Indebtedness - Advance and Warehouse Facilities Summary (Details) - USD ($)	Oct. 01, 2024	Sep. 30, 2024	Jun. 30, 2024	Dec. 31, 2023
Debt Instrument [Line Items]
Advance, warehouse and MSR facilities, net		$ 4,379,000,000		$ 4,302,000,000
Advance Facilities | Servicing | Loans payable | $350 advance facility
Debt Instrument [Line Items]
Capacity Amount		350,000,000
Outstanding		113,000,000		132,000,000
Collateral Pledged		144,000,000		169,000,000
Advance Facilities | Servicing | Loans payable | $500 advance facility(1)
Debt Instrument [Line Items]
Capacity Amount		300,000,000
Outstanding		0		273,000,000
Collateral Pledged		0		364,000,000
Advance Facilities | Servicing | Loans payable | $500 advance facility(2)
Debt Instrument [Line Items]
Capacity Amount		500,000,000
Outstanding		253,000,000		250,000,000
Collateral Pledged		285,000,000		326,000,000
Advance Facilities | Servicing | Loans payable | $30 advance facility(4)
Debt Instrument [Line Items]
Capacity Amount		30,000,000
Outstanding		27,000,000		27,000,000
Collateral Pledged		40,000,000		49,000,000
Advance Facilities | Servicing | Loans payable | $500 Advance Facility Due July 2026
Debt Instrument [Line Items]
Capacity Amount		500,000,000
Outstanding		211,000,000		0
Collateral Pledged		304,000,000		0
Advance Facilities | Servicing | Notes payable to banks
Debt Instrument [Line Items]
Outstanding		604,000,000		682,000,000
Collateral Pledged		773,000,000		908,000,000
Advance Facilities | Servicing | Notes payable to banks | $30 advance facility(4)
Debt Instrument [Line Items]
Capacity Amount		30,000,000
Warehouse Facilities | Originations | Notes payable to banks
Debt Instrument [Line Items]
Outstanding		1,763,000,000		822,000,000
Collateral Pledged		1,885,000,000		915,000,000
Warehouse Facilities | Originations | Notes payable to banks | $500 advance facility(2)
Debt Instrument [Line Items]
Capacity Amount		500,000,000	$ 300,000,000
Warehouse Facilities | Originations | Notes payable to banks | $1,500 warehouse facility
Debt Instrument [Line Items]
Capacity Amount		1,500,000,000
Outstanding		61,000,000		107,000,000
Collateral Pledged		61,000,000		104,000,000
Warehouse Facilities | Originations | Notes payable to banks | $750 warehouse facility
Debt Instrument [Line Items]
Capacity Amount		750,000,000
Outstanding		82,000,000		137,000,000
Collateral Pledged		105,000,000		176,000,000
Warehouse Facilities | Originations | Notes payable to banks | $750 warehouse facility
Debt Instrument [Line Items]
Capacity Amount		750,000,000
Outstanding		530,000,000		155,000,000
Collateral Pledged		558,000,000		166,000,000
Warehouse Facilities | Originations | Notes payable to banks | $500 warehouse facility
Debt Instrument [Line Items]
Capacity Amount		500,000,000
Outstanding		72,000,000		72,000,000
Collateral Pledged		75,000,000		78,000,000
Warehouse Facilities | Originations | Notes payable to banks | $350 warehouse facility(6)
Debt Instrument [Line Items]
Capacity Amount		350,000,000
Outstanding		276,000,000		73,000,000
Collateral Pledged		282,000,000		75,000,000
Warehouse Facilities | Originations | Notes payable to banks | $350 warehouse facility(6) | Subsequent Event
Debt Instrument [Line Items]
Capacity Amount	$ 600,000,000
Warehouse Facilities | Originations | Notes payable to banks | $1,200 warehouse facility(5)
Debt Instrument [Line Items]
Capacity Amount		1,200,000,000
Outstanding		426,000,000		158,000,000
Collateral Pledged		473,000,000		177,000,000
Warehouse Facilities | Originations | Notes payable to banks | $200 warehouse facility
Debt Instrument [Line Items]
Capacity Amount		200,000,000
Outstanding		180,000,000		82,000,000
Collateral Pledged		186,000,000		84,000,000
Warehouse Facilities | Originations | Notes payable to banks | $200 warehouse facility
Debt Instrument [Line Items]
Capacity Amount		200,000,000
Outstanding		0		12,000,000
Collateral Pledged		0		21,000,000
Warehouse Facilities | Originations | Notes payable to banks | $100 warehouse facility
Debt Instrument [Line Items]
Capacity Amount		100,000,000
Outstanding		80,000,000		25,000,000
Collateral Pledged		89,000,000		33,000,000
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 | $100 warehouse facility (4)
Debt Instrument [Line Items]
Capacity Amount		100,000,000
Outstanding		56,000,000		1,000,000
Collateral Pledged		56,000,000		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 | $1,200 warehouse facility
Debt Instrument [Line Items]
Capacity Amount		1,200,000,000
MSR Facilities | Servicing | Notes payable to banks
Debt Instrument [Line Items]
Outstanding		2,035,000,000		2,814,000,000
Collateral Pledged		9,101,000,000		6,958,000,000
MSR Facilities | Servicing | Notes payable to banks | $1750 warehouse facility
Debt Instrument [Line Items]
Capacity Amount		2,000,000,000
MSR Facilities | Servicing | Notes payable to banks | $950 million MSR facility
Debt Instrument [Line Items]
Capacity Amount		950,000,000
Outstanding		155,000,000		545,000,000
Collateral Pledged		1,287,000,000		1,306,000,000
MSR Facilities | Servicing | Notes payable to banks | $1,750 warehouse facility
Debt Instrument [Line Items]
Capacity Amount		1,750,000,000
Outstanding		550,000,000		980,000,000
Collateral Pledged		2,463,000,000		1,455,000,000
MSR Facilities | Servicing | Notes payable to banks | $1,500 warehouse facility(1)
Debt Instrument [Line Items]
Capacity Amount		1,450,000,000
Outstanding		0		300,000,000
Collateral Pledged		0		2,164,000,000
MSR Facilities | Servicing | Notes payable to banks | $500 warehouse facility
Debt Instrument [Line Items]
Capacity Amount		500,000,000
Outstanding		100,000,000		405,000,000
Collateral Pledged		722,000,000		655,000,000
MSR Facilities | Servicing | Notes payable to banks | $500 warehouse facility
Debt Instrument [Line Items]
Capacity Amount		500,000,000
Outstanding		250,000,000		305,000,000
Collateral Pledged		740,000,000		634,000,000
MSR Facilities | Servicing | Notes payable to banks | $500 warehouse facility
Debt Instrument [Line Items]
Capacity Amount		500,000,000
Outstanding		150,000,000		250,000,000
Collateral Pledged		745,000,000		677,000,000
MSR Facilities | Servicing | Notes payable to banks | $50 warehouse facility
Debt Instrument [Line Items]
Capacity Amount		50,000,000
Outstanding		10,000,000		29,000,000
Collateral Pledged		78,000,000		67,000,000
MSR Facilities | Servicing | Notes payable to banks | $500 warehouse facility
Debt Instrument [Line Items]
Capacity Amount		500,000,000
Outstanding		250,000,000		0
Collateral Pledged		501,000,000		0
MSR Facilities | Servicing | Notes payable to banks | $1500 million MSR facility due July 2026
Debt Instrument [Line Items]
Capacity Amount		1,500,000,000
Outstanding		470,000,000		0
Collateral Pledged		2,212,000,000		0
MSR Facilities | Servicing | Notes payable to banks | $500 MSR WH Mizuho Facility Due July 2026
Debt Instrument [Line Items]
Capacity Amount		500,000,000
Outstanding		100,000,000		0
Collateral Pledged		353,000,000		0
Advance Financing, Internally Allocated | Servicing | Loans payable | $500 advance facility(2)
Debt Instrument [Line Items]
Capacity Amount		500,000,000
MSR Financing, Internally Allocated | Servicing | Notes payable to banks | $950 million MSR facility
Debt Instrument [Line Items]
Capacity Amount		950,000,000
MSR Financing, Internally Allocated | Servicing | Notes payable to banks | $1500 million MSR facility due July 2026
Debt Instrument [Line Items]
Capacity Amount		1,500,000,000
Advance, Warehouse and MSR Facilities
Debt Instrument [Line Items]
Outstanding		4,402,000,000		4,318,000,000
Collateral Pledged		11,759,000,000		8,781,000,000
Unamortized debt issuance costs		(23,000,000)		(16,000,000)
Advance, warehouse and MSR facilities, net		$ 4,379,000,000		$ 4,302,000,000