Note 6 - Fair Value Measurements and Financial Instruments - Assets Measured on a Recurring Basis (Details) - Fair Value, Recurring [Member] - USD ($) $ in Thousands |
Jun. 30, 2020 |
Dec. 31, 2019 |
---|---|---|
Assets, fair value | $ 79,780 | $ 95,960 |
Fair Value, Inputs, Level 1 [Member] | ||
Assets, fair value | 79,780 | 95,960 |
Bank Time Deposits [Member] | ||
Assets, fair value | 41,169 | 2,989 |
Bank Time Deposits [Member] | Fair Value, Inputs, Level 1 [Member] | ||
Assets, fair value | 41,169 | 2,989 |
Corporate Debt Securities [Member] | ||
Assets, fair value | 8,996 | 6,235 |
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member] | ||
Assets, fair value | 8,996 | 6,235 |
Canadian Provincial Promissory Notes [Member] | ||
Assets, fair value | 21,599 | 5,493 |
Canadian Provincial Promissory Notes [Member] | Fair Value, Inputs, Level 1 [Member] | ||
Assets, fair value | 21,599 | 5,493 |
Investments [Member] | ||
Assets, fair value | 8,016 | 81,243 |
Investments [Member] | Fair Value, Inputs, Level 1 [Member] | ||
Assets, fair value | $ 8,016 | $ 81,243 |