Mortgage Servicing Rights, net - Principle Balance by Category (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Mortgage Servicing Rights
Total	$ 720,361	$ 873,238
Custodial escrow balances maintained on serviced loans	9,583	7,688
FNMA
Mortgage Servicing Rights
Total	176,052	130,425
FHLB
Mortgage Servicing Rights
Total	72,416	86,778
Private investors
Mortgage Servicing Rights
Total	$ 471,893	$ 656,035