Securitizations and Financings - Assets and Liabilities of Consolidated VIEs (Details) $ in Millions	Dec. 31, 2018 USD ($) special_purpose_entity	Dec. 31, 2017 USD ($)
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Consolidated reverse mortgage SPE's | special_purpose_entity	4
Transfers Accounted for as Secured Borrowings, Assets	$ 816
Reverse Secured Borrowings, Assets	6,833
Transfers Accounted for as Secured Borrowings, Liabilities	535
Reverse Secured Borrowings, Liabilities	6,699
Residential Mortgage | Restricted cash
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers Accounted for as Secured Borrowings, Assets	70
Reverse Secured Borrowings, Assets	63
Residential Mortgage | Reverse mortgage interests, net
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers Accounted for as Secured Borrowings, Assets	0
Reverse Secured Borrowings, Assets	6,770
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	628
Reverse Secured Borrowings, Assets	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	118
Reverse Secured Borrowings, Assets	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
Reverse Secured Borrowings, Assets	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	505
Reverse Secured Borrowings, Liabilities	0
Residential Mortgage | Payables and accrued liabilities
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers Accounted for as Secured Borrowings, Liabilities	1
Reverse Secured Borrowings, Liabilities	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
Reverse Secured Borrowings, Liabilities	5,607
Residential Mortgage | Trust 2016-2 | HECM Securitizations (HMBS)
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers Accounted for as Secured Borrowings, Liabilities	0
Reverse Secured Borrowings, Liabilities	0
Residential Mortgage | Trust 2016-3 | HECM Securitizations (HMBS)
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers Accounted for as Secured Borrowings, Liabilities	0
Reverse Secured Borrowings, Liabilities	0
Residential Mortgage | Trust 2017-1 | HECM Securitizations (HMBS)
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers Accounted for as Secured Borrowings, Liabilities	0
Reverse Secured Borrowings, Liabilities	0
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
Reverse Secured Borrowings, Liabilities	231
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
Reverse Secured Borrowings, Liabilities	284
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
Reverse Secured Borrowings, Liabilities	250
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
Reverse Secured Borrowings, Liabilities	326
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	29
Reverse Secured Borrowings, Liabilities	$ 0
Predecessor
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers Accounted for as Secured Borrowings, Assets		$ 1,142
Reverse Secured Borrowings, Assets		8,007
Transfers Accounted for as Secured Borrowings, Liabilities		793
Reverse Secured Borrowings, Liabilities		7,922
Predecessor | Residential Mortgage | Restricted cash
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers Accounted for as Secured Borrowings, Assets		106
Reverse Secured Borrowings, Assets		26
Predecessor | Residential Mortgage | Reverse mortgage interests, net
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers Accounted for as Secured Borrowings, Assets		0
Reverse Secured Borrowings, Assets		7,981
Predecessor | 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		896
Reverse Secured Borrowings, Assets		0
Predecessor | 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		138
Reverse Secured Borrowings, Assets		0
Predecessor | Residential Mortgage | Other assets
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers Accounted for as Secured Borrowings, Assets		2
Reverse Secured Borrowings, Assets		0
Predecessor | Residential Mortgage | Advance facilities
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers Accounted for as Secured Borrowings, Liabilities		749
Reverse Secured Borrowings, Liabilities		0
Predecessor | Residential Mortgage | Payables and accrued liabilities
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers Accounted for as Secured Borrowings, Liabilities		2
Reverse Secured Borrowings, Liabilities		1
Predecessor | 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
Reverse Secured Borrowings, Liabilities		7,111
Predecessor | Residential Mortgage | Trust 2016-2 | HECM Securitizations (HMBS)
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers Accounted for as Secured Borrowings, Liabilities		0
Reverse Secured Borrowings, Liabilities		94
Predecessor | Residential Mortgage | Trust 2016-3 | HECM Securitizations (HMBS)
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers Accounted for as Secured Borrowings, Liabilities		0
Reverse Secured Borrowings, Liabilities		138
Predecessor | Residential Mortgage | Trust 2017-1 | HECM Securitizations (HMBS)
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers Accounted for as Secured Borrowings, Liabilities		0
Reverse Secured Borrowings, Liabilities		213
Predecessor | 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
Reverse Secured Borrowings, Liabilities		365
Predecessor | 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
Reverse Secured Borrowings, Liabilities		0
Predecessor | 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
Reverse Secured Borrowings, Liabilities		0
Predecessor | 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
Reverse Secured Borrowings, Liabilities		0
Predecessor | 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		42
Reverse Secured Borrowings, Liabilities		$ 0