Stock-Based Compensation Expense (Tables)

6 Months Ended

Jun. 30, 2017

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

Schedule of Stock-Based Compensation Expense

Stock-based compensation expense for restricted stock, restricted stock units, stock options and issuances of common stock pursuant to our employee stock purchase plan was classified in the accompanying consolidated statements of operations as follows:

	Three Months Ended June 30,				Six Months Ended June 30,
	2017		2016		2017		2016
	(in thousands)
Stock-based compensation expense:
Cost of revenue	$	308	$	142	$	510	$	279
Research and development	1,689		1,524		3,202		3,017
Sales and marketing	1,779		1,224		3,182		4,125
General and administrative	1,395		751		2,556		1,739
Total stock-based compensation expense	$	5,171	$	3,641	$	9,450	$	9,160

Summary of Restricted Stock and Restricted Stock Unit Activity

Restricted stock and restricted stock unit activity during the six months ended June 30, 2017 was as follows:

	Restricted Stock				Restricted Stock Units
	Shares		Weighted-Average Grant Date Fair Value		Shares		Weighted-Average Grant Date Fair Value
Unvested balance as of December 31, 2016	585,004		$	18.05	734,577		$	13.47
Granted	—		—		1,423,010		14.11
Vested	(156,765	)	19.04		(200,416	)	13.72
Forfeited	(7,698	)	23.01		(78,441	)	13.62
Unvested balance as of June 30, 2017	420,541		$	17.59	1,878,730		$	13.92

Summary of Stock Option Activity

Stock option activity during the six months ended June 30, 2017 was as follows:

	Shares		Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (in years)	Aggregate Intrinsic Value (in thousands)
Outstanding as of December 31, 2016	4,580,375		$	8.20
Granted	1,266,238		13.38
Exercised	(670,533	)	6.13			$	7,572
Forfeited/cancelled	(134,812	)	12.41
Outstanding as of June 30, 2017	5,041,268		$	9.66	7.5	$	36,564
Vested and exercisable as of June 30, 2017	2,642,121		$	6.57	6.0	$	27,278
Vested and expected to vest as of June 30, 2017	4,544,979		$	9.27	7.1	$	34,726