Stockholders' Equity and Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2019

Share-based Compensation [Abstract]

Schedule of shares reserved for future issuance

The Company had reserved shares of common stock for future issuance as of December 31, 2019 as follows:

Options and RSUs outstanding under equity incentive plans
2000 Equity Incentive Plan	157,385
2012 Equity Incentive Plan	3,924,108
Shares available for future grants under an equity incentive plan
2012 Equity Incentive Plan	5,243,730
Total shares reserved for future issuance	9,325,223

Stock-based employee compensation

The following table shows a summary of the stock-based compensation expense included in the condensed consolidated statements of operations for the fiscal years ended December 31, 2019, 2018 and 2017:

	Year Ended December 31,
	2019		2018		2017
	(in thousands)
Cost of revenues	$	2,262	$	2,489	$	2,159
Research and development	11,151		7,961		5,944
Sales and marketing	4,984		4,650		4,755
General and administrative	16,495		14,990		14,103
Total stock-based employee compensation	$	34,892	$	30,090	$	26,961

Fair value assumptions of options granted to employees

The fair value of each option granted to employees is estimated on the date of grant using the Black-Scholes-Merton option-pricing model based on the following assumptions:

	Year Ended December 31,
	2019	2018	2017
Expected term (in years)	4.4 to 6.6	4.5 to 5.0	5.1 to 5.5
Volatility	40% to 46%	45% to 47%	47% to 49%
Risk-free interest rate	1.5% to 2.4%	2.5% to 3.0%	1.8% to 2.0%
Dividend yield	—	—	—

Stock option activity

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

	Outstanding Shares		Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (Years)	Aggregate Intrinsic Value
						(in thousands)
Balance as of December 31, 2016	7,527,680		$	19.25	6.0	$	101,717
Granted	408,225		$	40.82
Exercised	(2,997,095	)	$	11.05
Canceled	(442,919	)	$	33.29
Balance as of December 31, 2017	4,495,891		$	25.29	6.6	$	153,129
Granted	366,786		$	79.79
Exercised	(1,183,235	)	$	20.33
Canceled	(250,133	)	$	39.61
Balance as of December 31, 2018	3,429,309		$	31.79	6.4	$	149,935
Granted	496,145		$	87.10
Exercised	(901,290	)	$	27.55
Canceled	(157,489	)	$	71.04
Balance as of December 31, 2019	2,866,675		$	40.54	6.0	$	125,647
Vested and expected to vest—December 31, 2019	2,655,987		$	37.27	5.9	$	124,592
Exercisable—December 31, 2019	2,099,200		$	28.39	5.4	$	115,916

Schedule of exercise price range, outstanding and vested

The following table summarizes the outstanding and vested stock options at December 31, 2019:

	Outstanding				Exercisable
Exercise Price	Number of Shares	Weighted Average Exercise Price Per Share		Weighted Average Remaining Contractual Life (Years)	Number of Shares	Weighted Average Exercise Price Per Share
$4.10 - $13.50	297,913	$	9.75	2.5	297,913	$	9.75
$13.60 - $25.17	351,255	$	22.22	4.6	347,391	$	22.19
$25.56 - $25.56	836,635	$	25.56	6.3	764,382	$	25.56
$26.86 - $34.97	297,207	$	30.98	5.0	287,277	$	30.96
$36.25 - $40.68	301,532	$	38.19	6.3	244,236	$	38.17
$40.89 - $79.51	363,278	$	70.50	8.5	113,388	$	61.81
$86.35 - $87.26	196,706	$	86.69	5.5	2,770	$	87.26
$89.55 - $89.55	63,300	$	89.55	9.6	499	$	89.55
$94.45 - $94.45	77,425	$	94.45	9.0	10,458	$	94.45
$95.10 - $95.10	81,424	$	95.10	8.5	30,886	$	95.10
	2,866,675	$	40.54	6.0	2,099,200	$	28.39

Summary of the Company’s RSUs and RSAs activity

A summary of the Company’s RSU activity is as follows:

	Number of Shares		Weighted-Average Grant Date Fair Value Per Share
Balance as of December 31, 2016	587,333		$	28.85
Granted	1,326,849		$	42.69
Vested	(368,367	)	$	33.52
Cancelled	(135,227	)	$	32.04
Balance as of December 31, 2017	1,410,588		$	40.34
Granted	548,245		$	75.44
Vested	(525,375	)	$	39.87
Cancelled	(206,575	)	$	43.43
Balance as of December 31, 2018	1,226,883		$	55.71
Granted	595,985		$	81.59
Vested	(438,892	)	$	53.17
Cancelled	(169,158	)	$	65.51
Balance as of December 31, 2019	1,214,818		$	67.99
Expected to vest as of December 31, 2019	902,794		$	66.37