Stockholders' Equity and Stock-Based Compensation (Tables)

9 Months Ended

Sep. 26, 2015

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Stock options valuation assumptions

	Three Months Ended		Nine Months Ended
	September 26, 2015	September 27, 2014	September 26, 2015	September 27, 2014
Stock Options:
Expected life	—	—	—	4.6 years
Volatility	—	—	—	54.9%
Risk free interest rate	—	—	—	1.54%
Dividends	—	—	—	—
Employee Stock Purchase Plan:
Expected life	0.5 years	0.5 years	0.5 years	0.5 years
Volatility	36.7%	29.6%	36.9%	32.6%
Risk free interest rate	0.13%	0.06%	0.12%	1.00%
Dividends	—	—	—	—

Employee stock purchase plan valuation assumptions

	Three Months Ended		Nine Months Ended
	September 26, 2015	September 27, 2014	September 26, 2015	September 27, 2014
Stock Options:
Expected life	—	—	—	4.6 years
Volatility	—	—	—	54.9%
Risk free interest rate	—	—	—	1.54%
Dividends	—	—	—	—
Employee Stock Purchase Plan:
Expected life	0.5 years	0.5 years	0.5 years	0.5 years
Volatility	36.7%	29.6%	36.9%	32.6%
Risk free interest rate	0.13%	0.06%	0.12%	1.00%
Dividends	—	—	—	—

Stock option plans activity

A summary of activity of stock options during the nine months ended September 26, 2015 is as follows:

	Number of Shares Outstanding (Options)		Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (Years)	Aggregate Intrinsic Value (in Thousands)
Options
Outstanding at December 27, 2014	1,382,993		$	13.92	3.41	$	4,108
Exercised	(191,037	)	9.86
Cancelled	(72,527	)	17.22
Outstanding at September 26, 2015	1,119,429		$	14.40	2.63	$	925
Exercisable at September 26, 2015	948,053		$	14.07	2.28	$	925

Summary of activity for RSUs

A summary of activity for RSUs is as follows:

RSUs	Number of RSUs		Weighted Average Fair Value
Outstanding RSUs as of December 27, 2014	563,337		$	17.90
Granted	448,299		15.64
Released	(223,143	)	16.70
Cancelled	(59,655	)	17.10
Outstanding RSUs as of September 26, 2015	728,838		$	16.02

PSUs valuation assumptions

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

	2015 Award
Number of PSUs granted and outstanding as of September 26, 2015	40,000
Grant Date Fair Value Per Share	$	18.35
Weighted-average assumptions/inputs:
Expected Dividend	—
Range of risk-free interest rates	0.25%-1.1%
Range of expected volatilities for peer group	23%-65%

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 26, 2015		September 27, 2014		September 26, 2015		September 27, 2014
Cost of products	$	96	$	70	$	229	$	199
Cost of service	104		53		195		227
Research and development	300		331		796		967
Selling	511		490		1,403		1,353
General and administrative	671		761		2,041		2,369
Total stock-based compensation expense	$	1,682	$	1,705	$	4,664	$	5,115