Revenue - Fees Collected (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Revenue from fees, net	$ 801,275	$ 228,600	$ 159,847
Collection agency fees
Disaggregation of Revenue [Line Items]
Revenue from fees, net	4,473	2,777	2,111
Borrower fees
Disaggregation of Revenue [Line Items]
Revenue from fees, net	$ 7,289	$ 2,093	$ 1,539