Reverse Mortgage Interests, Net - Purchase Premiums and Discounts for Reverse Mortgages (Details) - USD ($) $ in Millions	5 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2019
Discount for Unsecuritized Interests
Balance - beginning of period	$ (117)	$ (100)
Adjustments		(2)
Utilization of purchase discounts	0	33
Accretion/(Amortization)	17	23
Transfers		(10)
Balance - end of period	(100)	(56)
Discount for Other Interest Securitized
Balance - beginning of period	(173)	(122)
Adjustments		(6)
Utilization of purchase discounts	43	63
Accretion/(Amortization)	8	4
Transfers		(7)
Balance - end of period	(122)	(68)
Mortgage-backed debt
Premium for Participating Interests in HMBS
Balance - beginning of period		58
Balance - end of period	58	10
Participating Interests in HMBS | Mortgage-backed debt
Premium for Participating Interests in HMBS
Balance - beginning of period	58	58
Adjustments		(16)
Utilization of purchase discounts	0	0
Accretion/(Amortization)	0	(49)
Transfers		17
Balance - end of period	$ 58	$ 10