Reverse Mortgage Interests, Net - Purchase Discount Rollforward (Details) - USD ($) $ in Millions	5 Months Ended	7 Months Ended	12 Months Ended
	Dec. 31, 2018	Jul. 31, 2018	Dec. 31, 2019
Discount for Other Interest Securitized
Balance - beginning of period	$ (117)		$ (100)
Utilization of purchase discounts	0		33
Accretion/(Amortization)	17		23
Balance - end of period	(100)	$ (117)	(56)
Discount for Unsecuritized Interests
Balance - beginning of period	(173)		(122)
Utilization of purchase discounts	43		63
Accretion/(Amortization)	8		4
Balance - end of period	(122)	(173)	(68)
Purchase discounts for reverse mortgage interests
Balance - beginning of period	(82)	(89)	(42)
Additions		(7)
Accretion		14
Balance - end of period	(42)	(82)	(46)
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
Utilization of purchase discounts	0		0
Accretion/(Amortization)	0		49
Balance - end of period	$ 58	$ 58	$ 10