Non-consolidated VIEs - Corporation's VI in non-consolidated VIEs and max exposure to loss (Details) - USD ($)	Sep. 30, 2024	Dec. 31, 2023	Sep. 30, 2023
Variable Interest Entity [Line Items]
Assets	$ 71,323,074,000	$ 70,758,155,000	$ 69,736,936,000
Variable Interest Entity Not Primary Beneficiary
Variable Interest Entity [Line Items]
Assets	92,267,000	99,290,000
Maximum exposure to loss	92,267,000	99,290,000
Variable Interest Entity Not Primary Beneficiary | Servicing assets
Variable Interest Entity [Line Items]
Assets	85,146,000	92,999,000
Variable Interest Entity Not Primary Beneficiary | Mortgage servicing rights
Variable Interest Entity [Line Items]
Assets	85,146,000	92,999,000
Variable Interest Entity Not Primary Beneficiary | Other assets
Variable Interest Entity [Line Items]
Assets	7,121,000	6,291,000
Variable Interest Entity Not Primary Beneficiary | Servicing advances
Variable Interest Entity [Line Items]
Assets	$ 7,121,000	$ 6,291,000