Reverse Mortgage Interests - Purchase Discount Rollforward (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Purchase discount, net, for reverse mortgage interests
Balance - beginning of year	$ (114)	$ (164)
Amortization, net of accretion	(44)	(22)
Utilization of purchase discounts	31	96
Adjustments	0	(24)
Balance - end of year	$ (127)	$ (114)