Mortgage Servicing Rights and Related Liabilities - Fair Value Sensitivity Analysis (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Mortgage servicing rights
Excess Spread Financing - Hypothetical Sensitivities
Total prepayment speeds, 10% Adverse Change	$ (321)	$ (308)
Total prepayment speeds, 20% Adverse Change	(620)	(597)
Cost to Service per Loan, 10% Adverse Change	(78)	(84)
Cost to Service per Loan, 20% Adverse Change	(157)	(169)
Mortgage servicing rights | 100 bps Adverse Change
Excess Spread Financing - Hypothetical Sensitivities
Option Adjusted Spread	(456)	(470)
Mortgage servicing rights | 200 bps Adverse Change
Excess Spread Financing - Hypothetical Sensitivities
Option Adjusted Spread	(876)	(904)
Excess spread financing
Excess Spread Financing - Hypothetical Sensitivities
Total prepayment speeds, 10% Adverse Change	8	8
Total prepayment speeds, 20% Adverse Change	17	17
Excess spread financing | 100 bps Adverse Change
Excess Spread Financing - Hypothetical Sensitivities
Option Adjusted Spread	12	13
Excess spread financing | 200 bps Adverse Change
Excess Spread Financing - Hypothetical Sensitivities
Option Adjusted Spread	$ 25	$ 28