Common stock (Tables)

12 Months Ended

Dec. 31, 2019

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

Schedule of Reserved Shares for Issuance

At December 31, 2019, the Company has 2,003,979 shares of common stock reserved for issuance under stock option plans.

Schedule of Stock Option Activity

The following table summarizes the combined stock option activity under the 2000 Plan, the 2006 Plan and the 2012 Plan and non-plan stock option agreements:

	Options outstanding
	Number of options		Weighted average exercise price		Weighted average remaining contractual term	Aggregate intrinsic value
					(in years)	(in thousands)
Outstanding at December 31, 2018	797,501		$	13.31	4.71	$	20,767
Options granted	—		—
Options exercised	(187,174	)	13.03
Options canceled	(4,000	)	10.41
Outstanding at December 31, 2019	606,327		$	13.41	3.62	$	4,566
Options vested and expected to vest as of December 31, 2019	606,327		$	13.41	3.62	$	4,566
Options vested and exercisable as of December 31, 2019	606,327		$	13.41	3.62	$	4,566

Options, Grants in Period, Wtd Avg Grant Date Fair Value

No options were granted during the years ended December 31, 2019, 2018 and 2017. Further information regarding the value of employee options vested and exercised during the years ended December 31, 2019, 2018 and 2017 is set forth below.

	Years ended December 31,
(in thousands)	2019		2018		2017
Intrinsic value of options exercised during period	$	3,700	$	10,243	$	18,603

Schedule of Valuation Assumptions for ESPP

The Company uses the Black-Scholes option-pricing model to calculate the fair value of periodic ESPP offerings on their offer date. The following assumptions were used for each respective period for the ESPP:

	Years ended December 31,
	2019	2018	2017
Expected term (in years)	0.5	0.5	0.5
Volatility	33% - 50%	33% - 37.8%	29.0% - 32.0%
Risk-free interest rate	1.59% - 2.51%	2.09% - 2.51%	0.61% - 1.39%
Dividend yield	0.0%	0.0%	0.0%

Summary of the restricted stock activty

A summary of the restricted stock activity for the year ended December 31, 2019 is presented below:

	Restricted Stock Units
	Number of shares		Weighted Average Grant Date Fair Value per Share
Outstanding at December 31, 2018	1,807,180		$	23.13
Granted	845,437		31.88
Vested	(978,785	)	20.89
Forfeited	(123,186	)	27.78
Outstanding at December 31, 2019	1,550,646		$	28.94

Schedule of Share-based Comp Allocation of Period Costs

The following table presents the allocation of stock-based compensation expense:

	Years ended December 31,
(in thousands)	2019		2018		2017
Cost of revenue	$	4,441	$	3,614	$	2,871
Research and development	3,955		2,976		2,122
Sales and marketing	7,014		6,560		6,563
General and administrative	8,455		7,814		6,640
Total stock-based compensation	$	23,865	$	20,964	$	18,196