Note 6 - Marketable Securities - Short-term and Long-term Marketable Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Amortized Cost	$ 108,552	$ 123,956
Unrealized Gains	27	16
Unrealized Losses	(261)	(497)
Fair Value	108,318	123,475
Bank Time Deposits [Member]
Amortized Cost	5,456	7,182
Unrealized Gains	1	12
Unrealized Losses	(25)	(22)
Fair Value	5,432	7,172
US States and Political Subdivisions Debt Securities [Member]
Amortized Cost	35,388	46,578
Unrealized Gains	23	1
Unrealized Losses	(43)	(187)
Fair Value	35,368	46,392
Corporate Debt Securities [Member]
Amortized Cost	29,841	38,490
Unrealized Gains	3	2
Unrealized Losses	(68)	(147)
Fair Value	29,776	38,345
US Government Agencies Debt Securities [Member]
Amortized Cost	37,866	31,706
Unrealized Gains		1
Unrealized Losses	(125)	(141)
Fair Value	$ 37,741	$ 31,566

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
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