Securitizations and Financings - Assets and Liabilities of Consolidated VIEs (Details) $ in Millions	9 Months Ended
	Sep. 30, 2019 USD ($) special_purpose_entity	Dec. 31, 2018 USD ($)
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Number of SPEs | special_purpose_entity	4
Assets	$ 622	$ 816
Reverse Secured Borrowings, Assets, Carrying Amount	5,517	6,791
Liabilities	450	535
Reverse Secured Borrowings, Liabilities, Carrying Amount	5,522	6,699
Purchase discount	49	42
Residential Mortgage | Restricted cash
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Assets	70	70
Reverse Secured Borrowings, Assets, Carrying Amount	46	63
Residential Mortgage | Reverse mortgage interests
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Assets	0	0
Reverse Secured Borrowings, Assets, Carrying Amount	5,471	6,728
Residential Mortgage | Advances and other receivables, net
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Assets	552	628
Reverse Secured Borrowings, Assets, Carrying Amount	0	0
Residential Mortgage | Mortgage loans held for investment, net
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Assets	0	118
Reverse Secured Borrowings, Assets, Carrying Amount	0	0
Residential Mortgage | Advance facilities
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Liabilities	449	505
Reverse Secured Borrowings, Liabilities, Carrying Amount	0	0
Residential Mortgage | Payables and other liabilities
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Liabilities	1	1
Reverse Secured Borrowings, Liabilities, Carrying Amount	1	1
Residential Mortgage | Participating interest financing
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Liabilities	0	0
Reverse Secured Borrowings, Liabilities, Carrying Amount	4,581	5,607
Residential Mortgage | Trust 2017-2 | Other non-recourse debt
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Liabilities	0	0
Reverse Secured Borrowings, Liabilities, Carrying Amount	0	231
Residential Mortgage | Trust 2018-1 | Other non-recourse debt
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Liabilities	0	0
Reverse Secured Borrowings, Liabilities, Carrying Amount	201	284
Residential Mortgage | Trust 2018-2 | Other non-recourse debt
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Liabilities	0	0
Reverse Secured Borrowings, Liabilities, Carrying Amount	161	250
Residential Mortgage | Trust 2018-3 | Other non-recourse debt
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Liabilities	0	0
Reverse Secured Borrowings, Liabilities, Carrying Amount	239	326
Residential Mortgage | Trust 2019-1 | Other non-recourse debt
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Liabilities	0	0
Reverse Secured Borrowings, Liabilities, Carrying Amount	339	0
Residential Mortgage | Other nonrecourse debt
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Liabilities	0	29
Reverse Secured Borrowings, Liabilities, Carrying Amount	$ 0	$ 0