Note 2 - Summary of Significant Accounting Policies - Fair Value of Financial Assets (Details) - USD ($) |
Dec. 31, 2018 |
Dec. 31, 2017 |
|---|---|---|
| Assets: | ||
| Investment | $ 258,000 | $ 343,000 |
| Marketable Securities [Member] | ||
| Assets: | ||
| Investment | 258,000 | 343,000 |
| Marketable Securities [Member] | Fair Value, Inputs, Level 1 [Member] | ||
| Assets: | ||
| Investment | 258,000 | 343,000 |
| Marketable Securities [Member] | Fair Value, Inputs, Level 2 [Member] | ||
| Assets: | ||
| Investment | ||
| Marketable Securities [Member] | Fair Value, Inputs, Level 3 [Member] | ||
| Assets: | ||
| Investment |