Equity Incentive Plans (Tables)

12 Months Ended

Dec. 31, 2021

Equity [Abstract]

Summary of Stock Option Plan Activity

The following table summarizes the stock option plan activity:

	Outstanding Options
				Weighted-
				Average
	Number of			Exercise
	Shares			Price
Balance at December 31, 2020		18,912,529		$	19.59
Granted		2,053,980		$	12.39
Exercised		(369,978	)	$	15.29
Cancelled		(1,652,594	)	$	21.69
Balance at December 31, 2021		18,943,937		$	18.71
	Outstanding RSUs
				Weighted-
				Average
	Number of			Grant Date
	Shares			Fair Value
Balance at December 31, 2020		602,741		$	15.84
Granted		2,448,957		$	10.86
Released		(154,487	)	$	15.98
Forfeited		(94,018	)	$	15.07
Balance at December 31, 2021		2,803,193		$	11.51

Schedule of Options Exercisable, Vested or Expected to Vest

	Years Ended December 31,
	2021				2020				2019
			Weighted-				Weighted-				Weighted-
			Average				Average				Average
			Exercise				Exercise				Exercise
	Options		Price		Options		Price		Options		Price
Exercisable at end of year		12,243,887	$	19.13		10,237,202	$	18.74		7,436,379	$	17.02
Options vested or expected to vest		18,416,243	$	18.77		18,179,553	$	19.58		15,962,432	$	20.31

Schedule of Exercise Prices And Weighted-average Remaining Contractual Lives For Options Outstanding

Exercise prices and weighted-average remaining contractual lives for the options outstanding as of December 31, 2021 were:

									Weighted-
			Weighted-						Average
			Average		Weighted-				Exercise
			Remaining		Average				Price of
Outstanding		Range of	Contractual		Exercise		Options		Options
Options		Exercise Prices	Life (in years)		Price		Exercisable		Exercisable
	2,697,794	$7.20–$10.55		5.28	$	9.09		1,598,055	$	8.17
	2,266,285	$10.64–$15.15		5.84		13.40		1,663,593		13.39
	3,307,235	$15.22-$15.72		8.54		15.71		1,035,174		15.70
	2,824,254	$15.75–$18.18		5.73		16.94		2,518,197		16.91
	3,045,374	$18.26–$24.97		6.56		23.04		2,276,351		23.17
	3,102,637	$25.02		7.76		25.02		1,619,032		25.02
	1,700,358	$25.06–$39.00		5.23		30.53		1,533,485		30.52
	18,943,937			6.59		18.71		12,243,887		19.13

Summary of Stock-Based Compensation Expense related to Stock-Based Payment Awards

The following table summarizes stock-based compensation expense related to stock-based payment awards pursuant to our equity compensation arrangements (in thousands):

	December 31,
	2021		2020		2019
Research and development	$	19,482	$	20,731	$	19,202
General and administrative		11,816		15,601		13,564
Sales and marketing		15,553		13,886		18,645
Total stock-based compensation expense	$	46,851	$	50,218	$	51,411

Summary of Fair Value of Option Grant and ESPP Purchase Right on Grant Date Using Black-Scholes Option Pricing Model

We estimated the fair value of each option grant and ESPP purchase right on the date of grant using the Black-Scholes option pricing model with the following weighted-average assumptions:

Options:

	December 31,
	2021			2020			2019
Risk-free interest rate		1.1	%		0.5	%		1.8	%
Dividend yield		—	%		—	%		—	%
Volatility		62.6	%		69.4	%		66.5	%
Expected life (years)		6			6			6

ESPP:

	December 31,
	2021			2020			2019
Risk-free interest rate		0.1	%		0.1	%		1.9	%
Dividend yield		—	%		—	%		—	%
Volatility		46.9	%		67.7	%		52.1	%
Expected life (months)		6			6			6