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)		1,397,074
Issuance of common stock pursuant to exercise of stock options	7,667	$ 2	7,665
Issuance of common stock pursuant to settlement of restricted stock units (in shares)		562,755
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)		(160,964)
Common stock surrendered for employees' tax liability upon settlement of restricted stock units	(2,856)		(2,856)
Other comprehensive loss	26				26
Net loss	(73,023)			(73,023)
Ending balance (in shares) at Sep. 30, 2019		92,212,316
Ending balance at Sep. 30, 2019	327,721	$ 92	571,607	(244,004)	26
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	20,723		20,723
Beginning balance (in shares) at Jun. 30, 2019		91,777,537
Beginning balance at Jun. 30, 2019	312,245	$ 92	562,894	(250,785)	44
Increase (Decrease) in Stockholders' Equity
Issuance of common stock pursuant to exercise of stock options (in shares)		297,475
Issuance of common stock pursuant to exercise of stock options	1,897	$ 0	1,897
Issuance of common stock pursuant to settlement of restricted stock units (in shares)		195,840
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)		(58,536)
Common stock surrendered for employees' tax liability upon settlement of restricted stock units	(1,064)		(1,064)
Other comprehensive loss	(18)				(18)
Net loss	6,782			6,782
Ending balance (in shares) at Sep. 30, 2019		92,212,316
Ending balance at Sep. 30, 2019	327,721	$ 92	571,607	(244,004)	26
Increase (Decrease) in Stockholders' Equity
Stock Issued During Period, Shares, Employee Stock Purchase Plans		0
Stock Issued During Period, Value, Employee Stock Purchase Plan	0		0
APIC, Share-based Payment Arrangement, Increase for Cost Recognition	$ 7,880		7,880
Temporary equity, shares issued (in shares)	0
Temporary equity, shares outstanding (in shares)	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)	1,825,684	1,825,684
Issuance of common stock pursuant to exercise of stock options	$ 11,502	$ 2	11,500
Issuance of common stock pursuant to settlement of restricted stock units (in shares)		1,017,675
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)		(305,410)
Common stock surrendered for employees' tax liability upon settlement of restricted stock units	(10,987)		(10,987)
Other comprehensive loss	266				266
Net loss	$ (32,562)			(32,562)
Ending balance (in shares) at Sep. 30, 2020	100,241,416	100,241,416
Ending balance at Sep. 30, 2020	$ 400,279	$ 100	684,219	(284,348)	308
Increase (Decrease) in Stockholders' Equity
Temporary Equity, Stock Issued During Period, Value, New Issues	39,812
Stock Issued During Period, Shares, Employee Stock Purchase Plans		186,925
Stock Issued During Period, Value, Employee Stock Purchase Plan	3,436		3,436
Common Stock Dividends, Shares		30,640
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	$ 27,477		27,477
TemporaryEquityStockIssuedDuringPeriodSharesNewIssues	40,000
Temporary equity, shares outstanding (in shares)	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
Beginning balance (in shares) at Jun. 30, 2020		99,394,432
Beginning balance at Jun. 30, 2020	355,260	$ 99	673,234	(318,514)	441
Increase (Decrease) in Stockholders' Equity
Issuance of common stock pursuant to exercise of stock options (in shares)		567,854
Issuance of common stock pursuant to exercise of stock options	3,998	$ 1	3,997
Issuance of common stock pursuant to settlement of restricted stock units (in shares)		353,160
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)		(104,670)
Common stock surrendered for employees' tax liability upon settlement of restricted stock units	(4,922)		(4,922)
Other comprehensive loss	(133)				(133)
Net loss	$ 34,166			34,166
Ending balance (in shares) at Sep. 30, 2020	100,241,416	100,241,416
Ending balance at Sep. 30, 2020	$ 400,279	$ 100	684,219	$ (284,348)	$ 308
Increase (Decrease) in Stockholders' Equity
Temporary Equity, Stock Issued During Period, Value, New Issues	11
Stock Issued During Period, Shares, Employee Stock Purchase Plans		0
Stock Issued During Period, Value, Employee Stock Purchase Plan	0		0
Common Stock Dividends, Shares		30,640
Stock issued during period shares new issues (in shares)		0
Stock Issued During Period, Value, New Issues	0	$ 0	0
APIC, Share-based Payment Arrangement, Increase for Cost Recognition	$ 11,910		$ 11,910
TemporaryEquityStockIssuedDuringPeriodSharesNewIssues	0
Temporary equity, shares issued (in shares)	40,000
Temporary equity, shares outstanding (in shares)	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	$ 39,812