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Note 1 - Significant Accounting Policies - Fair Value of the Company's Investments by Type (Details) $ in Thousands | Sep. 30, 2021 USD ($)
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Amortized Cost | $ 28,211
Accrued Interest | 25
Gross Unrealized Gains | 6
Gross Unrealized Losses | (3)
Estimated Fair Value | 28,239
US Government Agencies Debt Securities [Member] |
Amortized Cost | 24,986
Accrued Interest | 14
Gross Unrealized Gains | 3
Gross Unrealized Losses | (3)
Estimated Fair Value | 25,000
Certificates of Deposit [Member] |
Amortized Cost | 3,225
Accrued Interest | 11
Gross Unrealized Gains | 3
Gross Unrealized Losses | 0
Estimated Fair Value | $ 3,239

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