Stockholders' Equity and Stock-Based Compensation (Tables)

6 Months Ended

Jul. 01, 2017

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Employee stock purchase plan assumptions

	Three Months Ended				Six Months Ended
	July 1, 2017		June 25, 2016		July 1, 2017			June 25, 2016
Employee Stock Purchase Plan:
Expected life	0.5 years		0.5 years		0.5 years			0.5 years
Volatility		35.2%		39.1%		35.2	%		39.1%
Risk free interest rate		0.65%		0.49%		0.65	%		0.49%
Dividends		—		—		—			—

Stock option plans activity

A summary of activity of stock options during the six months ended July 1, 2017 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 31, 2016		440,545		$	15.06		2.12	$	4,405
Exercised		(111,871	)	$	14.66
Cancelled		(438	)	$	15.60
Outstanding at July 1, 2017		328,236		$	15.20		1.76	$	3,313
Exercisable at July 1, 2017		328,236		$	15.20		1.76	$	3,313

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		306,333		$	27.44
Released		(315,228	)	$	17.03
Cancelled		(27,644	)	$	16.01
Outstanding RSUs as of July 1, 2017		783,246		$	20.89

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 July 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				Six Months Ended
	July 1, 2017		June 25, 2016		July 1, 2017		June 25, 2016
Cost of products	$	215	$	89	$	412	$	156
Cost of service		157		114		302		218
Research and development		355		313		754		598
Selling		528		463		1,067		955
General and administrative		908		764		1,792		1,505
Total stock-based compensation expense related to employee    stock options and employee stock purchases	$	2,163	$	1,743	$	4,327	$	3,432