Indebtedness - Advance and Warehouse Facilities Summary (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Total advance, warehouse and MSR facilities, net	$ 4,302,000,000	$ 2,885,000,000
Advance, Warehouse and MSR Facilities
Debt Instrument [Line Items]
Outstanding	4,318,000,000	2,896,000,000
Collateral Pledged	8,781,000,000	7,262,000,000
Unamortized debt issuance costs	(16,000,000)	(11,000,000)
Total advance, warehouse and MSR facilities, net	$ 4,302,000,000	$ 2,885,000,000
Warehouse & MSR Facilities
Debt Instrument [Line Items]
Short-Term Debt, Weighted Average Interest Rate, over Time	7.60%	4.00%
Servicing | Advance Facilities
Debt Instrument [Line Items]
Short-Term Debt, Weighted Average Interest Rate, over Time	7.60%	4.10%
Loans Payable | Servicing | $350 Advance Facility Due October 2024 [Member] | Advance Facilities
Debt Instrument [Line Items]
Capacity Amount	$ 350,000,000
Outstanding	132,000,000	$ 150,000,000
Collateral Pledged	169,000,000	189,000,000
Loans Payable | Servicing | $300 Advance Facility Due November 2024 [Member] | Advance Financing, Internally Allocated
Debt Instrument [Line Items]
Capacity Amount	300,000,000
Outstanding	273,000,000	308,000,000
Collateral Pledged	364,000,000	410,000,000
Loans Payable | Servicing | $250 Advance Facility Due September 2025 [Member] | Advance Facilities
Debt Instrument [Line Items]
Capacity Amount	250,000,000
Outstanding	250,000,000	171,000,000
Collateral Pledged	326,000,000	209,000,000
Notes Payable to Banks | Servicing | Advance Facilities
Debt Instrument [Line Items]
Outstanding	682,000,000	669,000,000
Collateral Pledged	908,000,000	853,000,000
Notes Payable to Banks | Servicing | MSR Facilities
Debt Instrument [Line Items]
Outstanding	2,814,000,000	1,410,000,000
Collateral Pledged	6,958,000,000	5,499,000,000
Notes Payable to Banks | Servicing | $50 Advance facility due December 2024 [Member] | Advance Facilities
Debt Instrument [Line Items]
Capacity Amount	50,000,000
Outstanding	27,000,000	40,000,000
Collateral Pledged	49,000,000	45,000,000
Notes Payable to Banks | Servicing | $1500 MSR Warehouse Facility Due April 2025 [Member] | MSR Facilities
Debt Instrument [Line Items]
Capacity Amount	1,500,000,000
Outstanding	980,000,000	260,000,000
Collateral Pledged	1,455,000,000	2,284,000,000
Notes Payable to Banks | Servicing | $1450 MSR Warehouse Facility, Due November 2024 [Member] | MSR Financing, Internally Allocated
Debt Instrument [Line Items]
Capacity Amount	1,450,000,000
Outstanding	300,000,000	380,000,000
Collateral Pledged	2,164,000,000	927,000,000
Notes Payable to Banks | Servicing | $750 MSR Warehouse Facility, Due September 2025 [Member] | MSR Financing, Internally Allocated
Debt Instrument [Line Items]
Capacity Amount	750,000,000
Outstanding	545,000,000	380,000,000
Collateral Pledged	1,306,000,000	1,482,000,000
Notes Payable to Banks | Servicing | $500 MSR WH Facility due June 2025 [Member] | MSR Facilities
Debt Instrument [Line Items]
Capacity Amount	500,000,000
Outstanding	405,000,000	365,000,000
Collateral Pledged	655,000,000	732,000,000
Notes Payable to Banks | Servicing | $500 MSR Warehouse Facility due April 2025 [Member] | MSR Facilities
Debt Instrument [Line Items]
Capacity Amount	500,000,000
Outstanding	305,000,000	0
Collateral Pledged	634,000,000	0
Notes Payable to Banks | Servicing | $500 MSR Warehouse Facility Due June 2025 [Member] | MSR Facilities
Debt Instrument [Line Items]
Capacity Amount	500,000,000
Outstanding	250,000,000	0
Collateral Pledged	677,000,000	0
Notes Payable to Banks | Servicing | $50 MSR Warehouse Facility Due November 2024 [Member] | MSR Facilities
Debt Instrument [Line Items]
Capacity Amount	50,000,000
Outstanding	29,000,000	25,000,000
Collateral Pledged	67,000,000	74,000,000
Notes Payable to Banks | Servicing | $1750 warehouse facility [Member] | MSR Facilities
Debt Instrument [Line Items]
Capacity Amount	1,750,000,000
Notes Payable to Banks | Originations | Warehouse Facilities
Debt Instrument [Line Items]
Outstanding	822,000,000	817,000,000
Collateral Pledged	915,000,000	910,000,000
Notes Payable to Banks | Originations | $1500 Warehouse Facility Due June 2024 [Member] | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	1,500,000,000
Outstanding	107,000,000	206,000,000
Collateral Pledged	104,000,000	272,000,000
Notes Payable to Banks | Originations | $750 Warehouse Facility Due June 2024 [Member] | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	750,000,000
Outstanding	137,000,000	135,000,000
Collateral Pledged	176,000,000	133,000,000
Notes Payable to Banks | Originations | $750 Warehouse Facility Due October 2024 [Member] | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	750,000,000
Outstanding	155,000,000	202,000,000
Collateral Pledged	166,000,000	209,000,000
Notes Payable to Banks | Originations | $500 Warehouse Facility Due June 2024 [Member] | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	500,000,000
Outstanding	72,000,000	76,000,000
Collateral Pledged	78,000,000	80,000,000
Notes Payable to Banks | Originations | $350 Warehouse Facility Due August 2024 [Member] | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	350,000,000
Outstanding	73,000,000	31,000,000
Collateral Pledged	75,000,000	32,000,000
Notes Payable to Banks | Originations | $300 WH Facility Due February 2024 [Member] | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	300,000,000
Outstanding	0	115,000,000
Collateral Pledged	0	117,000,000
Notes Payable to Banks | Originations | $250 Million Warehouse Facility Due September 2025 [Member] | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	250,000,000
Outstanding	158,000,000	14,000,000
Collateral Pledged	177,000,000	17,000,000
Notes Payable to Banks | Originations | $200 Million Warehouse Facility Due December 2024 [Member] | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	200,000,000
Outstanding	82,000,000	18,000,000
Collateral Pledged	84,000,000	21,000,000
Notes Payable to Banks | Originations | $200 Million Warehouse Facility Due January 2025 [Member] | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	200,000,000
Outstanding	12,000,000	0
Collateral Pledged	21,000,000	0
Notes Payable to Banks | Originations | $100 Million Warehouse Facility Due April 2024 [Member] | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	100,000,000
Outstanding	25,000,000	19,000,000
Collateral Pledged	33,000,000	28,000,000
Notes Payable to Banks | Originations | $100 Million WH Facility Due April 2024 [Member] | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	100,000,000
Outstanding	0	0
Collateral Pledged	0	0
Notes Payable to Banks | Originations | $100 Warehouse Facility due December 2024 [Member] | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	100,000,000
Outstanding	1,000,000	1,000,000
Collateral Pledged	1,000,000	1,000,000
Notes Payable to Banks | Originations | $1 Warehouse Facility Due December 2024 [Member] | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	1,000,000
Outstanding	0	0
Collateral Pledged	0	$ 0
Notes Payable to Banks | Originations | $1000 Warehouse Facility [Member] | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	$ 1,000,000,000