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				6 Months Ended					3 Months Ended	6 Months Ended	3 Months Ended				6 Months Ended				3 Months Ended				6 Months Ended				3 Months Ended				6 Months Ended				3 Months Ended				6 Months Ended				3 Months Ended				6 Months Ended				3 Months Ended				6 Months Ended				3 Months Ended				6 Months Ended				3 Months Ended				6 Months Ended				3 Months Ended				6 Months Ended				3 Months Ended				6 Months Ended				3 Months Ended				6 Months Ended				3 Months Ended				6 Months Ended				3 Months Ended				6 Months Ended				3 Months Ended				6 Months Ended					12 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013		Dec. 31, 2013	Jun. 30, 2014 Spanish and Hungarian Debt [Member]	Jun. 30, 2014 Spanish and Hungarian Debt [Member]	Jun. 30, 2014 Prime first lien		Jun. 30, 2013 Prime first lien		Jun. 30, 2014 Prime first lien		Jun. 30, 2013 Prime first lien		Jun. 30, 2014 Alt-A first lien		Jun. 30, 2013 Alt-A first lien		Jun. 30, 2014 Alt-A first lien		Jun. 30, 2013 Alt-A first lien		Jun. 30, 2014 Option ARM		Jun. 30, 2013 Option ARM		Jun. 30, 2014 Option ARM		Jun. 30, 2013 Option ARM		Jun. 30, 2014 First mortgage, subprime		Jun. 30, 2013 First mortgage, subprime		Jun. 30, 2014 First mortgage, subprime		Jun. 30, 2013 First mortgage, subprime		Jun. 30, 2014 Total first lien		Jun. 30, 2013 Total first lien		Jun. 30, 2014 Total first lien		Jun. 30, 2013 Total first lien		Jun. 30, 2014 Close ended second lien		Jun. 30, 2013 Close ended second lien		Jun. 30, 2014 Close ended second lien		Jun. 30, 2013 Close ended second lien		Jun. 30, 2014 HELOCs		Jun. 30, 2013 HELOCs		Jun. 30, 2014 HELOCs		Jun. 30, 2013 HELOCs		Jun. 30, 2014 Second lien		Jun. 30, 2013 Second lien		Jun. 30, 2014 Second lien		Jun. 30, 2013 Second lien		Jun. 30, 2014 U.S. RMBS		Jun. 30, 2013 U.S. RMBS		Jun. 30, 2014 U.S. RMBS		Jun. 30, 2013 U.S. RMBS		Jun. 30, 2014 TruPS		Jun. 30, 2013 TruPS		Jun. 30, 2014 TruPS		Jun. 30, 2013 TruPS		Jun. 30, 2014 Structured finance		Jun. 30, 2013 Structured finance		Jun. 30, 2014 Structured finance		Jun. 30, 2013 Structured finance		Jun. 30, 2014 Public Finance U.S.		Jun. 30, 2013 Public Finance U.S.		Jun. 30, 2014 Public Finance U.S.		Jun. 30, 2013 Public Finance U.S.		Jun. 30, 2014 Public Finance Non-U.S.		Jun. 30, 2013 Public Finance Non-U.S.		Jun. 30, 2014 Public Finance Non-U.S.		Jun. 30, 2013 Public Finance Non-U.S.		Jun. 30, 2014 Other insurance		Jun. 30, 2013 Other insurance		Jun. 30, 2014 Other insurance		Jun. 30, 2013 Other insurance		Jun. 30, 2014 Minimum	Dec. 31, 2013 Minimum	Jun. 30, 2014 Maximum	Dec. 31, 2013 Maximum
Guarantor Obligations [Line Items]
Discount factor (as a percent)																																																																																																																												0.00%	0.00%	3.78%	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	$ 984	[1]	$ 487	[1]	$ 982	[1]	$ 677					$ 18	[1]	$ 11	[1]	$ 21	[1]	$ 6		$ 308	[1]	$ 313	[1]	$ 304	[1]	$ 315		$ (28)	[1]	$ (327)	[1]	$ (9)	[1]	$ (131)		$ 295	[1]	$ 263	[1]	$ 304	[1]	$ 242		$ 593	[1]	$ 260	[1]	$ 620	[1]	$ 432		$ (4)	[1]	$ (21)	[1]	$ (11)	[1]	$ (39)		$ (109)	[1]	$ (122)	[1]	$ (116)	[1]	$ (111)		$ (113)	[1]	$ (143)	[1]	$ (127)	[1]	$ (150)		$ 480	[1]	$ 117	[1]	$ 493	[1]	$ 282		$ 32	[1]	$ 23	[1]	$ 51	[1]	$ 27		$ 138	[1]	$ 307	[1]	$ 120	[1]	$ 312		$ 281	[1]	$ (9)	[1]	$ 264	[1]	$ 7		$ 57	[1]	$ 62	[1]	$ 57	[1]	$ 52		$ (4)	[1]	$ (13)	[1]	$ (3)	[1]	$ (3)
Net Expected Loss Development After Recoveries for R&W	23		87		35		(11)			1	1	(7)		7		(10)		13		4		(7)		12		2		(24)		21		(39)		(117)		6		23		(1)		48		(21)		44		(38)		(54)		(5)		6		0		7		(33)		(31)		(31)		(34)		(38)		(25)		(31)		(27)		(59)		19		(69)		(81)		0		1		(19)		(2)		5		(24)		24		(26)		82		87		105		94		(5)		4		(5)		14		0		0		(1)		(10)
(Paid) Recovered Losses	28	[2]	200	[2]	18	[2]	108	[2]				0	[2]	0	[2]	0	[2]	(1)	[2]	(11)	[2]	(18)	[2]	(15)	[2]	(29)	[2]	1	[2]	286	[2]	(3)	[2]	228	[2]	40	[2]	(12)	[2]	38	[2]	(16)	[2]	30	[2]	256	[2]	20	[2]	182	[2]	0	[2]	1	[2]	2	[2]	18	[2]	25	[2]	56	[2]	30	[2]	48	[2]	25	[2]	57	[2]	32	[2]	66	[2]	55	[2]	313	[2]	52	[2]	248	[2]	0	[2]	9	[2]	0	[2]	8	[2]	(3)	[2]	(125)	[2]	(4)	[2]	(128)	[2]	(24)	[2]	(7)	[2]	(30)	[2]	(30)	[2]	0	[2]	0	[2]	0	[2]	0	[2]	0	[2]	10	[2]	0	[2]	10	[2]
End of Period, Net Expected Loss to be Paid After Recoveries for R&W	1,035	[1]	774	[1]	1,035	[1]	774	[1]				11	[1]	18	[1]	11	[1]	18	[1]	301	[1]	288	[1]	301	[1]	288	[1]	(51)	[1]	(20)	[1]	(51)	[1]	(20)	[1]	341	[1]	274	[1]	341	[1]	274	[1]	602	[1]	560	[1]	602	[1]	560	[1]	(9)	[1]	(14)	[1]	(9)	[1]	(14)	[1]	(117)	[1]	(97)	[1]	(117)	[1]	(97)	[1]	(126)	[1]	(111)	[1]	(126)	[1]	(111)	[1]	476	[1]	449	[1]	476	[1]	449	[1]	32	[1]	33	[1]	32	[1]	33	[1]	140	[1]	158	[1]	140	[1]	158	[1]	339	[1]	71	[1]	339	[1]	71	[1]	52	[1]	66	[1]	52	[1]	66	[1]	(4)	[1]	(3)	[1]	(4)	[1]	(3)	[1]
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	33				33				34	50	50
LAE paid	$ 8		$ 16		$ 14		$ 29

[1] Includes expected loss adjustment expenses ("LAE") to be paid of $33 million as of June 30, 2014 and $34 million as of December 31, 2013. The Company paid $8 million and $16 million in LAE for Second Quarter 2014 and 2013, respectively, and $14 million and $29 million in LAE for Six Months 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.