Reverse Mortgage Interests, Net - Purchase Discount Rollforward (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Purchase discount, net, for reverse mortgage interests
Balance - beginning of period	$ (127)	$ (163)	$ (114)	$ (164)
Adjustments	0	0	0	(24)
Utilization of purchase discounts	8	40	27	80
Amortization, net of accretion	(6)	(1)	(38)	(16)
Balance - end of period	$ (125)	$ (124)	$ (125)	$ (124)