Reverse Mortgage Interests, Net - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Aug. 01, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair Value	$ 25		$ 25		$ 22
Purchase discount	59		59		$ 46
Interest earned on HECM loans			117	$ 167
Unsecuritized HECM
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest earned on HECM loans	$ 55	$ 85
Participating Interests in HMBS
Accounts, Notes, Loans and Financing Receivable [Line Items]
UPB securitized			95	149
Government National Mortgage Association (GNMA) Insured Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
UPB securitized				61
Trust 2019-1
Accounts, Notes, Loans and Financing Receivable [Line Items]
UPB securitized				398
Trust 2017-2
Accounts, Notes, Loans and Financing Receivable [Line Items]
UPB called				249
Trust 2018-3
Accounts, Notes, Loans and Financing Receivable [Line Items]
UPB sold				20
Reverse mortgage interests, unsecuritized | HECM
Accounts, Notes, Loans and Financing Receivable [Line Items]
Repurchase of HECM loans			686	1,457
Repurchase of HECM loans funded by prior servicer			186	371
Housing and urban development, home equity conversion mortgage loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unsecuritized interests			$ 461	$ 983
Mortgage-backed debt
Accounts, Notes, Loans and Financing Receivable [Line Items]
Debt premium						$ 256