Secured Borrowings - Collateral Pledged (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Collateral pledged
Pledged Assets Carrying Value	$ 2,162,870	$ 1,668,460
Borrowings under credit facilities
Collateral pledged
Pledged Assets Carrying Value	613,793	561,257
Borrowings under repurchase agreements
Collateral pledged
Pledged Assets Carrying Value	1,549,077	1,107,203
Loans, net | Borrowings under credit facilities
Collateral pledged
Pledged Assets Carrying Value	492,646	436,738
Loans, net | Borrowings under repurchase agreements
Collateral pledged
Pledged Assets Carrying Value	1,201,100	721,887
Mortgage servicing rights | Borrowings under credit facilities
Collateral pledged
Pledged Assets Carrying Value	53,044	61,304
Purchased future receivables | Borrowings under credit facilities
Collateral pledged
Pledged Assets Carrying Value	49,150	43,265
Real estate, held for sale | Borrowings under credit facilities
Collateral pledged
Pledged Assets Carrying Value	18,953	19,950
Mortgage backed securities | Borrowings under repurchase agreements
Collateral pledged
Pledged Assets Carrying Value	74,439	113,436
Retained interest in assets of consolidated VIEs | Borrowings under repurchase agreements
Collateral pledged
Pledged Assets Carrying Value	$ 273,538	$ 271,880