Employee Benefit Plans and Stock-based Compensation (Tables)

6 Months Ended

Jun. 30, 2017

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

Summary of Company's Stock Option and Restricted Stock Unit Activity

			Stock Options Outstanding				RSUs Outstanding*
	Shares Available for Grant		Number of Shares		Weighted Average Exercise Price		Number of Units		Weighted Average Grant Date Fair Value
Balance at December 31, 2016	3,912		5,019		$	6.01	3,864		$	4.26
Authorized	7,400		—		—		—		—
Granted	(4,008	)	30		5.10		2,651		5.46
Options exercised	—		(94	)	3.06		—
Shares released	—		—		—		(1,883	)	3.92
Forfeited	1,584		(469	)	6.13		(744	)	4.96
Balance at June 30, 2017	8,888		4,486		$	6.06	3,888		$	5.11

Summary of Stock Options Outstanding

The following table summarizes information about stock options outstanding as of June 30, 2017 (in thousands, except per share amounts and terms):

	Number of Shares	Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (Years)	Aggregate Intrinsic Value
Vested and expected to vest	4,389	$	6.08	3.2	$	2,045
Exercisable	3,497	6.33		2.7	1,079

Summary of Restricted Stock Units Outstanding

The following table summarizes information about RSUs and PRSUs outstanding as of June 30, 2017 (in thousands, except term):

	Number of Shares Underlying Restricted Stock Units	Weighted Average Remaining Vesting Period (Years)	Aggregate Fair Value
Vested and expected to vest	2,893	0.9	$	15,190

Schedule of Defined Benefit Plans Obligations

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

	Three months ended				Six months ended
	June 30, 2017		July 1, 2016		June 30, 2017		July 1, 2016
Service cost	$	55	$	71	$	110	$	94
Interest cost	16		29		32		39
Recognized net actuarial loss	2		—		3		—
Net periodic benefit cost included in operating loss	$	73	$	100	$	145	$	133

Summary of Stock-Based Compensation Expense

Stock-based Compensation

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

	Three months ended				Six months ended
	June 30, 2017		July 1, 2016		June 30, 2017		July 1, 2016
Stock-based compensation in:
Cost of revenue	$	700	$	424	$	1,145	$	651
Research and development expense	1,337		841		2,314		1,810
Selling, general and administrative expense	2,099		1,503		3,928		3,401
Total stock-based compensation in operating expense	3,436		2,344		6,242		5,211
Total stock-based compensation	$	4,136	$	2,768	$	7,387	$	5,862

Valuation Assumptions for Stock Options

	Employee Stock Options
	Three months ended				Six months ended
	June 30, 2017		July 1, 2016		June 30, 2017		July 1, 2016
Expected term (years)	4.30		4.30		4.30		4.30
Volatility	43	%	36	%	43	%	36	%
Risk-free interest rate	1.7	%	1.1	%	1.7	%	1.4	%
Expected dividends	0.0	%	0.0	%	0.0	%	0.0	%

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

	ESPP Purchase Period Ending
	July 3, 2017		June 30, 2016
Expected term (years)	0.49		0.5
Volatility	41	%	54	%
Risk-free interest rate	1.0	%	0.4	%
Expected dividends	0.0	%	0.0	%
Estimated weighted average fair value per share at purchase date	$1.40		$1.19