Note 12 - Net Loss Per Share - Anti-dilutive Securities (Details) - shares shares in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Anti-dilutive securities (in shares)	1,594	1,966
Share-based Payment Arrangement, Option [Member]
Anti-dilutive securities (in shares)	538	669
Restricted Stock Units (RSUs) [Member]
Anti-dilutive securities (in shares)	915	1,060
Employee Stock Purchase Plan [Member]
Anti-dilutive securities (in shares)	141	237

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://fasb.org/us-gaap/role/ref/legacyRef
-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