Reverse Mortgage Interests, Net - Schedule of Reverse Mortgage Interest (Details) - USD ($) $ in Millions	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Reverse Mortgage Interests [Abstract]
Participating interests in HECM mortgage-backed securities (“HMBS”)	$ 3,663		$ 4,282
Other interests securitized	1,002		994
Unsecuritized interests	920		1,117
Purchase discount, net	(125)	$ (127)	(114)	$ (124)	$ (163)	$ (164)
Total reverse mortgage interests, net	$ 5,460		$ 6,279