Indebtedness - Advance and Warehouse Facilities Summary (Details) - USD ($)	Mar. 31, 2022	Dec. 31, 2021
Debt Instrument [Line Items]
Advance and warehouse facilities, net	$ 4,795,000,000	$ 4,997,000,000
Advance Facilities | Servicing | Loans payable | $350 advance facility
Debt Instrument [Line Items]
Capacity Amount	350,000,000
Debt outstanding, gross	156,000,000	160,000,000
Collateral Pledged	189,000,000	197,000,000
Advance Facilities | Servicing | Loans payable | $350 advance facility
Debt Instrument [Line Items]
Capacity Amount	350,000,000
Debt outstanding, gross	158,000,000	162,000,000
Collateral Pledged	186,000,000	190,000,000
Advance Facilities | Servicing | Notes payable to banks
Debt Instrument [Line Items]
Debt outstanding, gross	586,000,000	614,000,000
Collateral Pledged	766,000,000	794,000,000
Advance Facilities | Servicing | Notes payable to banks | $75 advance facility
Debt Instrument [Line Items]
Capacity Amount	75,000,000
Debt outstanding, gross	53,000,000	58,000,000
Collateral Pledged	79,000,000	89,000,000
Warehouse Facilities | Originations | Notes payable to banks
Debt Instrument [Line Items]
Debt outstanding, gross	3,419,000,000	4,125,000,000
Collateral Pledged	3,667,000,000	4,327,000,000
Warehouse Facilities | Originations | Notes payable to banks | $4,000 warehouse facility
Debt Instrument [Line Items]
Capacity Amount	4,000,000,000
Debt outstanding, gross	987,000,000	1,224,000,000
Collateral Pledged	1,118,000,000	1,341,000,000
Warehouse Facilities | Originations | Notes payable to banks | $2,500 warehouse facility
Debt Instrument [Line Items]
Capacity Amount	2,500,000,000
Debt outstanding, gross	746,000,000	991,000,000
Collateral Pledged	772,000,000	1,024,000,000
Warehouse Facilities | Originations | Notes payable to banks | $1,600 warehouse facility
Debt Instrument [Line Items]
Capacity Amount	1,600,000,000
Debt outstanding, gross	148,000,000	409,000,000
Collateral Pledged	161,000,000	425,000,000
Warehouse Facilities | Originations | Notes payable to banks | $1,500 warehouse facility
Debt Instrument [Line Items]
Capacity Amount	1,500,000,000
Debt outstanding, gross	349,000,000	356,000,000
Collateral Pledged	352,000,000	345,000,000
Warehouse Facilities | Originations | Notes payable to banks | $750 warehouse facility
Debt Instrument [Line Items]
Capacity Amount	750,000,000
Debt outstanding, gross	256,000,000	256,000,000
Collateral Pledged	272,000,000	270,000,000
Warehouse Facilities | Originations | Notes payable to banks | $550 warehouse facility
Debt Instrument [Line Items]
Capacity Amount	550,000,000
Debt outstanding, gross	48,000,000	87,000,000
Collateral Pledged	49,000,000	89,000,000
Warehouse Facilities | Originations | Notes payable to banks | $500 Warehouse Facility
Debt Instrument [Line Items]
Capacity Amount	500,000,000
Debt outstanding, gross	216,000,000	188,000,000
Collateral Pledged	224,000,000	194,000,000
Warehouse Facilities | Originations | Notes payable to banks | $500 warehouse facility
Debt Instrument [Line Items]
Capacity Amount	500,000,000
Debt outstanding, gross	284,000,000	419,000,000
Collateral Pledged	293,000,000	430,000,000
Warehouse Facilities | Originations | Notes payable to banks | $500 warehouse facility
Debt Instrument [Line Items]
Capacity Amount	500,000,000
Debt outstanding, gross	137,000,000	39,000,000
Collateral Pledged	163,000,000	39,000,000
Warehouse Facilities | Originations | Notes payable to banks | $500 Million Warehouse Facility Due August 2023
Debt Instrument [Line Items]
Capacity Amount	500,000,000
Debt outstanding, gross	178,000,000	38,000,000
Collateral Pledged	184,000,000	39,000,000
Warehouse Facilities | Originations | Notes payable to banks | $325 warehouse facility
Debt Instrument [Line Items]
Capacity Amount	325,000,000
Debt outstanding, gross	38,000,000	67,000,000
Collateral Pledged	38,000,000	67,000,000
Warehouse Facilities | Originations | Notes payable to banks | $250 warehouse facility(3)
Debt Instrument [Line Items]
Capacity Amount	250,000,000	600
Debt outstanding, gross	1,000,000	5,000,000
Collateral Pledged	2,000,000	6,000,000
Warehouse Facilities | Originations | Notes payable to banks | $200 warehouse facility
Debt Instrument [Line Items]
Capacity Amount	200,000,000
Debt outstanding, gross	31,000,000	46,000,000
Collateral Pledged	39,000,000	58,000,000
Warehouse Facilities | Originations | Notes payable to banks | $30 warehouse facility
Debt Instrument [Line Items]
Capacity Amount	30,000,000
Debt outstanding, gross	0	0
Collateral Pledged	0	0
Warehouse Facilities | Originations | Notes payable to banks | $2,000 warehouse facility
Debt Instrument [Line Items]
Capacity Amount	2,000,000,000
MSR Facilities | Servicing | Notes payable to banks
Debt Instrument [Line Items]
Debt outstanding, gross	800,000,000	270,000,000
Collateral Pledged	3,789,000,000	2,814,000,000
MSR Facilities | Servicing | Notes payable to banks | $800 warehouse facility
Debt Instrument [Line Items]
Capacity Amount	800,000,000
Debt outstanding, gross	260,000,000	260,000,000
Collateral Pledged	1,345,000,000	1,107,000,000
MSR Facilities | Servicing | Notes payable to banks | $400 warehouse facility
Debt Instrument [Line Items]
Capacity Amount	400,000,000
Debt outstanding, gross	300,000,000	0
Collateral Pledged	1,246,000,000	838,000,000
MSR Facilities | Servicing | Notes payable to banks | $400 warehouse facility
Debt Instrument [Line Items]
Capacity Amount	400,000,000
Debt outstanding, gross	215,000,000	0
Collateral Pledged	1,114,000,000	745,000,000
MSR Facilities | Servicing | Notes payable to banks | $50 warehouse facility
Debt Instrument [Line Items]
Capacity Amount	50,000,000
Debt outstanding, gross	25,000,000	10,000,000
Collateral Pledged	84,000,000	124,000,000
MSR Facilities | Servicing | Notes payable to banks | $1,200 warehouse facility
Debt Instrument [Line Items]
Capacity Amount	1,200,000,000	1,200,000,000
Advance Financing, Internally Allocated | Servicing | Loans payable | $400 advance facility
Debt Instrument [Line Items]
Capacity Amount	400,000,000	940,000,000
Debt outstanding, gross	219,000,000	234,000,000
Collateral Pledged	312,000,000	318,000,000
MSR Financing, Internally Allocated | Servicing | Notes payable to banks | $800 warehouse facility
Debt Instrument [Line Items]
Capacity Amount	800,000,000	260,000,000
MSR Financing, Internally Allocated | Servicing | Notes payable to banks | $400 warehouse facility
Debt Instrument [Line Items]
Capacity Amount	400,000,000
Advance, Warehouse and MSR Facilities
Debt Instrument [Line Items]
Debt outstanding, gross	4,805,000,000	5,009,000,000
Collateral Pledged	8,222,000,000	7,935,000,000
Unamortized debt issuance costs	(10,000,000)	(12,000,000)
Advance and warehouse facilities, net	$ 4,795,000,000	$ 4,997,000,000