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Commitments (Details) - USD ($) | 12 Months Ended
--- | ---
Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Commitments |  |  |
Rent expense | $ 411,000 | $ 420,000 | $ 411,000
Maximum amount of loan | 79,500,000 |  |
Amount drawn and outstanding | 70,660,000 | $ 71,720,000 |
Office buildings and industrial properties |  |  |
Future minimum rental income: |  |  |
2019 | 169,471,000 |  |
2020 | 161,287,000 |  |
2021 | 142,712,000 |  |
2022 | 116,306,000 |  |
2023 | 97,853,000 |  |
Thereafter (2023-2036) | 269,863,000 |  |
Total | $ 957,492,000 |  |
Office buildings and industrial properties | Minimum |  |  |
Commitments |  |  |
Lease term | 1 year |  |
Corporate office space |  |  |
Commitments |  |  |
Extension period | 5 years |  |
Future minimum lease payments: |  |  |
2019 | $ 412,000 |  |
2020 | 421,000 |  |
2021 | 429,000 |  |
2022 | 438,000 |  |
2023 | 447,000 |  |
Thereafter | 340,000 |  |
Total | $ 2,487,000 |  |

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