Note 6 - Marketable Securities (Details) - USD ($) $ in Thousands |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2015 |
Dec. 31, 2014 |
Dec. 31, 2013 |
|
| Disclosure Text Block Supplement [Abstract] | |||
| Investments, Fair Value Disclosure | $ 15,571 | $ 15,688 | |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 0 | 0 | |
| Available-for-sale Securities, Gross Realized Gain (Loss) | $ 2,402 | $ 5,712 | $ 334 |