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Note 1 - Significant Accounting Policies - Scheduled Maturity for the Company's Investments (Details) - USD ($) $ in Thousands | Jun. 30, 2018 | Dec. 31, 2017
--- | --- | ---
Maturing in one year or less | $ 53,636 | $ 64,115
Maturing after one year through two years | 33,744 | 34,257
Maturing after two years |  | 7,038
Total investments | $ 87,380 | $ 105,410

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