Indebtedness - Advance and Warehouse Facilities Summary (Details) - USD ($) | Apr. 01, 2024 | Mar. 31, 2024 | Dec. 31, 2023 |
Debt Instrument [Line Items] | | | |
Advance, warehouse and MSR facilities, net | | $ 4,087,000,000 | $ 4,302,000,000 |
Advance Facilities | Servicing | Loans payable | $350 advance facility | | | |
Debt Instrument [Line Items] | | | |
Capacity Amount | | 350,000,000 | |
Outstanding | | 122,000,000 | 132,000,000 |
Collateral Pledged | | 158,000,000 | 169,000,000 |
Advance Facilities | Servicing | Loans payable | $250 advance facility(1) | | | |
Debt Instrument [Line Items] | | | |
Capacity Amount | | 250,000,000 | |
Outstanding | | 230,000,000 | 273,000,000 |
Collateral Pledged | | 313,000,000 | 364,000,000 |
Advance Facilities | Servicing | Loans payable | $300 advance facility | | | |
Debt Instrument [Line Items] | | | |
Capacity Amount | | 300,000,000 | |
Outstanding | | 271,000,000 | 250,000,000 |
Collateral Pledged | | 305,000,000 | 326,000,000 |
Advance Facilities | Servicing | Notes payable to banks | | | |
Debt Instrument [Line Items] | | | |
Outstanding | | 650,000,000 | 682,000,000 |
Collateral Pledged | | 825,000,000 | 908,000,000 |
Advance Facilities | Servicing | Notes payable to banks | $50 advance facility(2) | | | |
Debt Instrument [Line Items] | | | |
Capacity Amount | | 50,000,000 | |
Outstanding | | 27,000,000 | 27,000,000 |
Collateral Pledged | | 49,000,000 | 49,000,000 |
Warehouse Facilities | Originations | | | |
Debt Instrument [Line Items] | | | |
Outstanding | | 958,000,000 | 822,000,000 |
Warehouse Facilities | Originations | Notes payable to banks | | | |
Debt Instrument [Line Items] | | | |
Collateral Pledged | | 1,065,000,000 | 915,000,000 |
Warehouse Facilities | Originations | Notes payable to banks | $1,500 warehouse facility | | | |
Debt Instrument [Line Items] | | | |
Capacity Amount | | 1,500,000,000 | |
Outstanding | | 141,000,000 | 107,000,000 |
Collateral Pledged | | 141,000,000 | 104,000,000 |
Warehouse Facilities | Originations | Notes payable to banks | $750 warehouse facility | | | |
Debt Instrument [Line Items] | | | |
Capacity Amount | | 750,000,000 | |
Outstanding | | 138,000,000 | 137,000,000 |
Collateral Pledged | | 175,000,000 | 176,000,000 |
Warehouse Facilities | Originations | Notes payable to banks | $750 warehouse facility | | | |
Debt Instrument [Line Items] | | | |
Capacity Amount | | 750,000,000 | |
Outstanding | | 172,000,000 | 155,000,000 |
Collateral Pledged | | 190,000,000 | 166,000,000 |
Warehouse Facilities | Originations | Notes payable to banks | $500 warehouse facility | | | |
Debt Instrument [Line Items] | | | |
Capacity Amount | | 500,000,000 | |
Outstanding | | 54,000,000 | 72,000,000 |
Collateral Pledged | | 58,000,000 | 78,000,000 |
Warehouse Facilities | Originations | Notes payable to banks | $350 warehouse facility | | | |
Debt Instrument [Line Items] | | | |
Capacity Amount | | 350,000,000 | |
Outstanding | | 138,000,000 | 73,000,000 |
Collateral Pledged | | 141,000,000 | 75,000,000 |
Warehouse Facilities | Originations | Notes payable to banks | $250 warehouse facility(3) | | | |
Debt Instrument [Line Items] | | | |
Capacity Amount | | 250,000,000 | |
Outstanding | | 177,000,000 | 158,000,000 |
Collateral Pledged | | 203,000,000 | 177,000,000 |
Warehouse Facilities | Originations | Notes payable to banks | $200 warehouse facility | | | |
Debt Instrument [Line Items] | | | |
Capacity Amount | | 200,000,000 | |
Outstanding | | 10,000,000 | 82,000,000 |
Collateral Pledged | | 10,000,000 | 84,000,000 |
Warehouse Facilities | Originations | Notes payable to banks | $200 warehouse facility | | | |
Debt Instrument [Line Items] | | | |
Capacity Amount | | 200,000,000 | |
Outstanding | | 11,000,000 | 12,000,000 |
Collateral Pledged | | 21,000,000 | 21,000,000 |
Warehouse Facilities | Originations | Notes payable to banks | $100 warehouse facility | | | |
Debt Instrument [Line Items] | | | |
Capacity Amount | | 100,000,000 | |
Outstanding | | 52,000,000 | 25,000,000 |
Collateral Pledged | | 61,000,000 | 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 (2) | | | |
Debt Instrument [Line Items] | | | |
Capacity Amount | | 100,000,000 | |
Outstanding | | 65,000,000 | 1,000,000 |
Collateral Pledged | | 65,000,000 | 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 | | 1,200,000,000 | |
Warehouse Facilities | Originations | Notes payable to banks | $1500 million MSR facility due April 2026Member | Subsequent Event | | | |
Debt Instrument [Line Items] | | | |
Capacity Amount | $ 1,750,000,000 | | |
Warehouse Facilities | Originations | Notes payable to banks | $1000 Warehouse Facility | | | |
Debt Instrument [Line Items] | | | |
Capacity Amount | | 1,000,000,000 | |
MSR Facilities | Servicing | Notes payable to banks | | | |
Debt Instrument [Line Items] | | | |
Outstanding | | 2,495,000,000 | 2,814,000,000 |
Collateral Pledged | | 8,871,000,000 | 6,958,000,000 |
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 | 300,000,000 |
Collateral Pledged | | 2,334,000,000 | 2,164,000,000 |
MSR Facilities | Servicing | Notes payable to banks | $950 warehouse facility(3) | | | |
Debt Instrument [Line Items] | | | |
Capacity Amount | | 950,000,000 | |
Outstanding | | 585,000,000 | 545,000,000 |
Collateral Pledged | | 1,633,000,000 | 1,306,000,000 |
MSR Facilities | Servicing | Notes payable to banks | $500 warehouse facility | | | |
Debt Instrument [Line Items] | | | |
Capacity Amount | | 500,000,000 | |
Outstanding | | 335,000,000 | 405,000,000 |
Collateral Pledged | | 724,000,000 | 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 | | 788,000,000 | 634,000,000 |
MSR Facilities | Servicing | Notes payable to banks | $500 warehouse facility | | | |
Debt Instrument [Line Items] | | | |
Capacity Amount | | 500,000,000 | |
Outstanding | | 250,000,000 | 250,000,000 |
Collateral Pledged | | 753,000,000 | 677,000,000 |
MSR Facilities | Servicing | Notes payable to banks | $50 warehouse facility | | | |
Debt Instrument [Line Items] | | | |
Capacity Amount | | 50,000,000 | |
Outstanding | | 25,000,000 | 29,000,000 |
Collateral Pledged | | 68,000,000 | 67,000,000 |
MSR Facilities | Servicing | Notes payable to banks | $1750 warehouse facility | | | |
Debt Instrument [Line Items] | | | |
Capacity Amount | | 1,750,000,000 | |
MSR Facilities | Servicing | Notes payable to banks | $1500 million MSR facility due April 2026Member | | | |
Debt Instrument [Line Items] | | | |
Capacity Amount | | 1,500,000,000 | |
Outstanding | | 800,000,000 | 980,000,000 |
Collateral Pledged | | 2,571,000,000 | 1,455,000,000 |
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 | $950 warehouse facility(3) | | | |
Debt Instrument [Line Items] | | | |
Capacity Amount | | 950,000,000 | |
Advance, Warehouse and MSR Facilities | | | |
Debt Instrument [Line Items] | | | |
Outstanding | | 4,103,000,000 | 4,318,000,000 |
Collateral Pledged | | 10,761,000,000 | 8,781,000,000 |
Unamortized debt issuance costs | | (16,000,000) | (16,000,000) |
Advance, warehouse and MSR facilities, net | | $ 4,087,000,000 | $ 4,302,000,000 |