Indebtedness - Advance and Warehouse Facilities Summary (Details) - USD ($)	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Debt Instrument [Line Items]
Total advance, warehouse and MSR facilities, net	$ 6,495,000,000	$ 4,302,000,000
Advance, Warehouse and MSR Facilities
Debt Instrument [Line Items]
Outstanding	6,515,000,000	4,318,000,000
Collateral Pledged	14,016,000,000	8,781,000,000
Unamortized debt issuance costs	(20,000,000)	(16,000,000)
Total advance, warehouse and MSR facilities, net	$ 6,495,000,000	$ 4,302,000,000
Warehouse & MSR Facilities
Debt Instrument [Line Items]
Short-Term Debt, Weighted Average Interest Rate, over Time	7.60%	7.60%
Servicing | Advance Facilities
Debt Instrument [Line Items]
Short-Term Debt, Weighted Average Interest Rate, over Time	7.50%	7.60%
Loans Payable | Servicing | $350 Advance Facility Due October 2026 [Member] | Advance Facilities
Debt Instrument [Line Items]
Capacity Amount	$ 350,000,000
Outstanding	119,000,000	$ 132,000,000
Collateral Pledged	151,000,000	169,000,000
Loans Payable | Servicing | $300 Advance Facility Due November 2024 [Member] | Advance Financing, Internally Allocated
Debt Instrument [Line Items]
Capacity Amount	300,000,000
Outstanding	0	273,000,000
Collateral Pledged	0	364,000,000
Loans Payable | Servicing | $500 Advance Facility Due August 2026 [Member] | Advance Facilities
Debt Instrument [Line Items]
Capacity Amount	500,000,000
Outstanding	423,000,000	250,000,000
Collateral Pledged	475,000,000	326,000,000
Loans Payable | Servicing | $500 Advance Facility Due July 2026 [Member] | Advance Facilities
Debt Instrument [Line Items]
Capacity Amount	500,000,000
Outstanding	285,000,000	0
Collateral Pledged	394,000,000	0
Loans Payable | Servicing | $500 Advance Facility Due July 2026 [Member] | Advance Financing, Internally Allocated
Debt Instrument [Line Items]
Capacity Amount	500,000,000
Notes Payable to Banks | Servicing | Advance Facilities
Debt Instrument [Line Items]
Outstanding	849,000,000	682,000,000
Collateral Pledged	1,060,000,000	908,000,000
Notes Payable to Banks | Servicing | MSR Facilities
Debt Instrument [Line Items]
Outstanding	3,650,000,000	2,814,000,000
Collateral Pledged	10,788,000,000	6,958,000,000
Notes Payable to Banks | Servicing | $50 Advance facility due July 2025 [Member] | Advance Facilities
Debt Instrument [Line Items]
Capacity Amount	50,000,000
Notes Payable to Banks | Servicing | $50 Advance facility due July 2025 [Member] | Advance Financing, Internally Allocated
Debt Instrument [Line Items]
Capacity Amount	50,000,000
Outstanding	22,000,000	27,000,000
Collateral Pledged	40,000,000	49,000,000
Notes Payable to Banks | Servicing | $1750 MSR Warehouse Facility Due April 2026 [Member] | MSR Facilities
Debt Instrument [Line Items]
Capacity Amount	1,750,000,000
Outstanding	950,000,000	980,000,000
Collateral Pledged	2,669,000,000	1,455,000,000
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	0	300,000,000
Collateral Pledged	0	2,164,000,000
Notes Payable to Banks | Servicing | $950 MSR Warehouse Facility, Due September 2026 [Member] | MSR Financing, Internally Allocated
Debt Instrument [Line Items]
Capacity Amount	950,000,000
Outstanding	550,000,000	545,000,000
Collateral Pledged	1,711,000,000	1,306,000,000
Notes Payable to Banks | Servicing | $750 MSR WH Facility due July 2026 [Member] | MSR Facilities
Debt Instrument [Line Items]
Capacity Amount	750,000,000
Outstanding	670,000,000	405,000,000
Collateral Pledged	1,066,000,000	655,000,000
Notes Payable to Banks | Servicing | $500 MSR Warehouse Facility due April 2026 [Member] | MSR Facilities
Debt Instrument [Line Items]
Capacity Amount	500,000,000
Outstanding	250,000,000	305,000,000
Collateral Pledged	781,000,000	634,000,000
Notes Payable to Banks | Servicing | $500 MSR Warehouse Facility Due June 2026 [Member] | MSR Facilities
Debt Instrument [Line Items]
Capacity Amount	500,000,000
Outstanding	150,000,000	250,000,000
Collateral Pledged	726,000,000	677,000,000
Notes Payable to Banks | Servicing | $50 MSR Warehouse Facility Due November 2025 [Member] | MSR Facilities
Debt Instrument [Line Items]
Capacity Amount	50,000,000
Outstanding	25,000,000	29,000,000
Collateral Pledged	80,000,000	67,000,000
Notes Payable to Banks | Servicing | $2000 warehouse facility [Member] | MSR Facilities
Debt Instrument [Line Items]
Capacity Amount	2,000,000,000
Notes Payable to Banks | Servicing | $1500 million MSR facility due July 2026 [Member] | MSR Facilities
Debt Instrument [Line Items]
Capacity Amount	1,500,000,000
Outstanding	475,000,000	0
Collateral Pledged	2,607,000,000	0
Notes Payable to Banks | Servicing | $1500 million MSR facility due July 2026 [Member] | MSR Financing, Internally Allocated
Debt Instrument [Line Items]
Capacity Amount	1,500,000,000
Notes Payable to Banks | Servicing | $500 MSR WH Facility due June 2026 [Member] | MSR Facilities
Debt Instrument [Line Items]
Capacity Amount	500,000,000
Outstanding	250,000,000	0
Collateral Pledged	519,000,000	0
Notes Payable to Banks | Servicing | $500 MSR Warehouse Facility due July 2026 [Member] | MSR Facilities
Debt Instrument [Line Items]
Capacity Amount	500,000,000
Outstanding	330,000,000	0
Collateral Pledged	629,000,000	0
Notes Payable to Banks | Originations | Warehouse Facilities
Debt Instrument [Line Items]
Outstanding	2,016,000,000	822,000,000
Collateral Pledged	2,168,000,000	915,000,000
Notes Payable to Banks | Originations | $1500 Warehouse Facility Due June 2025 [Member] | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	1,500,000,000
Outstanding	68,000,000	107,000,000
Collateral Pledged	71,000,000	104,000,000
Notes Payable to Banks | Originations | $750 Warehouse Facility Due February 2025 [Member] | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	750,000,000
Outstanding	112,000,000	137,000,000
Collateral Pledged	140,000,000	176,000,000
Notes Payable to Banks | Originations | $750 Warehouse Facility Due October 2025 [Member] | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	750,000,000
Outstanding	489,000,000	155,000,000
Collateral Pledged	530,000,000	166,000,000
Notes Payable to Banks | Originations | $500 Warehouse Facility Due June 2025 [Member] | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	500,000,000
Outstanding	90,000,000	72,000,000
Collateral Pledged	99,000,000	78,000,000
Notes Payable to Banks | Originations | $600 Warehouse Facility Due August 2025 [Member] | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	600,000,000
Outstanding	368,000,000	73,000,000
Collateral Pledged	381,000,000	75,000,000
Notes Payable to Banks | Originations | $1200 Million Warehouse Facility Due September 2026 [Member] | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	1,200,000,000
Outstanding	131,000,000	158,000,000
Collateral Pledged	148,000,000	177,000,000
Notes Payable to Banks | Originations | $200 Million Warehouse Facility Due December 2026 [Member] | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	200,000,000
Outstanding	112,000,000	82,000,000
Collateral Pledged	123,000,000	84,000,000
Notes Payable to Banks | Originations | $200 Million Warehouse Facility Due July 2025 [Member] | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	200,000,000
Outstanding	0	12,000,000
Collateral Pledged	0	21,000,000
Notes Payable to Banks | Originations | $100 Million Warehouse Facility Due April 2025 [Member] | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	100,000,000
Outstanding	56,000,000	25,000,000
Collateral Pledged	62,000,000	33,000,000
Notes Payable to Banks | Originations | $100 Million WH Facility Due April 2025 [Member] | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	100,000,000
Outstanding	0	0
Collateral Pledged	0	0
Notes Payable to Banks | Originations | $200 Warehouse Facility due July 2025 [Member] | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	200,000,000
Outstanding	105,000,000	1,000,000
Collateral Pledged	105,000,000	1,000,000
Notes Payable to Banks | Originations | $1 Warehouse Facility Due December 2025 [Member] | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	1,000,000
Outstanding	0	0
Collateral Pledged	0	0
Notes Payable to Banks | Originations | $1200 Warehouse Facility [Member] | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	1,200,000,000
Notes Payable to Banks | Originations | $500 Warehouse Facility Due November 2025 [Member] | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	500,000,000
Outstanding	247,000,000	0
Collateral Pledged	256,000,000	0
Notes Payable to Banks | Originations | $250 Warehouse Facility Due November 2025 [Member] | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	250,000,000
Outstanding	238,000,000	0
Collateral Pledged	$ 253,000,000	$ 0