Expected Losses to be Paid - Net Expected Loss to be Paid Before Recoveries for Breaches of R&W Roll Forward by Sector (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended					3 Months Ended																																																									12 Months Ended	3 Months Ended	12 Months Ended
	Mar. 31, 2014		Mar. 31, 2013		Dec. 31, 2013	Mar. 31, 2014 Prime first lien		Mar. 31, 2013 Prime first lien		Mar. 31, 2014 Alt-A first lien		Mar. 31, 2013 Alt-A first lien		Mar. 31, 2014 Option ARM		Mar. 31, 2013 Option ARM		Mar. 31, 2014 First mortgage, subprime		Mar. 31, 2013 First mortgage, subprime		Mar. 31, 2014 Total first lien		Mar. 31, 2013 Total first lien		Mar. 31, 2014 Close ended second lien		Mar. 31, 2013 Close ended second lien		Mar. 31, 2014 HELOCs		Mar. 31, 2013 HELOCs		Mar. 31, 2014 Second lien		Mar. 31, 2013 Second lien		Mar. 31, 2014 U.S. RMBS		Mar. 31, 2013 U.S. RMBS		Mar. 31, 2014 TruPS		Mar. 31, 2013 TruPS		Mar. 31, 2014 Structured finance		Mar. 31, 2013 Structured finance		Mar. 31, 2014 Public Finance U.S.		Mar. 31, 2013 Public Finance U.S.		Mar. 31, 2014 Public Finance Non-U.S.		Mar. 31, 2013 Public Finance Non-U.S.		Mar. 31, 2014 Other		Mar. 31, 2013 Other		Mar. 31, 2014 Minimum	Dec. 31, 2013 Minimum	Mar. 31, 2014 Maximum	Dec. 31, 2013 Maximum
Guarantor Obligations [Line Items]
Discount factor (as a percent)																																																														0.00%	0.00%	3.97%	4.44%
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	$ 982	[1]	$ 677			$ 21	[1]	$ 6		$ 304	[1]	$ 315		$ (9)	[1]	$ (131)		$ 304	[1]	$ 242		$ 620	[1]	$ 432		$ (11)	[1]	$ (39)		$ (116)	[1]	$ (111)		$ (127)	[1]	$ (150)		$ 493	[1]	$ 282		$ 51	[1]	$ 27		$ 120	[1]	$ 312		$ 264	[1]	$ 7		$ 57	[1]	$ 52		$ (3)	[1]	$ (3)
Net Expected Loss Development After Recoveries for R&W	12		(98)			(3)		6		8		9		(15)		(138)		(7)		25		(17)		(98)		5		1		2		(3)		7		(2)		(10)		(100)		(19)		(3)		19		(2)		23		7		0		10		(1)		(10)
(Paid) Recovered Losses	(10)	[2]	(92)	[2]		0	[2]	(1)	[2]	(4)	[2]	(11)	[2]	(4)	[2]	(58)	[2]	(2)	[2]	(4)	[2]	(10)	[2]	(74)	[2]	2	[2]	17	[2]	5	[2]	(8)	[2]	7	[2]	9	[2]	(3)	[2]	(65)	[2]	0	[2]	(1)	[2]	(1)	[2]	(3)	[2]	(6)	[2]	(23)	[2]	0	[2]	0	[2]	0	[2]	0	[2]
End of Period, Net Expected Loss to be Paid After Recoveries for R&W	984	[1]	487			18	[1]	11		308	[1]	313		(28)	[1]	(327)		295	[1]	263		593	[1]	260		(4)	[1]	(21)		(109)	[1]	(122)		(113)	[1]	(143)		480	[1]	117		32	[1]	23		138	[1]	307		281	[1]	(9)		57	[1]	62		(4)	[1]	(13)
Period after the end of the reporting period within which the ceded paid losses are typically settled (in days)	45 days
Expected LAE for mitigating claim liabilities	29				34
LAE paid	$ 6		$ 13

[1] Includes expected loss adjustment expenses ("LAE") to be paid for mitigating claim liabilities of $29 million as of March 31, 2014 and $34 million as of December 31, 2013. The Company paid $6 million and $13 million in LAE for First Quarter 2014 and 2013, 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.