MARKETABLE SECURITIES (Details) - USD ($) |
Mar. 31, 2019 |
Dec. 31, 2018 |
|---|---|---|
| Fair Value [Member] | ||
| Certificates of deposit | $ 11,126,000 | $ 13,151,000 |
| Short term bond funds | 11,393,000 | 9,640,000 |
| Corporate bonds and notes | 8,318,000 | 8,437,000 |
| Total marketable securities | 30,837,000 | 31,228,000 |
| Cost Basis [Member] | ||
| Certificates of deposit | 11,126,000 | 13,151,000 |
| Short term bond funds | 11,379,000 | 9,648,000 |
| Corporate bonds and notes | 8,289,000 | 8,518,000 |
| Total marketable securities | 30,794,000 | 31,317,000 |
| Gross Unrealized Gains [Member] | ||
| Certificates of deposit | ||
| Short term bond funds | 14,000 | |
| Corporate bonds and notes | 86,000 | |
| Total marketable securities | 100,000 | |
| Gross Unrealized Losses [Member] | ||
| Certificates of deposit | ||
| Short term bond funds | (8,000) | |
| Corporate bonds and notes | (57,000) | (81,000) |
| Total marketable securities | $ (57,000) | $ (89,000) |