Consolidated Statements of Changes in Stockholders’ Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Income
Beginning balance (in shares) at Dec. 31, 2018		90,151,341
Beginning balance at Dec. 31, 2018	$ 371,938	$ 90	$ 542,829	$ (170,981)	$ 0
Increase (Decrease) in Stockholders' Equity
Issuance of common stock pursuant to exercise of stock options (in shares)		1,099,599
Issuance of common stock pursuant to exercise of stock options	5,770	$ 2	5,768
Issuance of common stock pursuant to settlement of restricted stock units (in shares)		366,915
Issuance of common stock pursuant to settlement of restricted stock units	0
Common stock surrendered for employees' tax liability upon settlement of restricted stock units (in shares)		(102,428)
Common stock surrendered for employees' tax liability upon settlement of restricted stock units	(1,792)		(1,792)
Other comprehensive income	44				44
Net loss	(79,804)			(79,804)
Ending balance (in shares) at Jun. 30, 2019		91,777,537
Ending balance at Jun. 30, 2019	312,245	$ 92	562,894	(250,785)	44
Increase (Decrease) in Stockholders' Equity
Stock Issued During Period, Shares, Employee Stock Purchase Plans		262,110
Stock Issued During Period, Value, Employee Stock Purchase Plan	3,246		3,246
APIC, Share-based Payment Arrangement, Increase for Cost Recognition	12,843		12,843
Beginning balance (in shares) at Mar. 31, 2019		90,926,249
Beginning balance at Mar. 31, 2019	314,349	$ 91	552,418	(238,160)	1
Increase (Decrease) in Stockholders' Equity
Issuance of common stock pursuant to exercise of stock options (in shares)		420,104
Issuance of common stock pursuant to exercise of stock options	2,039	$ 1	2,038
Issuance of common stock pursuant to settlement of restricted stock units (in shares)		227,026
Issuance of common stock pursuant to settlement of restricted stock units	0
Common stock surrendered for employees' tax liability upon settlement of restricted stock units (in shares)		(57,952)
Common stock surrendered for employees' tax liability upon settlement of restricted stock units	(975)		(975)
Other comprehensive income	43				43
Net loss	(12,625)			(12,625)
Ending balance (in shares) at Jun. 30, 2019		91,777,537
Ending balance at Jun. 30, 2019	312,245	$ 92	562,894	(250,785)	44
Increase (Decrease) in Stockholders' Equity
Stock Issued During Period, Shares, Employee Stock Purchase Plans		262,110
Stock Issued During Period, Value, Employee Stock Purchase Plan	3,246		3,246
APIC, Share-based Payment Arrangement, Increase for Cost Recognition	$ 6,167		6,167
Temporary Equity, Shares Issued	0
Temporary Equity, Shares Outstanding	0
Series A convertible preferred stock—par value $0.001 per share; 10,000,000 shares authorized; 40,000 and no shares issued and outstanding, respectively	$ 0
Beginning balance (in shares) at Dec. 31, 2019	93,001,597	93,001,597
Beginning balance at Dec. 31, 2019	$ 331,446	$ 93	583,097	(251,786)	42
Increase (Decrease) in Stockholders' Equity
Issuance of common stock pursuant to exercise of stock options (in shares)	1,257,830	1,257,830
Issuance of common stock pursuant to exercise of stock options	$ 7,504	$ 1	7,503
Issuance of common stock pursuant to settlement of restricted stock units (in shares)		664,515
Issuance of common stock pursuant to settlement of restricted stock units	0	$ 1	(1)
Common stock surrendered for employees' tax liability upon settlement of restricted stock units (in shares)		(200,740)
Common stock surrendered for employees' tax liability upon settlement of restricted stock units	(6,065)		(6,065)
Other comprehensive income	399				399
Net loss	$ (66,728)			(66,728)
Ending balance (in shares) at Jun. 30, 2020	99,394,432	99,394,432
Ending balance at Jun. 30, 2020	$ 355,260	$ 99	673,234	(318,514)	441
Increase (Decrease) in Stockholders' Equity
Temporary Equity, Stock Issued During Period, Value, New Issues	39,801
Stock Issued During Period, Shares, Employee Stock Purchase Plans		186,925
Stock Issued During Period, Value, Employee Stock Purchase Plan	3,436		3,436
Stock issued during period shares new issues (in shares)		4,484,305
Stock Issued During Period, Value, New Issues	69,701	$ 4	69,697
APIC, Share-based Payment Arrangement, Increase for Cost Recognition	$ 15,567		15,567
TemporaryEquityStockIssuedDuringPeriodSharesNewIssues	40,000
Beginning balance (in shares) at Mar. 31, 2020		93,957,774
Beginning balance at Mar. 31, 2020	$ 280,186	$ 94	591,420	(311,903)	575
Increase (Decrease) in Stockholders' Equity
Issuance of common stock pursuant to exercise of stock options (in shares)		519,432
Issuance of common stock pursuant to exercise of stock options	3,589	$ 1	3,588
Issuance of common stock pursuant to settlement of restricted stock units (in shares)		344,075
Issuance of common stock pursuant to settlement of restricted stock units	0
Common stock surrendered for employees' tax liability upon settlement of restricted stock units (in shares)		(98,079)
Common stock surrendered for employees' tax liability upon settlement of restricted stock units	(2,758)		(2,758)
Other comprehensive income	(134)				(134)
Net loss	$ (6,611)			(6,611)
Ending balance (in shares) at Jun. 30, 2020	99,394,432	99,394,432
Ending balance at Jun. 30, 2020	$ 355,260	$ 99	673,234	$ (318,514)	$ 441
Increase (Decrease) in Stockholders' Equity
Temporary Equity, Stock Issued During Period, Value, New Issues	39,801
Stock Issued During Period, Shares, Employee Stock Purchase Plans		186,925
Stock Issued During Period, Value, Employee Stock Purchase Plan	3,436		3,436
Stock issued during period shares new issues (in shares)		4,484,305
Stock Issued During Period, Value, New Issues	69,701	$ 4	69,697
APIC, Share-based Payment Arrangement, Increase for Cost Recognition	$ 7,851		$ 7,851
TemporaryEquityStockIssuedDuringPeriodSharesNewIssues	40,000
Temporary Equity, Shares Issued	40,000
Temporary Equity, Shares Outstanding	40,000
Series A convertible preferred stock—par value $0.001 per share; 10,000,000 shares authorized; 40,000 and no shares issued and outstanding, respectively	$ 39,801