Indebtedness - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Debt Instrument [Line Items]
Interest Expense	$ 146	$ 104	$ 378	$ 321
Advance Facilities
Debt Instrument [Line Items]
Short-Term Debt, Weighted Average Interest Rate, over Time			7.60%	3.40%
Advance Facilities | Servicing
Debt Instrument [Line Items]
Short-Term Debt, Weighted Average Interest Rate, over Time	7.80%	4.50%
Warehouse & MSR Facilities
Debt Instrument [Line Items]
Short-Term Debt, Weighted Average Interest Rate, over Time	7.80%	4.60%	7.40%	3.30%
Debt
Debt Instrument [Line Items]
Interest Expense	$ 131	$ 90	$ 342	$ 266
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