Marketplace Revenue - Components of Marketplace Revenue (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]
Gain on sales of loans	$ 21,907	$ 7,739	$ 49,547		$ 23,724
Net fair value adjustments	2,705	(3,326)	(6,714)	[1]	(99,144)	[1]
Total marketplace revenue	174,556	54,635	408,018		175,993
Origination fees
Disaggregation of Revenue [Line Items]
Net Revenue	129,125	24,372	298,486		164,489
Servicing fees
Disaggregation of Revenue [Line Items]
Net Revenue	$ 20,819	$ 25,850	$ 66,699		$ 86,924

[1] Prior period amounts have been reclassified to conform to the current period presentation. See “Notes to Condensed Consolidated Financial Statements – Note 1. Summary of Significant Accounting Policies” for additional information.