Indebtedness - Notes Payable Summary (Details) - USD ($)	9 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Debt Outstanding	$ 513,000,000	$ 595,000,000
Servicing Segment | Notes Payable, Other
Debt Instrument [Line Items]
Debt outstanding, gross	513,000,000	595,000,000
Debt Outstanding	513,000,000	595,000,000
Collateral Pledged	676,000,000	777,000,000
Servicing Segment | Notes Payable, Other | $325 advance facility
Debt Instrument [Line Items]
Capacity Amount	325,000,000
Debt outstanding, gross	233,000,000	209,000,000
Collateral Pledged	$ 294,000,000	284,000,000
Servicing Segment | Notes Payable, Other | $325 advance facility | LIBOR | Minimum
Debt Instrument [Line Items]
Basis spread on rate	1.50%
Servicing Segment | Notes Payable, Other | $325 advance facility | LIBOR | Maximum
Debt Instrument [Line Items]
Basis spread on rate	6.50%
Servicing Segment | Notes Payable, Other | $250 advance facility
Debt Instrument [Line Items]
Capacity Amount	$ 250,000,000
Debt outstanding, gross	142,000,000	218,000,000
Collateral Pledged	$ 173,000,000	255,000,000
Servicing Segment | Notes Payable, Other | $250 advance facility | LIBOR | Minimum
Debt Instrument [Line Items]
Basis spread on rate	1.50%
Servicing Segment | Notes Payable, Other | $250 advance facility | LIBOR | Maximum
Debt Instrument [Line Items]
Basis spread on rate	2.60%
Servicing Segment | Notes Payable, Other | $200 advance facility
Debt Instrument [Line Items]
Capacity Amount	$ 200,000,000
Debt outstanding, gross	64,000,000	90,000,000
Collateral Pledged	$ 125,000,000	149,000,000
Servicing Segment | Notes Payable, Other | $200 advance facility | LIBOR
Debt Instrument [Line Items]
Basis spread on rate	2.50%
Servicing Segment | Notes Payable, Other | $125 advance facility
Debt Instrument [Line Items]
Capacity Amount	$ 125,000,000
Debt outstanding, gross	74,000,000	78,000,000
Collateral Pledged	$ 84,000,000	89,000,000
Servicing Segment | Notes Payable, Other | $125 advance facility | LIBOR | Minimum
Debt Instrument [Line Items]
Basis spread on rate	1.50%
Servicing Segment | Notes Payable, Other | $125 advance facility | LIBOR | Maximum
Debt Instrument [Line Items]
Basis spread on rate	7.40%
Servicing Segment | Advance facilities
Debt Instrument [Line Items]
Unamortized debt issuance costs	$ 0	0
Originations Segment | Mortgage loans, net
Debt Instrument [Line Items]
Debt Outstanding	3,980,000,000	1,528,000,000
Collateral Pledged	4,119,000,000	1,628,000,000
Originations Segment | Reverse mortgage interests
Debt Instrument [Line Items]
Debt Outstanding	663,000,000	722,000,000
Collateral Pledged	773,000,000	838,000,000
Originations Segment | MSR
Debt Instrument [Line Items]
Debt Outstanding	160,000,000	100,000,000
Collateral Pledged	1,237,000,000	1,686,000,000
Originations Segment | Notes Payable to Banks
Debt Instrument [Line Items]
Debt outstanding, gross	4,643,000,000	2,250,000,000
Collateral Pledged	4,892,000,000	2,466,000,000
Originations Segment | Notes Payable to Banks | $1,500 warehouse facility
Debt Instrument [Line Items]
Capacity Amount	1,500,000,000
Debt outstanding, gross	970,000,000	0
Collateral Pledged	$ 938,000,000	0
Originations Segment | Notes Payable to Banks | $1,500 warehouse facility | LIBOR
Debt Instrument [Line Items]
Basis spread on rate	1.00%
Originations Segment | Notes Payable to Banks | $1,200 warehouse facility
Debt Instrument [Line Items]
Capacity Amount	$ 1,200,000,000
Debt outstanding, gross	734,000,000	560,000,000
Collateral Pledged	$ 779,000,000	622,000,000
Originations Segment | Notes Payable to Banks | $1,200 warehouse facility | LIBOR | Minimum
Debt Instrument [Line Items]
Basis spread on rate	1.70%
Originations Segment | Notes Payable to Banks | $1,200 warehouse facility | LIBOR | Maximum
Debt Instrument [Line Items]
Basis spread on rate	3.50%
Originations Segment | Notes Payable to Banks | $1,000 warehouse facility
Debt Instrument [Line Items]
Capacity Amount	$ 1,000,000,000
Debt outstanding, gross	521,000,000	137,000,000
Collateral Pledged	$ 536,000,000	140,000,000
Originations Segment | Notes Payable to Banks | $1,000 warehouse facility | LIBOR | Minimum
Debt Instrument [Line Items]
Basis spread on rate	1.40%
Originations Segment | Notes Payable to Banks | $1,000 warehouse facility | LIBOR | Maximum
Debt Instrument [Line Items]
Basis spread on rate	2.30%
Originations Segment | Notes Payable to Banks | $800 warehouse facility
Debt Instrument [Line Items]
Capacity Amount	$ 800,000,000
Debt outstanding, gross	586,000,000	464,000,000
Collateral Pledged	$ 643,000,000	514,000,000
Originations Segment | Notes Payable to Banks | $800 warehouse facility | LIBOR | Minimum
Debt Instrument [Line Items]
Basis spread on rate	1.50%
Originations Segment | Notes Payable to Banks | $800 warehouse facility | LIBOR | Maximum
Debt Instrument [Line Items]
Basis spread on rate	2.90%
Originations Segment | Notes Payable to Banks | $750 warehouse facility
Debt Instrument [Line Items]
Capacity Amount	$ 750,000,000
Debt outstanding, gross	511,000,000	119,000,000
Collateral Pledged	$ 524,000,000	122,000,000
Originations Segment | Notes Payable to Banks | $750 warehouse facility | LIBOR | Minimum
Debt Instrument [Line Items]
Basis spread on rate	1.40%
Originations Segment | Notes Payable to Banks | $750 warehouse facility | LIBOR | Maximum
Debt Instrument [Line Items]
Basis spread on rate	2.80%
Originations Segment | Notes Payable to Banks | $600 warehouse facility
Debt Instrument [Line Items]
Capacity Amount	$ 600,000,000
Debt outstanding, gross	214,000,000	151,000,000
Collateral Pledged	$ 251,000,000	168,000,000
Originations Segment | Notes Payable to Banks | $600 warehouse facility | LIBOR | Minimum
Debt Instrument [Line Items]
Basis spread on rate	2.30%
Originations Segment | Notes Payable to Banks | $500 warehouse facility
Debt Instrument [Line Items]
Capacity Amount	$ 500,000,000
Debt outstanding, gross	405,000,000	220,000,000
Collateral Pledged	$ 474,000,000	248,000,000
Originations Segment | Notes Payable to Banks | $500 warehouse facility | LIBOR | Minimum
Debt Instrument [Line Items]
Basis spread on rate	1.50%
Originations Segment | Notes Payable to Banks | $500 warehouse facility | LIBOR | Maximum
Debt Instrument [Line Items]
Basis spread on rate	3.00%
Originations Segment | Notes Payable to Banks | $500 warehouse facility
Debt Instrument [Line Items]
Capacity Amount	$ 500,000,000
Debt outstanding, gross	391,000,000	187,000,000
Collateral Pledged	$ 400,000,000	200,000,000
Originations Segment | Notes Payable to Banks | $500 warehouse facility | LIBOR | Minimum
Debt Instrument [Line Items]
Basis spread on rate	1.50%
Originations Segment | Notes Payable to Banks | $500 warehouse facility | LIBOR | Maximum
Debt Instrument [Line Items]
Basis spread on rate	2.80%
Originations Segment | Notes Payable to Banks | $200 warehouse facility
Debt Instrument [Line Items]
Capacity Amount	$ 200,000,000
Debt outstanding, gross	91,000,000	0
Collateral Pledged	$ 92,000,000	0
Originations Segment | Notes Payable to Banks | $200 warehouse facility | LIBOR
Debt Instrument [Line Items]
Basis spread on rate	1.50%
Originations Segment | Notes Payable to Banks | $200 warehouse facility
Debt Instrument [Line Items]
Capacity Amount	$ 200,000,000
Debt outstanding, gross	91,000,000	18,000,000
Collateral Pledged	$ 94,000,000	19,000,000
Originations Segment | Notes Payable to Banks | $200 warehouse facility | LIBOR
Debt Instrument [Line Items]
Basis spread on rate	1.20%
Originations Segment | Notes Payable to Banks | $200 warehouse facility
Debt Instrument [Line Items]
Capacity Amount	$ 200,000,000
Debt outstanding, gross	67,000,000	103,000,000
Collateral Pledged	$ 94,000,000	132,000,000
Originations Segment | Notes Payable to Banks | $200 warehouse facility | LIBOR
Debt Instrument [Line Items]
Basis spread on rate	2.00%
Originations Segment | Notes Payable to Banks | $200 warehouse facility
Debt Instrument [Line Items]
Capacity Amount	$ 200,000,000
Debt outstanding, gross	21,000,000	0
Collateral Pledged	$ 21,000,000	0
Originations Segment | Notes Payable to Banks | $200 warehouse facility | LIBOR
Debt Instrument [Line Items]
Basis spread on rate	1.50%
Originations Segment | Notes Payable to Banks | $50 warehouse facility
Debt Instrument [Line Items]
Capacity Amount	$ 50,000,000
Debt outstanding, gross	13,000,000	0
Collateral Pledged	$ 16,000,000	0
Originations Segment | Notes Payable to Banks | $50 warehouse facility | LIBOR | Minimum
Debt Instrument [Line Items]
Basis spread on rate	2.00%
Originations Segment | Notes Payable to Banks | $50 warehouse facility | LIBOR | Maximum
Debt Instrument [Line Items]
Basis spread on rate	6.00%
Originations Segment | Notes Payable to Banks | $40 warehouse facility
Debt Instrument [Line Items]
Capacity Amount	$ 40,000,000
Debt outstanding, gross	27,000,000	0
Collateral Pledged	$ 28,000,000	0
Originations Segment | Notes Payable to Banks | $40 warehouse facility | LIBOR
Debt Instrument [Line Items]
Basis spread on rate	3.30%
Originations Segment | Notes Payable to Banks | $40 warehouse facility
Debt Instrument [Line Items]
Capacity Amount	$ 40,000,000
Debt outstanding, gross	1,000,000	1,000,000
Collateral Pledged	$ 2,000,000	2,000,000
Originations Segment | Notes Payable to Banks | $40 warehouse facility | LIBOR
Debt Instrument [Line Items]
Basis spread on rate	3.00%
Originations Segment | Notes Payable to Banks | $500 warehouse facility
Debt Instrument [Line Items]
Capacity Amount	$ 0
Debt outstanding, gross	0	290,000,000
Collateral Pledged	$ 0	299,000,000
Originations Segment | Notes Payable to Banks | $500 warehouse facility | LIBOR | Minimum
Debt Instrument [Line Items]
Basis spread on rate	2.00%
Originations Segment | Notes Payable to Banks | $500 warehouse facility | LIBOR | Maximum
Debt Instrument [Line Items]
Basis spread on rate	2.30%
Originations Segment | Mortgage servicing rights
Debt Instrument [Line Items]
Debt outstanding, gross	$ 160,000,000	100,000,000
Collateral Pledged	1,237,000,000	1,686,000,000
Originations Segment | Mortgage servicing rights | $400 warehouse facility
Debt Instrument [Line Items]
Capacity Amount	400,000,000
Debt outstanding, gross	150,000,000	100,000,000
Collateral Pledged	$ 839,000,000	928,000,000
Originations Segment | Mortgage servicing rights | $400 warehouse facility | LIBOR | Minimum
Debt Instrument [Line Items]
Basis spread on rate	3.50%
Originations Segment | Mortgage servicing rights | $400 warehouse facility | LIBOR | Maximum
Debt Instrument [Line Items]
Basis spread on rate	6.10%
Originations Segment | Mortgage servicing rights | $400 warehouse facility
Debt Instrument [Line Items]
Capacity Amount	$ 400,000,000
Debt outstanding, gross	0	0
Collateral Pledged	$ 193,000,000	226,000,000
Originations Segment | Mortgage servicing rights | $400 warehouse facility | LIBOR
Debt Instrument [Line Items]
Basis spread on rate	2.30%
Originations Segment | Mortgage servicing rights | $150 warehouse facility
Debt Instrument [Line Items]
Capacity Amount	$ 150,000,000
Debt outstanding, gross	0	0
Collateral Pledged	$ 121,000,000	430,000,000
Originations Segment | Mortgage servicing rights | $150 warehouse facility | LIBOR
Debt Instrument [Line Items]
Basis spread on rate	2.80%
Originations Segment | Mortgage servicing rights | $50 warehouse facility
Debt Instrument [Line Items]
Capacity Amount	$ 50,000,000
Debt outstanding, gross	10,000,000	0
Collateral Pledged	$ 84,000,000	102,000,000
Originations Segment | Mortgage servicing rights | $50 warehouse facility | LIBOR
Debt Instrument [Line Items]
Basis spread on rate	2.80%
Originations Segment | Warehouse Facilities
Debt Instrument [Line Items]
Debt outstanding, gross	$ 4,803,000,000	2,350,000,000
Unamortized debt issuance costs	(1,000,000)	(1,000,000)
Debt Outstanding	4,802,000,000	2,349,000,000
Collateral Pledged	$ 6,129,000,000	$ 4,152,000,000