Commitments and Contingencies - Commitments to Extend Credit on Lines of Credit and to Purchase First Mortgages (Details) - Residential real estate - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	$ 3,347	$ 5,025
Home Equity Loans and Lines of Credit, Pledged Asset Lines and Other Lines of Credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commitments to extend credit related to unused HELOCs, PALs, and other lines of credit	2,996	4,533
First Mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commitments to purchase First Mortgage loans	$ 351	$ 492