Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2015

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

Stock Option Activity and Related Information

A summary of the Company’s stock option activity and related information follows:

	Shares			Weighted- average exercise price per share		Weighted- average remaining contractual term (in years)		Aggregate intrinsic value (in thousands)
Outstanding at December 31, 2014		3,294,822		$	9.98		8.08	$	17,985
Granted		1,455,150			12.94
Canceled		(45,939	)		14.97
Forfeited		(335,449	)		14.00
Exercised		(201,622	)		3.58
Outstanding at December 31, 2015		4,166,962		$	10.94		7.81	$	19,163
December 31, 2015:
Options vested and expected to vest		4,117,768		$	10.93		7.80	$	19,074
Options exercisable		2,108,076		$	8.37		6.94	$	15,006

Company's Options Outstanding

The following table summarizes information about the Company’s options outstanding at December 31, 2015:

	Options Outstanding				Options 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		645,113		6.26		589,799		6.19
2.24 – 3.84		317,814		4.28		317,796		4.28
5.12 – 6.72		371,802		6.98		277,781		6.97
8.96 – 10.94		273,276		8.32		113,223		7.82
11.14 – 12.56		283,315		8.49		87,449		8.09
12.77 – 13.93		972,726		9.11		216,977		9.09
14.04 – 16.22		414,690		9.24		64,635		8.45
$17.24 – 20.65		888,226		8.10		440,416		8.10
		4,166,962				2,108,076

Schedule of Weighted Average Fair Value of Options Granted

The following table summarizes information about the Company’s stock option plan for the years ended December 31:

	2015		2014		2013
Fair value of vested stock options (in thousands)	$	6,468	$	3,543	$	920
Aggregate intrinsic value for options exercised (in thousands)	$	2,067	$	2,220	$	681
Weighted-average grant date fair value per share	$	7.20	$	9.45	$	5.30

Stock Compensation Expense

The following table sets forth stock-based compensation expense related to stock-based arrangements under the 2004 Stock Option Plan and the 2013 Equity Incentive Plan for the years ended December 31 as follows (in thousands):

	2015		2014		2013
Cost of revenue	$	471	$	281	$	49
Research and development		1,453		1,018		273
Selling, general and administrative		3,919		3,234		823
Total stock-based compensation expense	$	5,843	$	4,533	$	1,145

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:

	2015	2014	2013
Risk-free interest rates	1.37%–1.97%	1.74%–2.15%	1.05%–1.95%
Expected term (years)	6.25	6.25	6.25
Expected dividend yield	—	—	—
Expected volatility	57.0%	57.0%	57.0%–58.0%