Securitizations and Financings - Assets and Liabilities of Consolidated VIEs (Details) $ in Millions	6 Months Ended
Jun. 30, 2020 USD ($) special_purpose_entity	Dec. 31, 2019 USD ($)
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Number of SPEs \| special_purpose_entity	4
Assets - transfers accounted for as secured borrowings	$ 587	$ 606
Assets - reverse secured borrowings	4,666	5,272
Liabilities - transfers accounted for as secured borrowings	400	360
Liabilities - reverse secured borrowings	4,700	5,277
Purchase discount	59	46
Residential mortgage \| Restricted cash
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Assets - transfers accounted for as secured borrowings	95	66
Assets - reverse secured borrowings	27	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	4,639	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	492	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	399	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	1	1
Liabilities - reverse secured borrowings	1	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	3,875	4,284
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	274	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	244	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	179	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	$ 127	$ 148

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