Reverse Mortgage Interests, Net - Reserves Roll Forward (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Reverse Mortgage Interests Reserves [Roll Forward]
Balance - beginning of period	$ 8	$ 134	$ 13	$ 115
Provision (release), net	2	(6)	2	20
Write-offs	(2)	(11)	(7)	(18)
Balance - end of period	$ 8	$ 117	$ 8	$ 117