Reverse Mortgage Interests, Net - Purchase Discount Rollforward (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Net Discount for Other Interest Securitized
Balance - beginning of period	$ (100)
Adjustments	(2)
Utilization of purchase discounts	6
Accretion	(15)
Transfers	(1)
Balance - end of period	(112)
Net Discount for Unsecuritized Interests
Balance - beginning of period	(122)
Additions	(6)
Utilization of purchase discounts	22
Accretion	18
Transfers	(7)
Balance - end of period	(95)
Mortgage-backed debt
Net Premium for Participating Interests in HMBS(1)
Balance - beginning of period	58
Balance - end of period	36
Participating Interests in HMBS | Mortgage-backed debt
Net Premium for Participating Interests in HMBS(1)
Balance - beginning of period	58
Adjustments	(16)
Utilization of purchase discounts	0
Amortization	(14)
Transfers	8
Balance - end of period	$ 36
Predecessor
Purchase discounts for reverse mortgage interests
Balance - beginning of period		$ 89
Additions		(7)
Accretion		6
Balance - end of period		$ 90