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Marketable Securities - Narrative (Details) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2021
Jun. 30, 2020
Investments, Debt and Equity Securities [Abstract]        
Marketable securities, realized gain $ 41 $ 14 $ 52 $ 290
Marketable securities, realized loss $ 39 $ 6 $ 107 $ 878