Note 7 - Fair Value of Financial Instruments - Assets and Liabilities Measured at Fair Value (Details) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Assets:
Cash and cash equivalents	$ 638	$ 1,815
Total Assets	778	2,040
Certificates of Deposit [Member]
Assets:
Certificate of deposit	140	225
Fair Value, Inputs, Level 1 [Member]
Assets:
Cash and cash equivalents	638	1,815
Total Assets	778	2,040
Fair Value, Inputs, Level 1 [Member] | Certificates of Deposit [Member]
Assets:
Certificate of deposit	140	225
Fair Value, Inputs, Level 2 [Member]
Assets:
Cash and cash equivalents
Total Assets
Fair Value, Inputs, Level 2 [Member] | Certificates of Deposit [Member]
Assets:
Certificate of deposit
Fair Value, Inputs, Level 3 [Member]
Assets:
Cash and cash equivalents
Total Assets
Fair Value, Inputs, Level 3 [Member] | Certificates of Deposit [Member]
Assets:
Certificate of deposit