Securitizations and Financings - Assets and Liabilities of Consolidated VIEs (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Purchase discount	$ 62	$ 46
Residential mortgage
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Assets - transfers accounted for as secured borrowings	474	606
Assets - reverse secured borrowings	4,628	5,272
Liabilities - transfers accounted for as secured borrowings	347	360
Liabilities - reverse secured borrowings	4,665	5,277
Residential mortgage \| Restricted cash
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Assets - transfers accounted for as secured borrowings	44	66
Assets - reverse secured borrowings	25	42
Residential mortgage \| Reverse mortgage interests
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Assets - transfers accounted for as secured borrowings	0	0
Assets - reverse secured borrowings	4,603	5,230
Residential mortgage \| Advances and other receivables, net
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Assets - transfers accounted for as secured borrowings	430	540
Assets - reverse secured borrowings	0	0
Residential mortgage \| Advance facilities
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Liabilities - transfers accounted for as secured borrowings	347	359
Liabilities - reverse secured borrowings	0	0
Residential mortgage \| Payables and other liabilities
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Liabilities - transfers accounted for as secured borrowings	0	1
Liabilities - reverse secured borrowings	0	1
Residential mortgage \| Participating interest financing
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Liabilities - transfers accounted for as secured borrowings	0	0
Liabilities - reverse secured borrowings	3,664	4,284
Residential mortgage \| Trust 2020-1 \| HECM Securitizations (HMBS)
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Liabilities - transfers accounted for as secured borrowings	0	0
Liabilities - reverse secured borrowings	516	0
Residential mortgage \| Trust 2019-2 \| HECM Securitizations (HMBS)
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Liabilities - transfers accounted for as secured borrowings	0	0
Liabilities - reverse secured borrowings	259	333
Residential mortgage \| Trust 2019-1 \| HECM Securitizations (HMBS)
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Liabilities - transfers accounted for as secured borrowings	0	0
Liabilities - reverse secured borrowings	226	302
Residential mortgage \| Trust 2018-3 \| HECM Securitizations (HMBS)
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Liabilities - transfers accounted for as secured borrowings	0	0
Liabilities - reverse secured borrowings	0	209
Residential mortgage \| Trust 2018-2 \| HECM Securitizations (HMBS)
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Liabilities - transfers accounted for as secured borrowings	0	0
Liabilities - reverse secured borrowings	$ 0	$ 148

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