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Investments - Summary of Details on Realized and Unrealized Gains and Losses Related to Equity Securities (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]      
Unrealized gains and (losses) recognized during the reported period on equity securities still held at the end of the reporting period $ 25 $ 4,163 $ (17,169)