Summary of Significant Accounting Policies - Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Total revenue	$ 74,173	$ 41,324	$ 187,179	$ 107,291
Online
Disaggregation of Revenue [Line Items]
Total revenue	72,032	38,829	180,858	100,637
Wholesale
Disaggregation of Revenue [Line Items]
Total revenue	$ 2,141	$ 2,495	$ 6,321	$ 6,654