| Summary of marketable securities |
| | | | June 30, 2018 | | | | | | Amortized cost | | | Gross unrealized gain | | | Gross unrealized loss | | | Fair value | | | | | | | | | | | | | | | | | | | Matures within one year: | | | | | | | | | | | | | | | Corporate debentures | | $ | 10,191 | | | $ | 160 | | | $ | - | | | $ | 10,351 | | | | Government debentures | | | 284 | | | | 22 | | | | - | | | | 306 | | | | | | | 10,475 | | | | 182 | | | | - | | | | 10,657 | | | | | | | | | | | | | | | | | | | | | | | Matures after one year through three years: | | | | | | | | | | | | | | | | | | | Corporate debentures | | | 54,855 | | | | - | | | | (288 | ) | | | 54,567 | | | | Government debentures | | | 12,811 | | | | - | | | | (37 | ) | | | 12,774 | | | | | | | 67,666 | | | | - | | | | (325 | ) | | | 67,341 | | | | | | | | | | | | | | | | | | | | | | | Total | | $ | 78,141 | | | $ | 182 | | | $ | (325 | ) | | $ | 77,998 | |
| | | | December 31, 2017 | | | | | | Amortized cost | | | Gross unrealized gain | | | Gross unrealized loss | | | Fair value | | | | | | | | | | | | | | | | | | | Matures within one year: | | | | | | | | | | | | | | | Corporate debentures | | $ | 5,190 | | | $ | 41 | | | $ | - | | | $ | 5,231 | | | | Government debentures | | | 295 | | | | 11 | | | | - | | | | 306 | | | | | | | 5,485 | | | | 52 | | | | - | | | | 5,537 | | | | | | | | | | | | | | | | | | | | | | | Matures after one year through three years: | | | | | | | | | | | | | | | | | | | Corporate debentures | | | 56,514 | | | | - | | | | (65 | ) | | | 56,449 | | | | Government debentures | | | 12,403 | | | | - | | | | (17 | ) | | | 12,386 | | | | | | | 68,917 | | | | - | | | | (82 | ) | | | 68,835 | | | | | | | | | | | | | | | | | | | | | | | Total | | $ | 74,402 | | | $ | 52 | | | $ | (82 | ) | | $ | 74,372 | |
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