Securitizations and Financings - Assets and Liabilities of Consolidated VIEs (Details) $ in Millions	3 Months Ended
	Mar. 31, 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	$ 820	$ 816
Reverse Secured Borrowings, Assets, Carrying Amount	6,368	6,833
Liabilities	515	535
Reverse Secured Borrowings, Liabilities, Carrying Amount	6,304	6,699
Residential Mortgage | Restricted cash
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Assets	98	70
Reverse Secured Borrowings, Assets, Carrying Amount	49	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	6,319	6,770
Residential Mortgage | Advances and other receivables, net
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Assets	605	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	117	118
Reverse Secured Borrowings, Assets, Carrying Amount	0	0
Residential Mortgage | Other assets
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Assets	0	0
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	488	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	5,319	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	207	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	252	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	213	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	312	326
Residential Mortgage | Other nonrecourse debt
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Liabilities	26	29
Reverse Secured Borrowings, Liabilities, Carrying Amount	$ 0	$ 0