Stockholders' Equity and Stock-Based Compensation (Tables)

3 Months Ended

Apr. 01, 2017

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Employee stock purchase plan assumptions

	Three Months Ended
	April 1, 2017		March 26, 2016
Employee Stock Purchase Plan:
Expected life	0.5 years		0.5 years
Volatility		35.2%		39.1%
Risk free interest rate		0.65%		0.49%
Dividends		—		—

Stock option plans activity

A summary of activity of stock options during the three months ended April 1, 2017 is as follows:

	Number of Shares Outstanding (Options)			Weighted Average Exercise Price
Options
Outstanding at December 31, 2016		440,545		$	15.06
Exercised		(77,644	)	$	15.67
Cancelled		(438	)	$	15.60
Outstanding at April 1, 2017		362,463		$	14.93
Exercisable at April 1, 2017		346,932		$	14.82

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 31, 2016		819,785		$	16.79
Granted		106,245		$	26.13
Released		(103,249	)	$	16.18
Cancelled		(13,151	)	$	15.95
Outstanding RSUs as of April 1, 2017		809,630		$	18.11

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 31, 2016		107,500		$	9.94
Granted		59,550			26.75
Released		(38,500	)		10.41
Cancelled		(4,000	)		12.64
Outstanding PSUs as of April 1, 2017		124,550		$	17.86

PSUs valuation assumptions

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

	2017 Award		2016 Award
Grant Date Fair Value Per Share	$	26.75	$	8.52
Weighted-average assumptions/inputs:
Expected Dividend		—		—
Range of risk-free interest rates		1.40%		0.92%
Range of expected volatilities for peer group	23%-62%		22%-93%

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
	April 1, 2017		March 26, 2016
Cost of products	$	197	$	67
Cost of service		145		104
Research and development		398		285
Selling		540		492
General and administrative		884		741
Total stock-based compensation expense related to employee    stock options and employee stock purchases	$	2,164	$	1,689