Consolidated Balance Sheets (Parentheticals) - $ / shares |
Dec. 31, 2019 |
Dec. 31, 2018 |
|---|---|---|
| Preferred stock, par value (in dollars per share) | $ 0.001 | $ 0.001 |
| Preferred stock, shares authorized (in shares) | 500,000,000 | 500,000,000 |
| Preferred stock, shares issued (in shares) | 0 | 0 |
| Preferred stock, shares outstanding (in shares) | 0 | 0 |
| Common stock, par value (in dollars per share) | $ 0.001 | $ 0.001 |
| Common stock, shares authorized (in shares) | 5,000,000,000 | 5,000,000,000 |
| Common stock, shares issued (in shares) | 390,449,879 | 390,449,879 |
| Treasury stock, shares (in shares) | 134,806,051 | 134,806,051 |