows:

	Number of Shares Outstanding (Options)			Weighted Average Exercise Price
Options
Outstanding at December 30, 2017		216,326		$	16.82
Exercised		(43,614	)		16.13
Cancelled		—			—
Outstanding at March 31, 2018		172,712			16.99
Exercisable at March 31, 2018		172,712		$	16.99

Summary of activity for RSUs

A summary of activity for RSUs 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		109,007			26.58
Released		(84,942	)		18.88
Cancelled		(42,668	)		22.15
Outstanding RSUs as of March 31, 2018		771,696		$	23.45

Summary of activity for PSUs

A summary of activity for PSUs 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		24,640			21.10
Released		(47,929	)		12.10
Cancelled		(15,621	)		26.21
Outstanding PSUs as of March 31, 2018		91,040		$	18.47

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-$21.97		$14.57-$26.75
Weighted-average assumptions/inputs:
Expected Dividend		—		—
Range of risk-free interest rates	2.39%-2.41%		1.40%-1.84%
Range of expected volatilities for peer group	22%-66%		22%-66%

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
	March 31, 2018		April 1, 2017
Cost of products	$	99	$	197
Cost of service		155		145
Research and development		476		398
Selling		533		540
General and administrative		1,075		884
Total stock-based compensation expense related to employee    stock options and employee stock purchases	$	2,338	$	2,164