Non-consolidated VIEs - Corporation's VI in non-consolidated VIEs and max exposure to loss (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020
Variable Interest Entity
Assets	$ 74,189,163	$ 65,926,000	$ 65,910,369
Variable Interest Entity Not Primary Beneficiary
Variable Interest Entity
Assets	100,176	99,042
Maximum exposure to loss	100,176	99,042
Variable Interest Entity Not Primary Beneficiary | Servicing assets
Variable Interest Entity
Assets	91,209	90,273
Variable Interest Entity Not Primary Beneficiary | Mortgage servicing rights
Variable Interest Entity
Assets	91,209	90,273
Variable Interest Entity Not Primary Beneficiary | Other assets
Variable Interest Entity
Assets	8,967	8,769
Variable Interest Entity Not Primary Beneficiary | Servicing advances
Variable Interest Entity
Assets	$ 8,967	$ 8,769