CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Accumulated Other Comprehensive Loss	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2020		45,804
Beginning balance at Dec. 31, 2020	$ 134,260	$ 510,061	$ 14	$ (375,815)
Increase (Decrease) in Shareholders' Equity
Net loss	(3,289)			(3,289)
Stock-based compensation expense	7,019	$ 7,019
Stock option exercises (in shares)		359
Stock option exercises	3,532	$ 3,532
Shares issued under the Employee Stock Purchase Plan (in shares)		14
Shares issued under the Employee Stock Purchase Plan	249	$ 249
Issuance of stock for restricted stock unit vesting (in shares)		76
Issuance of stock for restricted stock unit vesting	0
Restricted stock withheld for employee tax remittance (in shares)		(28)
Restricted stock withheld for employee tax remittance	(1,501)	$ (1,501)
Unrealized loss on investments	(61)		(61)
Ending balance (in shares) at Mar. 31, 2021		46,225
Ending balance at Mar. 31, 2021	140,209	$ 519,360	(47)	(379,104)
Beginning balance (in shares) at Dec. 31, 2021		46,880
Beginning balance at Dec. 31, 2021	170,462	$ 553,902	(154)	(383,286)
Increase (Decrease) in Shareholders' Equity
Net loss	(7,091)			(7,091)
Stock-based compensation expense	9,531	$ 9,531
Stock option exercises (in shares)		125
Stock option exercises	1,155	$ 1,155
Shares issued under the Employee Stock Purchase Plan (in shares)		9
Shares issued under the Employee Stock Purchase Plan	310	$ 310
Issuance of stock for restricted stock unit vesting (in shares)		108
Issuance of stock for restricted stock unit vesting	0
Restricted stock withheld for employee tax remittance (in shares)		(41)
Restricted stock withheld for employee tax remittance	(1,423)	$ (1,423)
Unrealized loss on investments	(459)		(459)
Ending balance (in shares) at Mar. 31, 2022		47,081
Ending balance at Mar. 31, 2022	$ 172,485	$ 563,475	$ (613)	$ (390,377)