Revenue, Deferred Revenue and Remaining Performance Obligations - Revenue By Geographic Location (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Revenue	$ 176,991	$ 125,599	$ 174,886	$ 120,575
North America
Disaggregation of Revenue [Line Items]
Revenue	149,744	111,596	154,131	108,835
International
Disaggregation of Revenue [Line Items]
Revenue	$ 27,247	$ 14,003	$ 20,755	$ 11,740

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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+ Details