Deferred Revenue of Membership Upgrade Sales and Deferred Commission Expense - Schedule of Change in Deferred Revenue and Deferred Commissions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Movement in Deferred Revenue
Revenue recognized from membership upgrade sales upfront payments	$ (11,191)	$ (9,675)	$ (8,660)
Net increase in deferred revenue - upfront payments from membership grade sales	36,935	22,954	19,655
Movement in Deferred Costs
Deferred commission expense as of December 31	42,471	41,149
Deferred commission expense	8,657	4,995
Commission expense recognized	(3,779)	(3,673)
Net increase in deferred commission expense	4,878	1,322
Deferred commission expense as of December 31,	47,349	42,471	41,149
Membership Subscriptions
Movement in Deferred Revenue
Deferred revenue - upfront payments from membership upgrade sales as of December 31,	138,878	126,814
Membership upgrade sales current period, gross	36,270	21,739
Revenue recognized from membership upgrade sales upfront payments	(11,191)	(9,675)
Net increase in deferred revenue - upfront payments from membership grade sales	25,079	12,064
Deferred revenue - upfront payments from membership upgrade sales as of December 31,	$ 163,957	$ 138,878	$ 126,814