Employee Benefit Plans and Stock-based Compensation (Tables)

6 Months Ended

Jun. 29, 2018

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

Summary of Stock Options Outstanding

The following table summarizes the Company’s stock option activities and related information during the six months endedJune 29, 2018 (in thousands, except per share amounts and terms):

	Stock Options Outstanding
	Number of Shares		Weighted Average Exercise Price Per Share		Weighted Average Remaining Contractual Term (Years)	Aggregate Intrinsic Value
Balance at December 31, 2017	3,880		$	6.04
Granted	—		—
Exercised	(87	)	2.94
Forfeited	(35	)	4.76
Canceled or expired	(538	)	8.75
Balance at June 29, 2018	3,220		5.69		2.8	$	866.8
As of June 29, 2018
Vested and expected to vest	3,208		5.69		2.8	$	859.3
Exercisable	2,958		5.77		2.7	$	696.1

Summary of Restricted Stock Units Outstanding

The following table summarizes the Company’s RSUs activities and related information during the six months ended June 29, 2018 (in thousands, except per share amounts and terms):

	Restricted Stock Units Outstanding
	Number of Shares		Weighted Average Grant Date Fair Value Per Share
Balance at December 31, 2017	2,904		5.09
Granted	3,293		3.74
Vested	(2,220	)	4.75
Forfeited	(183	)	5.09
Balance at June 29, 2018	3,794		4.12

Schedule of Defined Benefit Plans Obligations

The table below presents the components of net periodic benefit costs (in thousands):

	Three months ended				Six months ended
	June 29, 2018		June 30, 2017		June 29, 2018		June 30, 2017
Service cost	$	63	$	55	$	126	$	110
Interest cost	19		16		38		32
Recognized net actuarial loss	—		2		—		3
Net periodic benefit cost	$	82	$	73	$	164	$	145

Summary of Stock-Based Compensation Expense

Stock-based Compensation

The following table summarizes stock-based compensation for all plans (in thousands):

	Three months ended				Six months ended
	June 29, 2018		June 30, 2017		June 29, 2018		June 30, 2017
Stock-based compensation in:
Cost of revenue	$	448	$	700	$	963	$	1,145
Research and development expense	818		1,337		2,622		2,314
Selling, general and administrative expense	1,746		2,099		5,184		3,928
Total stock-based compensation in operating expense	2,564		3,436		7,806		6,242
Total stock-based compensation	$	3,012	$	4,136	$	8,769	$	7,387

Valuation Assumptions for Stock Options

	Stock Options
	Three and six months ended
	June 30, 2017
Expected term (years)	4.3
Volatility	43%
Risk-free interest rate	1.7%
Expected dividends	0.0%

Schedule of Share-based Payment Award, Employee Stock Purchase Plan, Valuation Assumptions

	ESPP Purchase Period Ending
	July 2, 2018		July 3, 2017
Expected term (years)	0.5		0.5
Volatility	60	%	41	%
Risk-free interest rate	1.7	%	1.0	%
Expected dividends	0.0	%	0.0	%
Estimated weighted average fair value per share at purchase date	$1.34		$1.40