Expected Losses to be Paid (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended					3 Months Ended				9 Months Ended				3 Months Ended				9 Months Ended				3 Months Ended				9 Months Ended				3 Months Ended				9 Months Ended				3 Months Ended				9 Months Ended				3 Months Ended				9 Months Ended				3 Months Ended				9 Months Ended				3 Months Ended				9 Months Ended				3 Months Ended				9 Months Ended				3 Months Ended				9 Months Ended				3 Months Ended				9 Months Ended				3 Months Ended				9 Months Ended				3 Months Ended				9 Months Ended				3 Months Ended				9 Months Ended					12 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012		Dec. 31, 2012	Sep. 30, 2013 Prime first lien		Sep. 30, 2012 Prime first lien		Sep. 30, 2013 Prime first lien		Sep. 30, 2012 Prime first lien		Sep. 30, 2013 Alt-A first lien		Sep. 30, 2012 Alt-A first lien		Sep. 30, 2013 Alt-A first lien		Sep. 30, 2012 Alt-A first lien		Sep. 30, 2013 Option ARM		Sep. 30, 2012 Option ARM		Sep. 30, 2013 Option ARM		Sep. 30, 2012 Option ARM		Sep. 30, 2013 First mortgage, subprime		Sep. 30, 2012 First mortgage, subprime		Sep. 30, 2013 First mortgage, subprime		Sep. 30, 2012 First mortgage, subprime		Sep. 30, 2013 Total first lien		Sep. 30, 2012 Total first lien		Sep. 30, 2013 Total first lien		Sep. 30, 2012 Total first lien		Sep. 30, 2013 Close ended second lien		Sep. 30, 2012 Close ended second lien		Sep. 30, 2013 Close ended second lien		Sep. 30, 2012 Close ended second lien		Sep. 30, 2013 HELOCs		Sep. 30, 2012 HELOCs		Sep. 30, 2013 HELOCs		Sep. 30, 2012 HELOCs		Sep. 30, 2013 Second lien		Sep. 30, 2012 Second lien		Sep. 30, 2013 Second lien		Sep. 30, 2012 Second lien		Sep. 30, 2013 U.S. RMBS		Sep. 30, 2012 U.S. RMBS		Sep. 30, 2013 U.S. RMBS		Sep. 30, 2012 U.S. RMBS		Sep. 30, 2013 TruPS		Sep. 30, 2012 TruPS		Sep. 30, 2013 TruPS		Sep. 30, 2012 TruPS		Sep. 30, 2013 Other structured finance		Sep. 30, 2012 Other structured finance		Sep. 30, 2013 Other structured finance		Sep. 30, 2012 Other structured finance		Sep. 30, 2013 US Public Finance		Sep. 30, 2012 US Public Finance		Sep. 30, 2013 US Public Finance		Sep. 30, 2012 US Public Finance		Sep. 30, 2013 Public finance Non-U.S.		Sep. 30, 2012 Public finance Non-U.S.		Sep. 30, 2013 Public finance Non-U.S.		Sep. 30, 2012 Public finance Non-U.S.		Sep. 30, 2013 Other		Sep. 30, 2012 Other		Sep. 30, 2013 Other		Sep. 30, 2012 Other		Sep. 30, 2013 Minimum	Dec. 31, 2012 Minimum	Sep. 30, 2013 Maximum	Dec. 31, 2012 Maximum
Guarantor Obligations [Line Items]
Discount factor (as a percent)																																																																																																																										0.00%	0.00%	4.36%	3.28%
Present Value of Net Expected Loss and Loss Adjustment Expenses to be Paid [Roll Forward]
Beginning of Period, Net Expected Loss to be Paid After Recoveries for R&W	$ 774		$ 1,198		$ 677	[1]	$ 1,106			$ 18		$ 4		$ 6	[1]	$ 2		$ 288		$ 321		$ 315	[1]	$ 295		$ (20)		$ 3		$ (131)	[1]	$ 210		$ 274		$ 236		$ 242	[1]	$ 241		$ 560		$ 564		$ 432	[1]	$ 748		$ (14)		$ (29)		$ (39)	[1]	$ (86)		$ (97)		$ (64)		$ (111)	[1]	$ (31)		$ (111)		$ (93)		$ (150)	[1]	$ (117)		$ 449		$ 471		$ 282	[1]	$ 631		$ 33		$ 50		$ 27	[1]	$ 64		$ 158		$ 320		$ 312	[1]	$ 342		$ 71		$ 59		$ 7	[1]	$ 16		$ 66		$ 302		$ 52	[1]	$ 51		$ (3)		$ (4)		$ (3)	[1]	$ 2
Net Expected Loss Development After Recoveries for R&W	(22)		64		(33)		365			3		1		16		3		(85)		14		(83)		27		25		3		(92)		12		38		13		86		39		(19)		31		(73)		81		0		4		7		0		(42)		(13)		(76)		9		(42)		(9)		(69)		9		(61)		22		(142)		90		9		5		7		(6)		(13)		(3)		(39)		7		44		7		138		65		(1)		33		13		215		0		0		(10)		(6)
(Paid) Recovered Losses	54	[2]	(509)	[2]	162	[2]	(718)	[2]		0	[2]	0	[2]	(1)	[2]	0	[2]	3	[2]	(24)	[2]	(26)	[2]	(11)	[2]	2	[2]	(96)	[2]	230	[2]	(312)	[2]	(9)	[2]	(10)	[2]	(25)	[2]	(41)	[2]	(4)	[2]	(130)	[2]	178	[2]	(364)	[2]	1	[2]	0	[2]	19	[2]	61	[2]	10	[2]	(30)	[2]	58	[2]	(85)	[2]	11	[2]	(30)	[2]	77	[2]	(24)	[2]	7	[2]	(160)	[2]	255	[2]	(388)	[2]	8	[2]	(2)	[2]	16	[2]	(5)	[2]	(17)	[2]	(2)	[2]	(145)	[2]	(34)	[2]	68	[2]	(56)	[2]	38	[2]	(71)	[2]	(12)	[2]	(289)	[2]	(12)	[2]	(220)	[2]	0	[2]	0	[2]	10	[2]	0	[2]
End of Period, Net Expected Loss to be Paid After Recoveries for R&W	806	[1]	753	[1]	806	[1]	753	[1]		21	[1]	5	[1]	21	[1]	5	[1]	206	[1]	311	[1]	206	[1]	311	[1]	7	[1]	(90)	[1]	7	[1]	(90)	[1]	303	[1]	239	[1]	303	[1]	239	[1]	537	[1]	465	[1]	537	[1]	465	[1]	(13)	[1]	(25)	[1]	(13)	[1]	(25)	[1]	(129)	[1]	(107)	[1]	(129)	[1]	(107)	[1]	(142)	[1]	(132)	[1]	(142)	[1]	(132)	[1]	395	[1]	333	[1]	395	[1]	333	[1]	50	[1]	53	[1]	50	[1]	53	[1]	128	[1]	315	[1]	128	[1]	315	[1]	183	[1]	10	[1]	183	[1]	10	[1]	53	[1]	46	[1]	53	[1]	46	[1]	(3)	[1]	(4)	[1]	(3)	[1]	(4)	[1]
Period after the end of the reporting period within which the ceded paid losses are typically settled (in days)	45 days				45 days
Expected LAE for mitigating claim liabilities	34				34				39
LAE paid	$ 12		$ 14		$ 41		$ 33

[1] Includes net expected loss adjustment expenses ("LAE") to be paid for mitigating claim liabilities of $34 million as of September 30, 2013 and $39 million as of December 31, 2012. The Company paid $12 million and $14 million in LAE for Third Quarter 2013 and 2012, respectively, and $41 million and $33 million in LAE for Nine Months 2013 and 2012, respectively.

[2] Net of ceded paid losses, whether or not such amounts have been settled with reinsurers. Ceded paid losses are typically settled 45 days after the end of the reporting period. Such amounts are recorded in reinsurance recoverable on paid losses included in other assets.