Indebtedness - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Debt Instrument [Line Items]
Interest Expense	$ 122	$ 111	$ 232	$ 217
Advance Facilities
Debt Instrument [Line Items]
Short-Term Debt, Weighted Average Interest Rate, over Time			7.40%	2.80%
Advance Facilities | Servicing
Debt Instrument [Line Items]
Short-Term Debt, Weighted Average Interest Rate, over Time	7.50%	3.10%
Warehouse & MSR Facilities
Debt Instrument [Line Items]
Short-Term Debt, Weighted Average Interest Rate, over Time	7.40%	3.10%	7.20%	2.60%
Debt
Debt Instrument [Line Items]
Interest Expense	$ 112	$ 90	$ 211	$ 176
Unsecured Senior Notes
Debt Instrument [Line Items]
Maximum percentage redeemable on unsecured debt			40.00%
Repayments of debt			$ 0	0
Amount of principal amount outstanding repaid			$ 0	$ 0