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Revenues - Contract Balances (Details) - USD ($)
$ in Thousands
6 Months Ended 12 Months Ended
Jun. 30, 2021
Dec. 31, 2020
Revenue, Contract Balances [Roll Forward]    
Beginning balance $ 2,796 $ 1,191
Services transferred to customers 2,753 3,934
Transfers to accounts receivable (2,822) (2,329)
Ending balance $ 2,727 $ 2,796