Marketplace Revenue - Disaggregation of Revenue by Source (Details) - Transferred over Time - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disaggregation of Revenue [Line Items]
Net Revenue	$ 6,136	$ 4,499	$ 31,132	$ 142,356
Transaction fees
Disaggregation of Revenue [Line Items]
Net Revenue	3,374	3,874	25,776	140,117
Referral fees
Disaggregation of Revenue [Line Items]
Net Revenue	$ 2,762	$ 625	$ 5,356	$ 2,239