Variable interest entities and securitization activities - Consolidated VIE Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Assets
Cash and cash equivalents	$ 229,531	$ 138,975	$ 67,928
Restricted cash	51,569	47,697	$ 51,728
Loans, held for sale, at fair value	552,935	340,288
Other assets	172,098	89,503
Total Assets	9,534,031	5,372,095
Liabilities
Secured borrowings	2,517,600	1,294,243
Total Liabilities	8,245,072	4,537,887
Consolidated VIEs
Assets
Loans, net	4,081,848	2,472,807
Total Assets	4,145,564	2,518,743
Liabilities
Secured borrowings	3,214,303	1,905,749
Reportable Legal Entities | Consolidated VIEs
Assets
Cash and cash equivalents	9,041	20
Restricted cash	33,187	13,790
Loans, net	4,081,848	2,472,807
Real estate, held for sale		4,456
Other assets	21,488	27,670
Total Assets	4,145,564	2,518,743
Liabilities
Secured borrowings	3,214,303	1,905,749
Total Liabilities	$ 3,214,303	$ 1,905,749