Consolidated Statements Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Employee	Nonemployee	Common Stock	Additional Paid-in Capital	Additional Paid-in Capital Employee	Additional Paid-in Capital Nonemployee	Accumulated Deficit
Balance at beginning of period (in shares) at Dec. 31, 2018				54,065
Balance at beginning of period at Dec. 31, 2018	$ 56,306			$ 5	$ 386,775			$ (330,474)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)	1,045			1,466
Exercise of stock options	$ 7,099				7,099
Release of stock awards (in shares)				449
Employee stock-based compensation	6,943				6,943
Taxes paid related to net share settlement of equity awards (in shares)				(152)
Taxes paid related to net share settlement of equity awards	(2,850)				(2,850)
Issuance of common stock, net of issuance costs (in shares)				3,049
Issuance of common stock, net of issuance costs	49,877			$ 1	49,876
Short swing profit settlement	77				77
Net loss	(11,935)							(11,935)
Balance at end of period (in shares) at Dec. 31, 2019				58,877
Balance at end of period at Dec. 31, 2019	$ 105,517			$ 6	447,920			(342,409)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)	210			210
Exercise of stock options	$ 1,323				1,323
Release of stock awards (in shares)				370
Employee stock-based compensation		$ 7,622	$ 106			$ 7,622	$ 106
Taxes paid related to net share settlement of equity awards (in shares)				(103)
Taxes paid related to net share settlement of equity awards	(1,257)				(1,257)
Issuance of common stock, net of issuance costs (in shares)				4,929
Issuance of common stock, net of issuance costs	80,802				80,802
Net loss	(24,010)							(24,010)
Balance at end of period (in shares) at Dec. 31, 2020				64,283
Balance at end of period at Dec. 31, 2020	$ 170,103			$ 6	536,516			(366,419)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)	664			699
Exercise of stock options	$ 5,180				5,180
Release of stock awards (in shares)				181
Employee stock-based compensation		$ 11,346	$ 247			$ 11,346	$ 247
Taxes paid related to net share settlement of equity awards (in shares)				(54)
Taxes paid related to net share settlement of equity awards	(1,206)				(1,206)
Net loss	(21,279)							(21,279)
Balance at end of period (in shares) at Dec. 31, 2021				65,109
Balance at end of period at Dec. 31, 2021	$ 164,391			$ 6	$ 552,083			$ (387,698)