Note 1 - Significant Accounting Policies - Fair Value of the Company's Investments by Type (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Amortized Cost	$ 48,235	$ 41,407
Accrued Interest	169	77
Gross Unrealized Gains	4	11
Gross Unrealized Losses	(21)	(23)
Estimated Fair Value	48,387	41,472
US Government Agencies Debt Securities [Member]
Amortized Cost	27,897	20,266
Accrued Interest	96	34
Gross Unrealized Gains		2
Gross Unrealized Losses	(7)	(4)
Estimated Fair Value	27,986	20,298
Corporate Debt Securities [Member]
Amortized Cost	8,230	6,179
Accrued Interest	39	26
Gross Unrealized Gains		2
Gross Unrealized Losses	(8)	(8)
Estimated Fair Value	8,261	6,199
Certificates of Deposit [Member]
Amortized Cost	12,108	14,962
Accrued Interest	34	17
Gross Unrealized Gains	4	7
Gross Unrealized Losses	(6)	(11)
Estimated Fair Value	$ 12,140	$ 14,975

Represents available for sale securities accrued interest.

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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