Note 6 - Marketable Securities - Balance of Held-to-maturity Debt Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Due in one year or less	$ 48,272
Due after one year through five years	69,435
Total marketable securities	$ 117,707	$ 123,956

Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Carrying amount of debt securities accounted for as held-to-maturity, net of adjustments including, but not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized, and fair value hedge accounting adjustments, maturing in the next fiscal year through the fifth fiscal year following the latest fiscal year.

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