Stockholders' Equity and Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2021

Stockholders Equity And Stock Based Compensation [Abstract]

Summary of Number of Shares of Common Stock Reserved

The number of shares of common stock reserved for the vesting of restricted stock units (“RSUs”), and exercise of common stock options are as follows (in thousands):

	December 31, 2021		December 31, 2020
RSUs		1,239		1,561
Common stock options		584		1,020
		1,823		2,581

Schedule of Stock Compensation Expense by Award Type

The following two tables show stock compensation expense by award type and where the stock compensation expense is recorded in the Company’s consolidated statements of operations:

	Year Ended December 31,
	2021		2020		2019
	( in thousands)
Options	$	6,253	$	6,377	$	5,078
ESPP		9,123		6,850		4,866
RSUs		151,385		108,261		87,810
Total stock-based compensation	$	166,761	$	121,488	$	97,754

Effect of Stock-Based Compensation on Income by Line Item

The following two tables show stock compensation expense by award type and where the stock compensation expense is recorded in the Company’s consolidated statements of operations:

	2021		2020		2019
	(in thousands)
Cost of revenue, subscription	$	6,297	$	4,408	$	3,127
Cost of revenue, service		3,092		2,536		2,829
Research and development		61,614		39,366		33,748
Sales and marketing		67,413		50,552		36,599
General and administrative		28,345		24,626		21,451
Total stock-based compensation	$	166,761	$	121,488	$	97,754

Schedule of Assumptions Used for Estimation of Fair Value of Options Granted to Employees

Stock Options —The fair value of employee options is estimated on the date of each grant using the Black-Scholes option-pricing model with the following assumptions:

	Year Ended December 31,
	2021		2020		2019
Risk-free interest rate (%)	0.53-1.36		0.47-1.66		1.95-2.55
Expected term (years)	5.2-6.4		5.50-6.24		5.50-6.02
Volatility (%)	42.97-44.70		38.15-40.63		39.46-41.41
Expected dividends		—		—		—

Summary of Stock Option Activity

The stock option activity for the year ended December 31, 2021 is as follows:

	Options (in thousands)			Weighted- Average Exercise Price		Weighted- Average Remaining Life (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding—January 1, 2021		1,020		$	57.98		4.4	$	345,144
Granted	63				480.08
Exercised		(457	)	35.57
Forfeited/expired		(42	)	174.03
Outstanding—December 31, 2021		584		$	112.82		4.7	$	320,882
Options vested or expected to vest—December 31, 2021		584		$	112.82		4.7	$	320,882
Options exercisable—December 31, 2021		458		$	60.17		3.7	$	274,155

Summary of Activity Related to RSUs

The following table summarizes the activity related to RSUs for the year ended December 31, 2021:

	RSUs Outstanding
	Shares (in thousands)			Weighted- Average Grant Date Fair Value Per Share
Unvested and outstanding at January 1, 2021		1,561		$	153.91
Granted		632			513.94
Vested		(773	)		174.01
Canceled		(181	)		206.81
Unvested and outstanding at December 31, 2021		1,239		$	317.48

Schedule of Assumptions Used for Estimation of Fair Value of Employee Options

The fair value of employee options is estimated using the Black-Scholes option-pricing model with the following assumptions:
 

	Year Ended December 31,
	2021		2020		2019
Risk-free interest rate (%)	0.04-0.10		0.14-1.60		2.56
Expected term (years)		0.50		0.50		0.50
Volatility (%)	42.73-45.67		34.75-67.22		41.32-45.07
Expected dividends		—		—		—

Summary of Activity Related to Employee Stock Purchase Plan

The following table summarizes the activity related to ESPP:

	Shares Issued  (in thousands)		Weighted- Average Purchase Price		Total Cash Proceeds (in thousands)
2021		77	$	372.50	$	28,667
2020		132	$	149.23	$	19,653
2019		116	$	123.69	$	14,383