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Revenue Recognition - Summary of Contract Balances (Details) - USD ($)
$ in Thousands
Sep. 30, 2021
Dec. 31, 2020
Revenue from Contract with Customer [Abstract]    
Accounts receivable $ 6,817 $ 12,398
Obligations for refunds 5,403 3,448
Deferred revenue – current 332,783 274,819
Deferred revenue – non-current $ 366,676 $ 254,481