Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2016

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

Stock Option Activity and Related Information

A summary of the Company’s stock option activity under the Plans is as follows:

	Shares		Weighted- average exercise price per share		Weighted- average remaining contractual term (in years)	Aggregate intrinsic value (in thousands)
Outstanding at December 31, 2015	4,151,962		$	10.98	7.81	$	18,943
Granted	1,219,675		14.51
Canceled and forfeited	(300,713	)	12.85
Exercised	(348,983	)	7.94
Outstanding at December 31, 2016	4,721,941		$	12.00	7.41	$	48,670
December 31, 2016:
Options vested and expected to vest	4,423,662		$	11.83	7.33	$	46,353
Options exercisable	2,666,260		$	10.03	6.50	$	32,714

Company's Options Outstanding

The following table summarizes information about the Company’s stock options outstanding at December 31, 2016:

	Outstanding		Exercisable
Exercise Price	Number of Shares	Weighted- Average Remaining Contractual Life in Years	Number of Shares	Weighted- Average Remaining Contractual Life in Years
$0.00 – $1.92	520,391	5.21	520,391	5.21
$2.24 – $6.72	589,559	4.64	584,346	4.63
$8.96 – $12.60	510,578	7.58	316,203	7.23
$12.77	754,288	8.12	320,425	8.12
$12.94	654,721	9.10	126,423	9.10
$13.58 – $14.95	365,131	8.59	108,188	7.95
$15.12 – $17.50	364,479	8.64	114,588	8.01
$18.18 – $18.90	736,894	7.09	533,742	7.09
$19.45 – $22.71	225,900	9.17	41,954	7.33
	4,721,941		2,666,260

Restricted Stock Units Award Activity

A summary of RSU activity under the Plans is as follows:

Non-vested RSUs	Share Equivalent		Weighted-Average Grant Date Fair Value
Non-vested at December 31, 2015	15,000		$	12.77
Changes during the year:
Granted	153,602		15.89
Vested	(5,000	)	12.77
Forfeited	—		—
Non-vested at December 31, 2016	163,602		$	15.70

Stock Compensation Expense

The following table sets forth stock-based compensation expense related to stock-based arrangements under the Plans for the years ended December 31 as follows (in thousands):

	2016		2015		2014
Cost of revenue	$	548	$	471	$	281
Research and development	2,046		1,453		1,018
Selling, general and administrative	5,602		3,919		3,234
Total stock-based compensation expense	$	8,196	$	5,843	$	4,533

Fair Value of Employee Option Grant

The fair value of each employee option grant as of December 31 was estimated on the date of grant using the Black-Scholes option pricing model with the following weighted-average assumptions:

	2016	2015	2014
Risk-free interest rates	1.18% – 2.12%	1.37% – 1.97%	1.74% – 2.15%
Expected term (years)	6.22	6.25	6.25
Expected dividend yield	—	—	—
Expected volatility	47.0%	57.0%	57.0%