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Contract Assets and Liabilities - Summary of Net Asset Position for Contracts in Process (Details) - USD ($)
$ in Thousands
Dec. 31, 2020
Dec. 31, 2019
Contractors [Abstract]    
Unbilled revenue $ 97,543 $ 126,087
Deferred revenue (155,570) (102,673)
Net asset position for contracts in process $ (58,027) $ 23,414