Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2019

Share-based Payment Arrangement [Abstract]

Summary of Assumptions Used to Estimate the Fair Value of Stock Options Granted

The following table summarizes the assumptions used to estimate the fair value of stock options granted during the years ended December 31, 2019, 2018 and 2017:

	2019	2018	2017
Risk-free interest rate	2.1%	*	1.9% - 2.2%
Expected term (in years)	2.6	*	6.5
Expected volatility	55.0%	*	38.1% - 40.6%
Expected dividend yield	—%	*	—%

* Not applicable because no stock options were granted during the period.

Summary of the Stock Option Activity

The following table summarizes the stock option activity for the years ended December 31, 2019, 2018 and 2017:

	Number of Shares	Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (Years)	Aggregate Intrinsic Value (in thousands)
Outstanding at January 1, 2017	6,784,448	$	4.65	6.5	$	44,259
Granted	1,256,200	11.92
Exercised	(876,121)	1.27			14,807
Canceled	(153,640)	7.29
Outstanding at December 31, 2017	7,010,887	6.36		6.6	176,122
Granted	—	—
Exercised	(1,486,218)	2.10			41,606
Canceled	(503,601)	9.51
Outstanding at December 31, 2018	5,021,068	7.30		6.4	97,440
Granted	700,000	33.98
Exercised	(1,194,471)	4.11			44,081
Canceled	(67,986)	10.17
Outstanding at December 31, 2019	4,458,611	12.30		5.8	115,501
Exercisable at December 31, 2019	2,818,731	7.51		5.7	86,536

Schedule of Restricted Stock Unit Activity

The following table summarizes the restricted stock unit activity for the years ended December 31, 2019, 2018 and 2017:

	Number of Shares	Weighted Average Grant Date Fair Value
Non-vested outstanding at January 1, 2017	—	$	—
Granted	738,055	22.15
Vested	(4,930)	20.24
Canceled	(1,150)	21.40
Non-vested outstanding at December 31, 2017	731,975	22.16
Granted	622,166	29.60
Vested	(143,390)	22.19
Canceled	(35,702)	23.97
Non-vested outstanding at December 31, 2018	1,175,049	26.04
Granted	436,912	40.70
Vested	(521,460)	27.81
Canceled	(67,666)	26.38
Non-vested outstanding at December 31, 2019	1,022,835	31.39

Schedule of Components of Stock-based Compensation Expense

The following table summarizes the components of our stock-based compensation expense for the years ended December 31, 2019, 2018 and 2017 (in thousands):

	2019		2018		2017
Stock-based compensation expense related to stock options	$	3,408	$	7,947	$	9,607
Stock-based compensation expense related to restricted stock units	12,667		7,714		753
Stock-based compensation expense related to the issuance of common stock to directors	368		393		222
Stock-based compensation expense related to stock option modifications	—		—		2,394
Total stock-based compensation expense	$	16,443	$	16,054	$	12,976

Schedule of Stock-based Compensation Expense Included in Condensed Consolidated Statements of Operations

Stock-based compensation expense for restricted stock units, stock options and issuances of common stock is included in the following line items in the accompanying consolidated statements of operations for the years ended December 31, 2019, 2018 and 2017 (in thousands):

	2019		2018		2017
Cost of revenue
Subscriptions	$	647	$	514	$	575
Professional services	2,748		1,717		1,295
Operating expenses
Sales and marketing	4,742		3,473		3,233
Research and development	3,480		2,416		2,822
General and administrative	4,826		7,934		5,051
Total stock-based compensation expense	$	16,443	$	16,054	$	12,976