Securitizations and Financings - Assets and Liabilities of Consolidated VIEs (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) special_purpose_entity	Dec. 31, 2018 USD ($)	Jul. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Number Of VIEs | special_purpose_entity	4
Transfers accounted for as secured borrowings, assets	$ 606	$ 816
Reverse secured borrowings, assets	5,272	6,791
Transfers accounted for as secured borrowings, liabilities	360	535
Reverse secured borrowings, liabilities	5,277	6,699
UPB, purchase discount	46	42	$ 82	$ 89
Residential Mortgage | Restricted cash
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers accounted for as secured borrowings, assets	66	70
Reverse secured borrowings, assets	42	63
Residential Mortgage | Reverse mortgage interests
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	5,230	6,728
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	540	628
Reverse secured borrowings, assets	0	0
Residential Mortgage | Mortgage loans held for investment
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers accounted for as secured borrowings, assets	0	118
Reverse secured borrowings, assets	0	0
Residential Mortgage | Other assets
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	0	0
Residential Mortgage | Advance facilities
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers accounted for as secured borrowings, liabilities	359	505
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	1	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	4,284	5,607
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	333	0
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	302	0
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	209	326
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	148	250
Residential Mortgage | Trust 2018-1 | 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	0	284
Residential Mortgage | Trust 2017-2 | 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	231
Residential Mortgage | Other nonrecourse debt
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers accounted for as secured borrowings, liabilities	0	29
Reverse secured borrowings, liabilities	$ 0	$ 0