Stockholders' Equity and Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2017

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Employee stock purchase plan assumptions

	Three Months Ended				Nine Months Ended
	September 30, 2017		September 24, 2016		September 30, 2017			September 24, 2016
Employee Stock Purchase Plan:
Expected life	0.5 years		0.5 years		0.5 years			0.5 years
Volatility		38.9%		38.2%		37.2	%		38.7%
Risk free interest rate		1.13%		0.37%		0.91	%		0.44%
Dividends		—		—		—			—

Stock option plans activity

A summary of activity of stock options during the nine months ended September 30, 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		(180,629	)	$	13.58
Cancelled		(855	)	$	16.63
Outstanding at September 30, 2017		259,061		$	16.09		1.81	$	3,293
Exercisable at September 30, 2017		255,665		$	16.06		1.79	$	3,256

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		340,070		$	27.29
Released		(356,619	)	$	16.79
Cancelled		(44,046	)	$	17.21
Outstanding RSUs as of September 30, 2017		759,190		$	21.48

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 September 30, 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				Nine Months Ended
	September 30, 2017		September 24, 2016		September 30, 2017		September 24, 2016
Cost of products	$	216	$	116	$	628	$	273
Cost of service		161		138		463		355
Research and development		509		387		1,262		985
Selling		639		537		1,707		1,492
General and administrative		922		822		2,715		2,327
Total stock-based compensation expense related to employee stock options and employee stock purchases	$	2,447	$	2,000	$	6,775	$	5,432