Note 6 - Marketable Securities - Summary of Gross Unrealized Losses and Fair Values on Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Less than 12 months, Fair value	$ 12,974	$ 16,580
Less than 12 months, Gross unrealized loss	(110)	(192)
12 months or greater, Fair value	30,835	52,590
12 months or greater, Gross unrealized loss	$ (119)	$ (1,165)

This item represents the aggregate fair value of investments in debt and equity securities categorized neither as held-to-maturity nor trading securities that have been in a continuous unrealized loss position for less than twelve months.

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant