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Investment Information - Net realized gains and losses (Details) - USD ($) $ in Thousands | 3 Months Ended
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Mar. 31, 2022 | Mar. 31, 2021
Available for sale securities: |  |  |
Available for sale securities, gross gains on investment sales |  | $ 19,707 | $ 65,002
Available for sale securities, gross losses on investment sales |  | (108,347) | (62,998)
Equity securities, at fair value: |  |  |
Net realized gains (losses) on sales during the period |  | 65,211 | 37,849
Net unrealized gains (losses) on equity securities still held at reporting date |  | (176,195) | 19,708
Allowance for credit losses: |  |  |
Allowance for credit losses - investments related |  | (31,722) | (1,648)
Allowance for credit losses - underwriting related |  | (4,286) | 5,268
Derivative instruments | [1] | (23,711) | 36,116
Other |  | (3,409) | (23,045)
Net realized gains (losses) |  | (292,414) | 142,461
Fixed maturities |  |  |
Available for sale securities: |  |  |
Change in fair value of assets and liabilities accounted for using the fair value option |  | (30,589) | 16,553
Other investments |  |  |
Available for sale securities: |  |  |
Change in fair value of assets and liabilities accounted for using the fair value option |  | 4,389 | 46,855
Equity securities |  |  |
Available for sale securities: |  |  |
Change in fair value of assets and liabilities accounted for using the fair value option |  | (3,313) | 2,065
Short-term investments |  |  |
Available for sale securities: |  |  |
Change in fair value of assets and liabilities accounted for using the fair value option |  | $ (149) | $ 736
[1] | See note 9 for information on the Company’s derivative instruments.

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