Mortgage Servicing Rights and Related Liabilities - Fair Value Sensitivity Analysis (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Mortgage servicing rights
Excess Spread Financing - Hypothetical Sensitivities
Total prepayment speeds, 10% Adverse Change	$ (220)	$ (219)
Total prepayment speeds, 20% Adverse Change	(427)	(425)
Cost to Service per Loan, 10% Adverse Change	(83)	(89)
Cost to Service per Loan, 20% Adverse Change	(167)	(178)
Mortgage servicing rights | 100 bps Adverse Change
Excess Spread Financing - Hypothetical Sensitivities
Option Adjusted Spread	(362)	(368)
Mortgage servicing rights | 200 bps Adverse Change
Excess Spread Financing - Hypothetical Sensitivities
Option Adjusted Spread	(697)	(706)
Excess spread financing
Excess Spread Financing - Hypothetical Sensitivities
Total prepayment speeds, 10% Adverse Change	10	10
Total prepayment speeds, 20% Adverse Change	19	20
Excess spread financing | 100 bps Adverse Change
Excess Spread Financing - Hypothetical Sensitivities
Option Adjusted Spread	15	16
Excess spread financing | 200 bps Adverse Change
Excess Spread Financing - Hypothetical Sensitivities
Option Adjusted Spread	$ 31	$ 32