CONSOLIDATED BALANCE SHEETS (Parentheticals) - $ / shares |
Mar. 31, 2019 |
Dec. 31, 2018 |
Dec. 31, 2017 |
|---|---|---|---|
| Statement of Financial Position [Abstract] | |||
| Preferred stock, shares authorized | 50,000 | 50,000 | 50,000 |
| Preferred stock, shares issued | 0 | 0 | 0 |
| Preferred stock, shares outstanding | 0 | 0 | 0 |
| Common stock, no par value (in dollars per share) | $ 0 | $ 0 | $ 0 |
| Common stock, shares authorized | 30,000,000 | 30,000,000 | 30,000,000 |
| Common stock, shares issued | 9,662,181 | 9,662,181 | 9,657,319 |
| Common stock, shares outstanding | 9,625,719 | 9,625,719 | 9,628,496 |
| Treasury stock, shares | 36,462 | 36,462 | 28,823 |