Non-consolidated VIEs - Corporation's VI in non-consolidated VIEs and max exposure to loss (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022
Variable Interest Entity [Line Items]
Assets	$ 69,736,936	$ 67,637,917	$ 70,729,675
Variable Interest Entity Not Primary Beneficiary
Variable Interest Entity [Line Items]
Assets	100,303	105,771
Maximum exposure to loss	100,303	105,771
Variable Interest Entity Not Primary Beneficiary | Servicing assets
Variable Interest Entity [Line Items]
Assets	93,884	99,614
Variable Interest Entity Not Primary Beneficiary | Mortgage servicing rights
Variable Interest Entity [Line Items]
Assets	93,884	99,614
Variable Interest Entity Not Primary Beneficiary | Other assets
Variable Interest Entity [Line Items]
Assets	6,419	6,157
Variable Interest Entity Not Primary Beneficiary | Servicing advances
Variable Interest Entity [Line Items]
Assets	$ 6,419	$ 6,157