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, 2017
Discount for Other Interest Securitized
Balance - beginning of period	$ (117)
Additions	0
Utilization of purchase discounts	0
Accretion/(Amortization)	17
Balance - end of period	(100)	$ (117)
Discount for Unsecuritized Interests
Balance - beginning of period	(173)
Additions	0
Utilization of purchase discounts	43
Accretion/(Amortization)	8
Balance - end of period	(122)	(173)
Participating Interests in HMBS | Mortgage-backed debt
Premium for Participating Interests in HMBS
Balance - beginning of period	58
Additions	0
Utilization of purchase discounts	0
Accretion/(Amortization)	0
Balance - end of period	58	58
Predecessor
Premium for Participating Interests in HMBS
Balance - beginning of period		62
Balance - end of period			$ 62
Discount for Other Interest Securitized
Balance - beginning of period		0
Balance - end of period			0
Discount for Unsecuritized Interests
Balance - beginning of period		(89)
Balance - end of period			(89)
Purchase discounts for reverse mortgage interests
Balance - beginning of period	$ (82)	(89)	(43)
Additions		(7)	(75)
Accretion		14	29
Balance - end of period		$ (82)	$ (89)