Revenue and Accounts Receivable, Net - Trade Receivables Associated with Significant Customers (Details) - Comcast Corporation - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2021	Dec. 31, 2020
Revenue, Major Customer [Line Items]
Accounts receivable, net	$ 21,517	$ 19,782
Trade accounts receivable \| Customer concentration risk
Revenue, Major Customer [Line Items]
Concentration risk percentage	15.40%	15.30%

The total amount due to the entity within one year of the balance sheet date (or one operating cycle, if longer) from outside sources, including trade accounts receivable, notes and loans receivable, as well as any other types of receivables, net of allowances established for the purpose of reducing such receivables to an amount that approximates their net realizable value.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant