Indebtedness - Advance and Warehouse Facilities Summary (Details) - USD ($)	Oct. 01, 2023	Sep. 30, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Advance, warehouse and MSR facilities, net		$ 3,545,000,000	$ 2,885,000,000
Advance Facilities | Servicing | Loans payable | $350 advance facility
Debt Instrument [Line Items]
Capacity Amount		350,000,000
Outstanding		129,000,000	150,000,000
Collateral Pledged		166,000,000	189,000,000
Advance Facilities | Servicing | Loans payable | $250 advance facility(1)
Debt Instrument [Line Items]
Capacity Amount		250,000,000
Outstanding		207,000,000	308,000,000
Collateral Pledged		284,000,000	410,000,000
Advance Facilities | Servicing | Loans payable | $250 advance facility
Debt Instrument [Line Items]
Capacity Amount		250,000,000
Outstanding		177,000,000	171,000,000
Collateral Pledged		200,000,000	209,000,000
Advance Facilities | Servicing | Notes payable to banks
Debt Instrument [Line Items]
Outstanding		548,000,000	669,000,000
Collateral Pledged		702,000,000	853,000,000
Advance Facilities | Servicing | Notes payable to banks | $75 advance facility
Debt Instrument [Line Items]
Capacity Amount		75,000,000
Outstanding		35,000,000	40,000,000
Collateral Pledged		52,000,000	45,000,000
Warehouse Facilities | Originations
Debt Instrument [Line Items]
Outstanding		817,000,000	817,000,000
Warehouse Facilities | Originations | Notes payable to banks
Debt Instrument [Line Items]
Collateral Pledged		910,000,000	910,000,000
Warehouse Facilities | Originations | Notes payable to banks | $1,500 warehouse facility
Debt Instrument [Line Items]
Capacity Amount		1,500,000,000
Outstanding		162,000,000	206,000,000
Collateral Pledged		163,000,000	272,000,000
Warehouse Facilities | Originations | Notes payable to banks | $750 warehouse facility
Debt Instrument [Line Items]
Capacity Amount		750,000,000
Outstanding		115,000,000	135,000,000
Collateral Pledged		150,000,000	133,000,000
Warehouse Facilities | Originations | Notes payable to banks | $750 warehouse facility
Debt Instrument [Line Items]
Capacity Amount		750,000,000
Outstanding		124,000,000	202,000,000
Collateral Pledged		130,000,000	209,000,000
Warehouse Facilities | Originations | Notes payable to banks | $500 warehouse facility
Debt Instrument [Line Items]
Capacity Amount		500,000,000
Outstanding		39,000,000	76,000,000
Collateral Pledged		44,000,000	80,000,000
Warehouse Facilities | Originations | Notes payable to banks | $500 warehouse facility(2)
Debt Instrument [Line Items]
Capacity Amount		500,000,000
Outstanding		88,000,000	31,000,000
Collateral Pledged		90,000,000	32,000,000
Warehouse Facilities | Originations | Notes payable to banks | $500 warehouse facility(2) | Subsequent Event
Debt Instrument [Line Items]
Capacity Amount	$ 350,000,000
Warehouse Facilities | Originations | Notes payable to banks | $300 warehouse facility
Debt Instrument [Line Items]
Capacity Amount		300,000,000
Outstanding		137,000,000	115,000,000
Collateral Pledged		141,000,000	117,000,000
Warehouse Facilities | Originations | Notes payable to banks | $250 warehouse facility(3)
Debt Instrument [Line Items]
Capacity Amount		250,000,000
Outstanding		14,000,000	14,000,000
Collateral Pledged		16,000,000	17,000,000
Warehouse Facilities | Originations | Notes payable to banks | $200 warehouse facility
Debt Instrument [Line Items]
Capacity Amount		200,000,000
Outstanding		48,000,000	18,000,000
Collateral Pledged		50,000,000	21,000,000
Warehouse Facilities | Originations | Notes payable to banks | $200 warehouse facility
Debt Instrument [Line Items]
Capacity Amount		200,000,000
Outstanding		45,000,000	0
Collateral Pledged		70,000,000	0
Warehouse Facilities | Originations | Notes payable to banks | $100 warehouse facility
Debt Instrument [Line Items]
Capacity Amount		100,000,000
Outstanding		40,000,000	19,000,000
Collateral Pledged		51,000,000	28,000,000
Warehouse Facilities | Originations | Notes payable to banks | $100 warehouse facility
Debt Instrument [Line Items]
Capacity Amount		100,000,000
Outstanding		0	0
Collateral Pledged		0	0
Warehouse Facilities | Originations | Notes payable to banks | $75 warehouse facility
Debt Instrument [Line Items]
Capacity Amount		75,000,000
Outstanding		5,000,000	1,000,000
Collateral Pledged		5,000,000	1,000,000
Warehouse Facilities | Originations | Notes payable to banks | $1 warehouse facility
Debt Instrument [Line Items]
Capacity Amount		1,000,000
Outstanding		0	0
Collateral Pledged		0	0
Warehouse Facilities | Originations | Notes payable to banks | $1,000 warehouse facility
Debt Instrument [Line Items]
Capacity Amount		1,000,000,000
MSR Facilities | Servicing | Notes payable to banks
Debt Instrument [Line Items]
Outstanding		2,195,000,000	1,410,000,000
Collateral Pledged		6,620,000,000	5,499,000,000
MSR Facilities | Servicing | Notes payable to banks | $1,500 warehouse facility(1)
Debt Instrument [Line Items]
Capacity Amount		1,500,000,000
Outstanding		250,000,000	260,000,000
Collateral Pledged		2,303,000,000	2,284,000,000
MSR Facilities | Servicing | Notes payable to banks | $1,500 warehouse facility
Debt Instrument [Line Items]
Capacity Amount		1,500,000,000
Outstanding		900,000,000	380,000,000
Collateral Pledged		1,324,000,000	927,000,000
MSR Facilities | Servicing | Notes payable to banks | $750 warehouse facility(3)
Debt Instrument [Line Items]
Capacity Amount		750,000,000
Outstanding		325,000,000	380,000,000
Collateral Pledged		1,391,000,000	1,482,000,000
MSR Facilities | Servicing | Notes payable to banks | $500 warehouse facility
Debt Instrument [Line Items]
Capacity Amount		500,000,000
Outstanding		255,000,000	365,000,000
Collateral Pledged		705,000,000	732,000,000
MSR Facilities | Servicing | Notes payable to banks | $500 warehouse facility
Debt Instrument [Line Items]
Capacity Amount		500,000,000
Outstanding		210,000,000	0
Collateral Pledged		396,000,000	0
MSR Facilities | Servicing | Notes payable to banks | $500 warehouse facility
Debt Instrument [Line Items]
Capacity Amount		500,000,000
Outstanding		225,000,000	0
Collateral Pledged		434,000,000	0
MSR Facilities | Servicing | Notes payable to banks | $50 warehouse facility
Debt Instrument [Line Items]
Capacity Amount		50,000,000
Outstanding		30,000,000	25,000,000
Collateral Pledged		67,000,000	74,000,000
MSR Facilities | Servicing | Notes payable to banks | $1750 warehouse facility
Debt Instrument [Line Items]
Capacity Amount		1,750,000,000
Advance Financing, Internally Allocated | Servicing | Loans payable | $250 advance facility(1)
Debt Instrument [Line Items]
Capacity Amount		250,000,000
MSR Financing, Internally Allocated | Servicing | Notes payable to banks | $1,500 warehouse facility(1)
Debt Instrument [Line Items]
Capacity Amount		1,500,000,000
MSR Financing, Internally Allocated | Servicing | Notes payable to banks | $500 warehouse facility
Debt Instrument [Line Items]
Capacity Amount		750,000,000
Advance, Warehouse and MSR Facilities
Debt Instrument [Line Items]
Outstanding		3,560,000,000	2,896,000,000
Collateral Pledged		8,232,000,000	7,262,000,000
Unamortized debt issuance costs		(15,000,000)	(11,000,000)
Advance, warehouse and MSR facilities, net		$ 3,545,000,000	$ 2,885,000,000