CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	[1]	Common Stock	Additional Paid-in Capital	Additional Paid-in Capital Cumulative Effect, Period of Adoption, Adjustment	[1]	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Accumulated Deficit Cumulative Effect, Period of Adoption, Adjustment	[1]
Beginning balance (in shares) at Dec. 31, 2018				57,554,000
Beginning balance at Dec. 31, 2018	$ 131,275			$ 57	$ 731,306			$ (13)	$ (600,075)
Increase (Decrease) in Stockholders' Equity
Exercise of stock options (in shares)				1,422,000
Exercise of stock options	17,675			$ 1	17,674
Issuance of common stock for Employee Stock Purchase Plan (in shares)				327,000
Issuance of common stock for Employee Stock Purchase Plan	6,206			$ 1	6,205
Exercise of common stock warrants (in shares)				93,000
Exercise of common stock warrants	327			$ 0	327
Fair value of common stock warrants at time of exercise	5,492				5,492
Stock-based compensation expense	58,622				58,622
Unrealized gain (loss) on short-term investments, net of deferred tax	77							77
Foreign currency translation adjustments	58							58
Net income	(24,753)								(24,753)
Ending balance (in shares) at Dec. 31, 2019				59,396,000
Ending Balance at Dec. 31, 2019	$ 194,979			$ 59	819,626			122	(624,828)
Increase (Decrease) in Stockholders' Equity
Exercise of stock options (in shares)	2,339,467			2,341,000
Exercise of stock options	$ 57,750			$ 2	57,748
Issuance of common stock for Employee Stock Purchase Plan (in shares)				303,000
Issuance of common stock for Employee Stock Purchase Plan	9,116			$ 1	9,115
Exercise of common stock warrants (in shares)				295,000
Exercise of common stock warrants	2,950				2,950
Fair value of common stock warrants at time of exercise	26,335				26,335
Equity component of convertible senior notes issuance, net of issuance costs	85,803				85,803
Payment for capped call transactions related to convertible senior notes	(34,069)				(34,069)
Stock-based compensation expense	57,725				57,725
Unrealized gain (loss) on short-term investments, net of deferred tax	(20)							(20)
Foreign currency translation adjustments	118							118
Net income	(34,382)								(34,382)
Ending balance (in shares) at Dec. 31, 2020				62,335,000
Ending Balance at Dec. 31, 2020	$ 366,305	$ (76,754)		$ 62	1,025,233	$ (85,803)		220	(659,210)	$ 9,049
Increase (Decrease) in Stockholders' Equity
Accounting Standards Update [Extensible List]	Accounting Standards Update 2020-06
Exercise of stock options (in shares)	1,128,791			1,129,000
Exercise of stock options	$ 41,823			$ 2	41,821
Vesting of restricted stock units, net of shares withheld for taxes (in shares)				38,000
Vesting of restricted stock units, net of shares withheld for taxes	(1,551)				(1,551)
Issuance of common stock for Employee Stock Purchase Plan (in shares)				173,000
Issuance of common stock for Employee Stock Purchase Plan	11,069				11,069
Exercise of common stock warrants (in shares)				158,000
Exercise of common stock warrants	899				899
Fair value of common stock warrants at time of exercise	15,500				15,500
Stock-based compensation expense	61,091				61,091
Unrealized gain (loss) on short-term investments, net of deferred tax	(693)							(693)
Foreign currency translation adjustments	(143)							(143)
Net income	15,566								15,566
Ending balance (in shares) at Dec. 31, 2021				63,833,000
Ending Balance at Dec. 31, 2021	$ 433,112			$ 64	$ 1,068,259			$ (616)	$ (634,595)

[1] The Company adopted ASU No. 2020-06, Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity effective January 1, 2021 (see Note 2, “Summary of Significant Accounting Policies”).