Securitizations and Financings - Assets and Liabilities of Consolidated VIEs (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
UPB, purchase discount	$ 61	$ 46
Residential Mortgage
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers accounted for as secured borrowings, assets	488	606
Reverse secured borrowings, assets	4,379	5,272
Transfers accounted for as secured borrowings, liabilities	359	360
Reverse secured borrowings, liabilities	4,416	5,277
Residential Mortgage \| Restricted cash
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers accounted for as secured borrowings, assets	47	66
Reverse secured borrowings, assets	23	42
Residential Mortgage \| Advances and other receivables, net
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers accounted for as secured borrowings, assets	441	540
Reverse secured borrowings, assets	0	0
Residential Mortgage \| Reverse mortgage interests, net
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers accounted for as secured borrowings, assets	0	0
Reverse secured borrowings, assets	4,356	5,230
Residential Mortgage \| Advance facilities
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers accounted for as secured borrowings, liabilities	358	359
Reverse secured borrowings, liabilities	0	0
Residential Mortgage \| Payables and other liabilities
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers accounted for as secured borrowings, liabilities	1	1
Reverse secured borrowings, liabilities	0	1
Residential Mortgage \| Participating interest financing
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers accounted for as secured borrowings, liabilities	0	0
Reverse secured borrowings, liabilities	3,473	4,284
Residential Mortgage \| Trust 2020-1 \| HECM Securitizations (HMBS)
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers accounted for as secured borrowings, liabilities	0	0
Reverse secured borrowings, liabilities	490	0
Residential Mortgage \| Trust 2019-2 \| HECM Securitizations (HMBS)
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers accounted for as secured borrowings, liabilities	0	0
Reverse secured borrowings, liabilities	241	333
Residential Mortgage \| Trust 2019-1 \| HECM Securitizations (HMBS)
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers accounted for as secured borrowings, liabilities	0	0
Reverse secured borrowings, liabilities	212	302
Residential Mortgage \| Trust 2018-3 \| HECM Securitizations (HMBS)
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers accounted for as secured borrowings, liabilities	0	0
Reverse secured borrowings, liabilities	0	209
Residential Mortgage \| Trust 2018-2 \| HECM Securitizations (HMBS)
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers accounted for as secured borrowings, liabilities	0	0
Reverse secured borrowings, liabilities	$ 0	$ 148

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