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Investment Information - Net investment income (Details) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2021 | Jun. 30, 2020 | Jun. 30, 2021 | Jun. 30, 2020
Net investment income: |  |  |  |  |
Gross investment income |  | $ 135,176 | $ 151,965 | $ 261,142 | $ 320,291
Investment expenses |  | (23,563) | (20,480) | (50,673) | (43,653)
Net investment income |  | 111,613 | 131,485 | 210,469 | 276,638
Fixed maturities |  |  |  |  |
Net investment income: |  |  |  |  |
Gross investment income |  | 88,625 | 105,391 | 179,251 | 220,238
Term loans |  |  |  |  |
Net investment income: |  |  |  |  |
Gross investment income |  | 16,879 | 20,512 | 31,607 | 43,682
Equity securities |  |  |  |  |
Net investment income: |  |  |  |  |
Gross investment income |  | 8,584 | 6,219 | 14,234 | 12,226
Short-term investments |  |  |  |  |
Net investment income: |  |  |  |  |
Gross investment income |  | 1,138 | 3,383 | 1,745 | 8,279
Other |  |  |  |  |
Net investment income: |  |  |  |  |
Gross investment income | [1] | $ 19,950 | $ 16,460 | $ 34,305 | $ 35,866
[1] | Includes income distributions from investment funds and other items.

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