Note 1 - Organization and Operations (Details Textual) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended
Aug. 02, 2017	Mar. 31, 2019	Dec. 31, 2018
Preferred Stock, Par or Stated Value Per Share		$ 0.001	$ 0.001
Cash, Cash Equivalents, and Short-term Investments, Total		$ 16,800
Retained Earnings (Accumulated Deficit), Ending Balance		$ (217,001)	$ (210,470)
Common Stock [Member]
Stock Issued During Period, Shares, Conversion of Convertible Securities		341,743
Series A Convertible Preferred Stock [Member]
Stock Issued During Period, Shares, New Issues	22,000
Preferred Stock, Par or Stated Value Per Share	$ 0.001	$ 0.001
Shares Issued, Price Per Share	$ 1,000
Proceeds from Issuance of Convertible Preferred Stock	$ 22,000
Conversion of Stock, Shares Converted		340

Cash includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the customer may deposit additional funds at any time and effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid Investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months. Short-term investments, exclusive of cash equivalents, generally consist of marketable securities intended to be sold within one year (or the normal operating cycle if longer) and may include trading securities, available-for-sale securities, or held-to-maturity securities (if maturing within one year), as applicable.

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The number of shares converted in a noncash (or part noncash) transaction. Noncash is defined as transactions during a period that do not result in cash receipts or cash payments in the period. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

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