Indebtedness - Advance and Warehouse Facilities Summary (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Jan. 01, 2023
Debt Instrument [Line Items]
Total advance and warehouse facilities, net	$ 2,885,000,000	$ 4,997,000,000
Advance, Warehouse and MSR Facilities
Debt Instrument [Line Items]
Outstanding	2,896,000,000	5,009,000,000
Collateral Pledged	7,262,000,000	7,935,000,000
Unamortized debt issuance costs	(11,000,000)	(12,000,000)
Total advance and warehouse facilities, net	$ 2,885,000,000	$ 4,997,000,000
Warehouse & MSR Facilities
Debt Instrument [Line Items]
Short-Term Debt, Weighted Average Interest Rate, over Time	4.00%	2.00%
Servicing | Advance Facilities
Debt Instrument [Line Items]
Short-Term Debt, Weighted Average Interest Rate, over Time	4.10%	2.80%
Loans Payable | Servicing | $640 advance facility | Advance Facilities
Debt Instrument [Line Items]
Capacity Amount	$ 350,000,000
Outstanding	171,000,000	$ 160,000,000
Collateral Pledged	209,000,000	197,000,000
Loans Payable | Servicing | $640 advance facility | Advance Facilities | Subsequent Event
Debt Instrument [Line Items]
Capacity Amount			$ 250,000,000
Loans Payable | Servicing | $350 Advance Facility Due October 2024 | Advance Facilities
Debt Instrument [Line Items]
Capacity Amount	350,000,000
Outstanding	150,000,000	234,000,000
Collateral Pledged	189,000,000	318,000,000
Loans Payable | Servicing | $300 Advance Facility Due November 2024 | Advance Financing, Internally Allocated
Debt Instrument [Line Items]
Capacity Amount	350,000,000
Outstanding	308,000,000	162,000,000
Collateral Pledged	410,000,000	190,000,000
Notes Payable to Banks | Servicing | Advance Facilities
Debt Instrument [Line Items]
Outstanding	669,000,000	614,000,000
Collateral Pledged	853,000,000	794,000,000
Notes Payable to Banks | Servicing | MSR Facilities
Debt Instrument [Line Items]
Outstanding	1,410,000,000	270,000,000
Collateral Pledged	5,499,000,000	2,814,000,000
Notes Payable to Banks | Servicing | $260 warehouse facility | MSR Facilities
Debt Instrument [Line Items]
Capacity Amount	500,000,000
Outstanding	380,000,000	0
Collateral Pledged	1,482,000,000	745,000,000
Notes Payable to Banks | Servicing | $260 warehouse facility | MSR Financing, Internally Allocated
Debt Instrument [Line Items]
Capacity Amount	500,000,000
Notes Payable to Banks | Servicing | $150 warehouse facility | MSR Facilities
Debt Instrument [Line Items]
Capacity Amount	50,000,000
Outstanding	25,000,000	10,000,000
Collateral Pledged	74,000,000	124,000,000
Notes Payable to Banks | Servicing | $1200 warehouse facility | MSR Facilities
Debt Instrument [Line Items]
Capacity Amount	1,400,000,000
Notes Payable to Banks | Servicing | $400 Warehouse Facility Due August 2022 | MSR Facilities
Debt Instrument [Line Items]
Capacity Amount	1,050,000,000
Outstanding	260,000,000	260,000,000
Collateral Pledged	2,284,000,000	1,107,000,000
Notes Payable to Banks | Servicing | $400 Warehouse Facility Due August 2022 | MSR Financing, Internally Allocated
Debt Instrument [Line Items]
Capacity Amount	1,050,000,000
Notes Payable to Banks | Servicing | $400 Warehouse Facility, Due September 2023 | MSR Financing, Internally Allocated
Debt Instrument [Line Items]
Capacity Amount	600,000,000
Outstanding	380,000,000	0
Collateral Pledged	927,000,000	838,000,000
Notes Payable to Banks | Servicing | $75 Advance facility due December 2022 | Advance Facilities
Debt Instrument [Line Items]
Capacity Amount	75,000,000
Outstanding	40,000,000	58,000,000
Collateral Pledged	45,000,000	89,000,000
Notes Payable to Banks | Servicing | $400 Warehouse Facility Due June 2024 | MSR Facilities
Debt Instrument [Line Items]
Capacity Amount	500,000,000
Outstanding	365,000,000	0
Collateral Pledged	732,000,000	0
Notes Payable to Banks | Originations | Warehouse Facilities
Debt Instrument [Line Items]
Outstanding	817,000,000	4,125,000,000
Collateral Pledged	910,000,000	4,327,000,000
Notes Payable to Banks | Originations | $750 warehouse facility due October 2021 | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	0
Outstanding	0	256,000,000
Collateral Pledged	0	270,000,000
Notes Payable to Banks | Originations | $500 Million Warehouse Facility Due June 2023 | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	200,000,000
Outstanding	18,000,000	188,000,000
Collateral Pledged	21,000,000	194,000,000
Notes Payable to Banks | Originations | $500 Million Warehouse Facility Due September 2022 | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	450,000,000
Outstanding	0	87,000,000
Collateral Pledged	0	89,000,000
Notes Payable to Banks | Originations | $500 Million Warehouse Facility Due June 2022 | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	300,000,000
Outstanding	115,000,000	419,000,000
Collateral Pledged	117,000,000	430,000,000
Notes Payable to Banks | Originations | $500 Million Warehouse Facility Due August 2023 | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	250,000,000
Outstanding	0	5,000,000
Collateral Pledged	0	6,000,000
Notes Payable to Banks | Originations | $200 Warehouse Facility Due April 2022 | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	125,000,000
Outstanding	1,000,000	67,000,000
Collateral Pledged	1,000,000	67,000,000
Notes Payable to Banks | Originations | $30 Million Warehouse Facility, Due January 2022 | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	0
Outstanding	0	0
Collateral Pledged	0	0
Notes Payable to Banks | Originations | $2000 Warehouse Facility | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	1,000,000,000
Notes Payable to Banks | Originations | $300 warehouse facility | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	200,000,000
Outstanding	19,000,000	46,000,000
Collateral Pledged	28,000,000	58,000,000
Notes Payable to Banks | Originations | $1500 Warehouse Facility Due February 2023 | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	1,500,000,000
Outstanding	206,000,000	1,224,000,000
Collateral Pledged	272,000,000	1,341,000,000
Notes Payable to Banks | Originations | $1500 Warehouse Facility Due June 2023 | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	1,500,000,000
Outstanding	135,000,000	356,000,000
Collateral Pledged	133,000,000	345,000,000
Notes Payable to Banks | Originations | $1000 Warehouse Facility Due October 2023 | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	750,000,000
Outstanding	202,000,000	991,000,000
Collateral Pledged	209,000,000	1,024,000,000
Notes Payable to Banks | Originations | $500 Warehouse Facility Due September 2024 | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	500,000,000
Outstanding	14,000,000	409,000,000
Collateral Pledged	17,000,000	425,000,000
Notes Payable to Banks | Originations | $500 Million WH Facility Due June 2023 | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	500,000,000
Outstanding	76,000,000	39,000,000
Collateral Pledged	80,000,000	39,000,000
Notes Payable to Banks | Originations | $500 Million Warehouse Facility Due August 2023 | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	500,000,000
Outstanding	31,000,000	38,000,000
Collateral Pledged	$ 32,000,000	$ 39,000,000