Fair Value Measurements - Available For Sale (Details) - USD ($)
$ in Thousands
Dec. 31, 2021
Dec. 31, 2020
Fair value of available for sale marketable securities    
Amortized Cost $ 5,996 $ 27,800
Gross Unrealized Gains   5
Gross Unrealized Losses (3) (1)
Fair Value 5,993 27,804
U.S. Treasury securities    
Fair value of available for sale marketable securities    
Amortized Cost 1,012 6,074
Gross Unrealized Losses (2)  
Fair Value 1,010 6,074
U.S. Government agency securities    
Fair value of available for sale marketable securities    
Amortized Cost 4,984 21,726
Gross Unrealized Gains   5
Gross Unrealized Losses (1) (1)
Fair Value $ 4,983 $ 21,730