Annual report pursuant to Section 13 and 15(d)

Fair Value Measurements - Summary of Values of Marketable Securities (Details)

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Fair Value Measurements - Summary of Values of Marketable Securities (Details) - Mutual Fund - USD ($)
$ in Thousands
Dec. 31, 2019
Dec. 31, 2018
Schedule Of Available For Sale Securities [Line Items]    
Marketable securities, Cost $ 5,129 $ 3,180
Marketable securities, Unrealized gains 1  
Marketable securities, Unrealized losses (6) (29)
Marketable securities, Fair value $ 5,124 $ 3,151