Indebtedness - Advance and Warehouse Facilities Summary (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Total advance and warehouse facilities, net(15)	$ 4,997,000,000	$ 6,258,000,000
Advance, Warehouse and MSR Facilities
Debt Instrument [Line Items]
Outstanding	5,009,000,000	6,774,000,000
Collateral Pledged	7,935,000,000	8,114,000,000
Unamortized debt issuance costs	(12,000,000)	(11,000,000)
Total advance and warehouse facilities, net(15)	4,997,000,000	6,763,000,000
Loans Payable | Servicing | $940 Advance Facility Due August 2023 | Advance Financing, Internally Allocated
Debt Instrument [Line Items]
Capacity Amount	940,000,000	640,000,000
Outstanding	234,000,000	235,000,000
Collateral Pledged	318,000,000	305,000,000
Loans Payable | Servicing | $940 Advance Facility Due August 2023 | Advance Facilities, Internally Allocated
Debt Instrument [Line Items]
Capacity Amount	940,000,000
Loans Payable | Servicing | $350 Advance Facility Due October 2022 | Advance Facilities
Debt Instrument [Line Items]
Capacity Amount	350,000,000	425,000,000
Outstanding	160,000,000	192,000,000
Collateral Pledged	197,000,000	246,000,000
Loans Payable | Servicing | $350 Advance Facility Due January 2022 | Advance Facilities
Debt Instrument [Line Items]
Capacity Amount	350,000,000	875,000,000
Loans Payable | Servicing | $640 advance facility | Advance Facilities
Debt Instrument [Line Items]
Capacity Amount	350,000,000
Outstanding	162,000,000	168,000,000
Collateral Pledged	190,000,000	195,000,000
Loans Payable | Servicing | $75 Advance facility | Advance Facilities
Debt Instrument [Line Items]
Capacity Amount	$ 75,000,000	100,000,000
Loans Payable | LIBOR | Servicing | $940 Advance Facility Due August 2023 | Advance Facilities
Debt Instrument [Line Items]
Interest Rate	3.50%
Loans Payable | Minimum | LIBOR | Servicing | $350 Advance Facility Due October 2022 | Advance Facilities
Debt Instrument [Line Items]
Interest Rate	1.10%
Loans Payable | Minimum | CPRATE | Servicing | $640 advance facility | Advance Facilities
Debt Instrument [Line Items]
Interest Rate	1.50%
Loans Payable | Maximum | LIBOR | Servicing | $350 Advance Facility Due October 2022 | Advance Facilities
Debt Instrument [Line Items]
Interest Rate	6.50%
Loans Payable | Maximum | CPRATE | Servicing | $640 advance facility | Warehouse Facilities
Debt Instrument [Line Items]
Interest Rate	6.50%
Notes Payable to Banks | Servicing | Advance Facilities
Debt Instrument [Line Items]
Outstanding	$ 614,000,000	669,000,000
Collateral Pledged	794,000,000	844,000,000
Notes Payable to Banks | Servicing | MSR Facilities
Debt Instrument [Line Items]
Outstanding	270,000,000	270,000,000
Collateral Pledged	2,814,000,000	1,217,000,000
Notes Payable to Banks | Servicing | $260 warehouse facility | MSR Facilities
Debt Instrument [Line Items]
Capacity Amount	260,000,000
Outstanding	260,000,000	260,000,000
Collateral Pledged	1,107,000,000	668,000,000
Notes Payable to Banks | Servicing | $260 warehouse facility | MSR Financing, Internally Allocated
Debt Instrument [Line Items]
Capacity Amount	260,000,000	260,000,000
Notes Payable to Banks | Servicing | $150 warehouse facility | MSR Facilities
Debt Instrument [Line Items]
Capacity Amount	50,000,000
Outstanding	10,000,000	10,000,000
Collateral Pledged	124,000,000	74,000,000
Notes Payable to Banks | Servicing | $1200 warehouse facility | MSR Facilities
Debt Instrument [Line Items]
Capacity Amount	1,200,000,000	900,000,000
Notes Payable to Banks | Servicing | $400 Warehouse Facility Due August 2022 | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	400,000,000	200,000,000
Notes Payable to Banks | Servicing | $400 Warehouse Facility Due August 2022 | MSR Facilities
Debt Instrument [Line Items]
Capacity Amount	400,000,000
Outstanding	0	0
Collateral Pledged	838,000,000	247,000,000
Notes Payable to Banks | Servicing | $75 Advance facility | Advance Facilities
Debt Instrument [Line Items]
Capacity Amount	75,000,000
Outstanding	58,000,000	74,000,000
Collateral Pledged	89,000,000	98,000,000
Notes Payable to Banks | Servicing | $400 Warehouse Facility, Due September 2023 | MSR Facilities
Debt Instrument [Line Items]
Capacity Amount		150,000,000
Notes Payable to Banks | Servicing | $400 Warehouse Facility, Due September 2023 | MSR Financing, Internally Allocated
Debt Instrument [Line Items]
Capacity Amount	400,000,000
Outstanding	0	0
Collateral Pledged	745,000,000	228,000,000
Notes Payable to Banks | Originations | Warehouse Facilities
Debt Instrument [Line Items]
Outstanding	4,125,000,000	5,835,000,000
Collateral Pledged	4,327,000,000	6,053,000,000
Notes Payable to Banks | Originations | $750 warehouse facility due October 2021 | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	750,000,000	1,200,000,000
Outstanding	256,000,000	787,000,000
Collateral Pledged	270,000,000	839,000,000
Notes Payable to Banks | Originations | $4000 Warehouse Facility Due February 2023 | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	4,000,000,000	2,000,000,000
Outstanding	1,224,000,000	339,000,000
Collateral Pledged	1,341,000,000	392,000,000
Notes Payable to Banks | Originations | $2500 Warehouse Facility Due October 2022 | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	2,500,000,000	1,500,000,000
Outstanding	991,000,000	1,003,000,000
Collateral Pledged	1,024,000,000	1,037,000,000
Notes Payable to Banks | Originations | $1600 Warehouse Facility Due September 2022 | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	1,600,000,000
Outstanding	409,000,000	1,067,000,000
Collateral Pledged	425,000,000	1,128,000,000
Notes Payable to Banks | Originations | $1500 Warehouse Facility Due June 2022 | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	1,500,000,000
Outstanding	356,000,000	1,081,000,000
Collateral Pledged	345,000,000	1,028,000,000
Notes Payable to Banks | Originations | $600 Warehouse Facility Due February 2022 | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	600,000,000
Outstanding	5,000,000	187,000,000
Collateral Pledged	6,000,000	222,000,000
Notes Payable to Banks | Originations | $550 Million Warehouse Facility Due August 2022 | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	550,000,000	750,000,000
Outstanding	87,000,000	477,000,000
Collateral Pledged	89,000,000	492,000,000
Notes Payable to Banks | Originations | $500 Million Warehouse Facility Due June 2023 | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	500,000,000
Outstanding	188,000,000	0
Collateral Pledged	194,000,000	0
Notes Payable to Banks | Originations | $500 Million Warehouse Facility Due September 2022 | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	500,000,000	750,000,000
Outstanding	419,000,000	562,000,000
Collateral Pledged	430,000,000	574,000,000
Notes Payable to Banks | Originations | $500 Million Warehouse Facility Due June 2022 | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	500,000,000
Outstanding	39,000,000	0
Collateral Pledged	39,000,000	0
Notes Payable to Banks | Originations | $500 Million Warehouse Facility Due August 2023 | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	500,000,000
Outstanding	38,000,000	0
Collateral Pledged	39,000,000	0
Notes Payable to Banks | Originations | $200 Million Warehouse Facility Due October 2021 | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	200,000,000
Outstanding	0	131,000,000
Collateral Pledged	0	134,000,000
Notes Payable to Banks | Originations | $200 Warehouse Facility Due April 2022 | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	200,000,000	50,000,000
Outstanding	46,000,000	37,000,000
Collateral Pledged	58,000,000	42,000,000
Notes Payable to Banks | Originations | $30 Million Warehouse Facility, Due January 2022 | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	30,000,000
Outstanding	0	1,000,000
Collateral Pledged	0	1,000,000
Notes Payable to Banks | Originations | $2000 Warehouse Facility | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	2,000,000,000	1,500,000,000
Notes Payable to Banks | Originations | $505 Warehouse Facility related to Discontinued Ops | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	505,000,000
Notes Payable to Banks | Originations | $300 warehouse facility | Warehouse Facilities
Debt Instrument [Line Items]
Capacity Amount	325,000,000
Outstanding	67,000,000	163,000,000
Collateral Pledged	$ 67,000,000	$ 164,000,000
Notes Payable to Banks | LIBOR | Servicing | $260 warehouse facility | MSR Facilities
Debt Instrument [Line Items]
Interest Rate	3.50%
Notes Payable to Banks | LIBOR | Servicing | $150 warehouse facility | MSR Facilities
Debt Instrument [Line Items]
Interest Rate	2.80%
Notes Payable to Banks | LIBOR | Servicing | $400 Warehouse Facility Due August 2022 | MSR Facilities
Debt Instrument [Line Items]
Interest Rate	3.00%
Notes Payable to Banks | LIBOR | Servicing | $75 Advance facility | Advance Facilities
Debt Instrument [Line Items]
Interest Rate	2.00%
Notes Payable to Banks | LIBOR | Servicing | $400 Warehouse Facility, Due September 2023 | MSR Financing, Internally Allocated
Debt Instrument [Line Items]
Interest Rate	3.00%
Notes Payable to Banks | LIBOR | Originations | $1500 Warehouse Facility Due June 2022 | Warehouse Facilities
Debt Instrument [Line Items]
Interest Rate	1.50%
Notes Payable to Banks | LIBOR | Originations | $600 Warehouse Facility Due February 2022 | Warehouse Facilities
Debt Instrument [Line Items]
Interest Rate	2.50%
Notes Payable to Banks | LIBOR | Originations | $550 Million Warehouse Facility Due August 2022 | Warehouse Facilities
Debt Instrument [Line Items]
Interest Rate	1.50%
Notes Payable to Banks | LIBOR | Originations | $500 Million Warehouse Facility Due August 2023 | Warehouse Facilities
Debt Instrument [Line Items]
Interest Rate	1.70%
Notes Payable to Banks | LIBOR | Originations | $200 Million Warehouse Facility Due October 2021 | Warehouse Facilities
Debt Instrument [Line Items]
Interest Rate	1.80%
Notes Payable to Banks | LIBOR | Originations | $30 Million Warehouse Facility, Due January 2022 | Warehouse Facilities
Debt Instrument [Line Items]
Interest Rate	3.30%
Notes Payable to Banks | LIBOR | Originations | $300 warehouse facility | Warehouse Facilities
Debt Instrument [Line Items]
Interest Rate	1.50%
Notes Payable to Banks | Minimum | LIBOR | Originations | $750 warehouse facility due October 2021 | Warehouse Facilities
Debt Instrument [Line Items]
Interest Rate	1.50%
Notes Payable to Banks | Minimum | LIBOR | Originations | $4000 Warehouse Facility Due February 2023 | Warehouse Facilities
Debt Instrument [Line Items]
Interest Rate	1.60%
Notes Payable to Banks | Minimum | LIBOR | Originations | $2500 Warehouse Facility Due October 2022 | Warehouse Facilities
Debt Instrument [Line Items]
Interest Rate	1.50%
Notes Payable to Banks | Minimum | LIBOR | Originations | $1600 Warehouse Facility Due September 2022 | Warehouse Facilities
Debt Instrument [Line Items]
Interest Rate	1.50%
Notes Payable to Banks | Minimum | LIBOR | Originations | $500 Million Warehouse Facility Due June 2023 | Warehouse Facilities
Debt Instrument [Line Items]
Interest Rate	1.60%
Notes Payable to Banks | Minimum | LIBOR | Originations | $500 Million Warehouse Facility Due September 2022 | Warehouse Facilities
Debt Instrument [Line Items]
Interest Rate	1.50%
Notes Payable to Banks | Minimum | LIBOR | Originations | $500 Million Warehouse Facility Due June 2022 | Warehouse Facilities
Debt Instrument [Line Items]
Interest Rate	1.50%
Notes Payable to Banks | Minimum | LIBOR | Originations | $200 Warehouse Facility Due April 2022 | Warehouse Facilities
Debt Instrument [Line Items]
Interest Rate	1.60%
Notes Payable to Banks | Maximum | LIBOR | Originations | $750 warehouse facility due October 2021 | Warehouse Facilities
Debt Instrument [Line Items]
Interest Rate	3.00%
Notes Payable to Banks | Maximum | LIBOR | Originations | $4000 Warehouse Facility Due February 2023 | Warehouse Facilities
Debt Instrument [Line Items]
Interest Rate	2.20%
Notes Payable to Banks | Maximum | LIBOR | Originations | $2500 Warehouse Facility Due October 2022 | Warehouse Facilities
Debt Instrument [Line Items]
Interest Rate	1.90%
Notes Payable to Banks | Maximum | LIBOR | Originations | $1600 Warehouse Facility Due September 2022 | Warehouse Facilities
Debt Instrument [Line Items]
Interest Rate	3.00%
Notes Payable to Banks | Maximum | LIBOR | Originations | $500 Million Warehouse Facility Due June 2023 | Warehouse Facilities
Debt Instrument [Line Items]
Interest Rate	3.00%
Notes Payable to Banks | Maximum | LIBOR | Originations | $500 Million Warehouse Facility Due September 2022 | Warehouse Facilities
Debt Instrument [Line Items]
Interest Rate	1.80%
Notes Payable to Banks | Maximum | LIBOR | Originations | $500 Million Warehouse Facility Due June 2022 | Warehouse Facilities
Debt Instrument [Line Items]
Interest Rate	4.00%
Notes Payable to Banks | Maximum | LIBOR | Originations | $200 Warehouse Facility Due April 2022 | Warehouse Facilities
Debt Instrument [Line Items]
Interest Rate	4.90%