MARKETABLE SECURITIES (Details) - USD ($) |
Jun. 30, 2019 |
Dec. 31, 2018 |
|---|---|---|
| Fair Value [Member] | ||
| Certificates of deposit | $ 7,006,000 | $ 13,151,000 |
| Short term bond funds | 14,007,000 | 9,640,000 |
| Corporate bonds and notes | 11,103,000 | 8,437,000 |
| Total marketable securities | 32,116,000 | 31,228,000 |
| Cost Basis [Member] | ||
| Certificates of deposit | 6,998,000 | 13,151,000 |
| Short term bond funds | 13,970,000 | 9,648,000 |
| Corporate bonds and notes | 11,021,000 | 8,518,000 |
| Total marketable securities | 31,989,000 | 31,317,000 |
| Gross Unrealized Gains [Member] | ||
| Certificates of deposit | 8,000 | |
| Short term bond funds | 37,000 | |
| Corporate bonds and notes | 145,000 | |
| Total marketable securities | 190,000 | |
| Gross Unrealized Losses [Member] | ||
| Certificates of deposit | ||
| Short term bond funds | (8,000) | |
| Corporate bonds and notes | (63,000) | (81,000) |
| Total marketable securities | $ (63,000) | $ (89,000) |