Securitizations and Financings - Assets and Liabilities of Consolidated VIEs (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Purchase discount	$ 53	$ 61
Residential mortgage
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Assets - transfers accounted for as secured borrowings	495	488
Assets - reverse secured borrowings	4,186	4,379
Liabilities - transfers accounted for as secured borrowings	337	359
Liabilities - reverse secured borrowings	4,212	4,416
Residential mortgage \| Restricted cash
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Assets - transfers accounted for as secured borrowings	80	47
Assets - reverse secured borrowings	27	23
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	415	441
Assets - reverse secured borrowings	0	0
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	4,159	4,356
Residential mortgage \| Advance facilities
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Liabilities - transfers accounted for as secured borrowings	337	358
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	0
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	3,306	3,473
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	471	490
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	232	241
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	$ 203	$ 212

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