Reverse Mortgage Interests, Net - Purchase Discount Rollforward (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Purchase discount, net, for reverse mortgage interests
Balance - beginning of period	$ (127)	$ (163)	$ (127)	$ (163)
Adjustments(2)	0	0	0	(24)
Utilization of purchase discounts	9	12	19	40
Amortization, net of accretion	(7)	(4)	(32)	(15)
Balance - end of period	$ (129)	$ (171)	$ (114)	$ (164)