Expected Loss to be Paid - Net Expected Recoveries from Breaches of R&W Rollforward (Details) (RMBS [Member], United States [Member], USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014
Estimated Benefit From Recoveries From Breaches of R and W Net of Reinsurance [Roll Forward]
Future net R&W benefit at the beginning of the period	$ 317		$ 712
R&W development and accretion of discount during period	(51)		48
R&W recovered during period	(21)		(39)
Future net R&W benefit at the end of the period	245	[1]	721	[1]
First Lien [Member]
Estimated Benefit From Recoveries From Breaches of R and W Net of Reinsurance [Roll Forward]
Future net R&W benefit at the beginning of the period	232		569
R&W development and accretion of discount during period	(50)		39
R&W recovered during period	(20)		(38)
Future net R&W benefit at the end of the period	162	[1]	570	[1]
First Lien [Member] | Prime [Member]
Estimated Benefit From Recoveries From Breaches of R and W Net of Reinsurance [Roll Forward]
Future net R&W benefit at the beginning of the period	2		4
R&W development and accretion of discount during period	(1)		(1)
R&W recovered during period	0		0
Future net R&W benefit at the end of the period	1	[1]	3	[1]
First Lien [Member] | Alt-A [Member]
Estimated Benefit From Recoveries From Breaches of R and W Net of Reinsurance [Roll Forward]
Future net R&W benefit at the beginning of the period	106		274
R&W development and accretion of discount during period	(10)		3
R&W recovered during period	(2)		(8)
Future net R&W benefit at the end of the period	94	[1]	269	[1]
First Lien [Member] | Option ARM [Member]
Estimated Benefit From Recoveries From Breaches of R and W Net of Reinsurance [Roll Forward]
Future net R&W benefit at the beginning of the period	15		173
R&W development and accretion of discount during period	(20)		9
R&W recovered during period	(15)		(30)
Future net R&W benefit at the end of the period	(20)	[1]	152	[1]
First Lien [Member] | Subprime [Member]
Estimated Benefit From Recoveries From Breaches of R and W Net of Reinsurance [Roll Forward]
Future net R&W benefit at the beginning of the period	109		118
R&W development and accretion of discount during period	(19)		28
R&W recovered during period	(3)		0
Future net R&W benefit at the end of the period	87	[1]	146	[1]
Second Lien [Member]
Estimated Benefit From Recoveries From Breaches of R and W Net of Reinsurance [Roll Forward]
Future net R&W benefit at the beginning of the period	85		143
R&W development and accretion of discount during period	(1)		9
R&W recovered during period	(1)		(1)
Future net R&W benefit at the end of the period	83	[1]	151	[1]
Second Lien [Member] | Closed-end [Member]
Estimated Benefit From Recoveries From Breaches of R and W Net of Reinsurance [Roll Forward]
Future net R&W benefit at the beginning of the period	85		98
R&W development and accretion of discount during period	(1)		(3)
R&W recovered during period	(1)		0
Future net R&W benefit at the end of the period	83	[1]	95	[1]
Second Lien [Member] | HELOCs [Member]
Estimated Benefit From Recoveries From Breaches of R and W Net of Reinsurance [Roll Forward]
Future net R&W benefit at the beginning of the period	0		45
R&W development and accretion of discount during period	0		12
R&W recovered during period	0		(1)
Future net R&W benefit at the end of the period	$ 0	[1]	$ 56	[1]

[1] See the section "Breaches of Representations and Warranties" below for eligible assets held in trust.