Equity Incentive Plans (Tables)

3 Months Ended

Mar. 31, 2020

Summary of Stock-Based Compensation Expense Related to Equity Incentive Rewards

The Company recognized total stock-based compensation cost related to equity incentive awards as follows (in thousands):

	For the Three Months Ended March 31,
	2020		2019
Stock-based compensation cost:
Stock options	$	3,849	$	3,917
Restricted stock units		4,933		1,698
Employee stock purchase plan		967		956
Total stock-based compensation cost	$	9,749	$	6,571

Summary of Stock Option Activity

Stock Options

The following table summarizes stock option activity for the Company’s stock-based compensation plans for the three months ended March 31, 2020:

						Weighted
				Weighted		Average		Aggregate
				Average		Remaining		Intrinsic
				Exercise		Contractual		Value
	Shares			Price		Life (Years)		(in thousands)
Options outstanding as of January 1, 2020		5,884,742		$	20.09		7.22	$	312,838
Options granted		211,243			68.61
Options exercised		(532,848	)		14.88
Options cancelled or expired		(79,246	)		15.77
Options outstanding as of March 31, 2020		5,483,891			22.53		7.11		285,564
Options exercisable as of March 31, 2020		2,997,298		$	15.35		6.21	$	177,582

Summary of Options Outstanding and Vested by Range of Exercise Prices

A summary of options outstanding and vested as of March 31, 2020 is as follows:

	Options Outstanding				Options Vested and Exercisable
Exercise	Number		Weighted Average		Number Vested		Weighted Average
Prices	Outstanding		Life (in Years)		and Exercisable		Life (in Years)
$1.50 to $1.90		29,963		1.1		29,963		1.1
2.86 to 6.40		152,780		2.9		152,780		2.9
8.04 to 11.72		457,714		3.9		457,714		3.9
12.20 to 15.06		1,933,421		6.4		1,517,566		6.2
16.06 to 24.00		1,581,078		7.9		555,420		7.8
31.99 to 42.21		826,351		8.7		235,511		8.7
55.10 to 86.61		502,584		9.5		48,344		9.0
		5,483,891				2,997,298

Summary of Fair Value Estimated Using Black-Scholes Option Pricing Model Assumptions

For the options granted during the periods presented, the fair value of options was estimated using the Black-Scholes option-pricing model with the following assumptions:

	For the Three Months Ended March 31,
	2020	2019
Fair market value of common stock	$67.27 - 86.61	$39.76 - 55.79
Volatility	43%	40%
Expected term	6 years	6 years
Expected dividend yield	n/a	n/a
Risk-free interest rate	0.82% - 1.25%	2.31% - 2.65%

Summary of RSU Activity

The following table summarizes RSU activity for the Company’s stock-based compensation plans for the three months ended March 31, 2020:

				Weighted
				Average
				Grant Date Fair
	Restricted Stock Units			Value Per Share
RSUs outstanding as of January 1, 2020		1,508,281		$	51.52
RSUs granted		945,698			68.89
RSUs vested		(186,475	)		43.89
RSUs cancelled		(56,280	)		49.45
RSUs outstanding as of March 31, 2020		2,211,224		$	59.64

2018 Employee Stock Purchase Plan

Summary of Fair Value Estimated Using Black-Scholes Option Pricing Model Assumptions

	For the Three Months Ended March 31,
	2020	2019
Fair market value of common stock	$85.14	$40.60
Volatility	32%	40%
Expected term	0.5 years	0.5 years
Expected dividend yield	n/a	n/a
Risk-free interest rate	1.54%	2.59%