Note 10 - NET LOSS PER SHARE - Anti-dilutive Securities (Details) - shares shares in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Anti-dilutive securities (in shares)	1,165	1,183	1,253	1,200
Share-based Payment Arrangement, Option [Member]
Anti-dilutive securities (in shares)	194	376	209	388
Restricted Stock Units (RSUs) [Member]
Anti-dilutive securities (in shares)	970	659	1,038	687
Employee Stock Purchase Plan [Member]
Anti-dilutive securities (in shares)	1	148	6	125

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

Name:	us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration