Secured borrowings - Collateral Pledged (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Asset pledged as collateral without right
Collateral pledged
Total Loans, in consolidated VIEs, before allowance for loan losses	$ 3,317,635
Secured borrowings
Collateral pledged
Total Loans, in consolidated VIEs, before allowance for loan losses	3,317,635	$ 3,320,583
Borrowings under credit facilities and other financing arrangements | Loans and finance receivables
Collateral pledged
Total Loans, in consolidated VIEs, before allowance for loan losses	253,165	212,512
Borrowings under credit facilities and other financing arrangements | Asset pledged as collateral without right | Loans and finance receivables
Collateral pledged
Total Loans, in consolidated VIEs, before allowance for loan losses	253,165
Borrowings under repurchase agreements | Securities sold under agreements to repurchase
Collateral pledged
Total Loans, in consolidated VIEs, before allowance for loan losses	3,064,470	3,108,071
Borrowings under repurchase agreements | Asset pledged as collateral without right | Securities sold under agreements to repurchase
Collateral pledged
Total Loans, in consolidated VIEs, before allowance for loan losses	3,064,470
Real estate acquired in settlement of loans | Borrowings under repurchase agreements | Securities sold under agreements to repurchase
Collateral pledged
Total Loans, in consolidated VIEs, before allowance for loan losses	182,465	160,455
Loans, held for sale, at fair value | Borrowings under credit facilities and other financing arrangements | Loans and finance receivables
Collateral pledged
Total Loans, in consolidated VIEs, before allowance for loan losses	34,013	43,365
Loans, held for sale, at fair value | Borrowings under repurchase agreements | Securities sold under agreements to repurchase
Collateral pledged
Total Loans, in consolidated VIEs, before allowance for loan losses	402,434
Loans, net | Borrowings under credit facilities and other financing arrangements | Loans and finance receivables
Collateral pledged
Total Loans, in consolidated VIEs, before allowance for loan losses	219,152	169,147
Loans, net | Borrowings under repurchase agreements | Securities sold under agreements to repurchase
Collateral pledged
Total Loans, in consolidated VIEs, before allowance for loan losses	2,103,618	2,560,725
Loans, held at fair value
Collateral pledged
Total Loans, in consolidated VIEs, before allowance for loan losses		9,349
Mortgage backed securities | Borrowings under repurchase agreements | Securities sold under agreements to repurchase
Collateral pledged
Total Loans, in consolidated VIEs, before allowance for loan losses	20,972	20,770
Mortgage backed securities | Borrowings under repurchase agreements | Asset pledged as collateral without right | Securities sold under agreements to repurchase
Collateral pledged
Total Loans, in consolidated VIEs, before allowance for loan losses	375,953
Retained interest in assets of consolidated VIEs | Borrowings under repurchase agreements | Securities sold under agreements to repurchase
Collateral pledged
Total Loans, in consolidated VIEs, before allowance for loan losses	$ 354,981	$ 356,772