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				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, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013		Dec. 31, 2013	Sep. 30, 2014 Spanish and Hungarian debt	Sep. 30, 2014 Prime first lien		Sep. 30, 2013 Prime first lien		Sep. 30, 2014 Prime first lien		Sep. 30, 2013 Prime first lien		Sep. 30, 2014 Alt-A first lien		Sep. 30, 2013 Alt-A first lien		Sep. 30, 2014 Alt-A first lien		Sep. 30, 2013 Alt-A first lien		Sep. 30, 2014 Option ARM		Sep. 30, 2013 Option ARM		Sep. 30, 2014 Option ARM		Sep. 30, 2013 Option ARM		Sep. 30, 2014 First mortgage, subprime		Sep. 30, 2013 First mortgage, subprime		Sep. 30, 2014 First mortgage, subprime		Sep. 30, 2013 First mortgage, subprime		Sep. 30, 2014 Total first lien		Sep. 30, 2013 Total first lien		Sep. 30, 2014 Total first lien		Sep. 30, 2013 Total first lien		Sep. 30, 2014 Close ended second lien		Sep. 30, 2013 Close ended second lien		Sep. 30, 2014 Close ended second lien		Sep. 30, 2013 Close ended second lien		Sep. 30, 2014 HELOCs		Sep. 30, 2013 HELOCs		Sep. 30, 2014 HELOCs		Sep. 30, 2013 HELOCs		Sep. 30, 2014 Second lien		Sep. 30, 2013 Second lien		Sep. 30, 2014 Second lien		Sep. 30, 2013 Second lien		Sep. 30, 2014 U.S. RMBS		Sep. 30, 2013 U.S. RMBS		Sep. 30, 2014 U.S. RMBS		Sep. 30, 2013 U.S. RMBS		Sep. 30, 2014 TruPS		Sep. 30, 2013 TruPS		Sep. 30, 2014 TruPS		Sep. 30, 2013 TruPS		Sep. 30, 2014 Structured finance		Sep. 30, 2013 Structured finance		Sep. 30, 2014 Structured finance		Sep. 30, 2013 Structured finance		Sep. 30, 2014 Public Finance U.S.		Sep. 30, 2013 Public Finance U.S.		Sep. 30, 2014 Public Finance U.S.		Sep. 30, 2013 Public Finance U.S.		Sep. 30, 2014 Public Finance Non-U.S.		Sep. 30, 2013 Public Finance Non-U.S.		Sep. 30, 2014 Public Finance Non-U.S.		Sep. 30, 2013 Public Finance Non-U.S.		Sep. 30, 2014 Other insurance		Sep. 30, 2013 Other insurance		Sep. 30, 2014 Other insurance		Sep. 30, 2013 Other insurance		Sep. 30, 2014 Minimum	Dec. 31, 2013 Minimum	Sep. 30, 2014 Maximum	Dec. 31, 2013 Maximum
Guarantor Obligations [Line Items]
Discount factor (as a percent)																																																																																																																											0.00%	0.00%	3.68%	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	$ 1,035		$ 774		$ 982	[1]	$ 677			$ 50	$ 11		$ 18		$ 21	[1]	$ 6		$ 301		$ 288		$ 304	[1]	$ 315		$ (51)		$ (20)		$ (9)	[1]	$ (131)		$ 341		$ 274		$ 304	[1]	$ 242		$ 602		$ 560		$ 620	[1]	$ 432		$ (9)		$ (14)		$ (11)	[1]	$ (39)		$ (117)		$ (97)		$ (116)	[1]	$ (111)		$ (126)		$ (111)		$ (127)	[1]	$ (150)		$ 476		$ 449		$ 493	[1]	$ 282		$ 32		$ 33		$ 51	[1]	$ 27		$ 140		$ 158		$ 120	[1]	$ 312		$ 339		$ 71		$ 264	[1]	$ 7		$ 52		$ 66		$ 57	[1]	$ 52		$ (4)		$ (3)		$ (3)	[1]	$ (3)
Net expected loss development after recoveries for R&W	(63)		(22)		(28)		(33)				(1)		3		(11)		16		(18)		(85)		(6)		(83)		0		25		(39)		(92)		(11)		38		(12)		86		(30)		(19)		(68)		(73)		2		0		2		7		(34)		(42)		(65)		(76)		(32)		(42)		(63)		(69)		(62)		(61)		(131)		(142)		(5)		9		(24)		7		3		(13)		27		(39)		2		44		107		138		(1)		(1)		(6)		13		0		0		(1)		(10)
(Paid) recovered losses	(39)	[2]	54	[2]	(21)	[2]	162	[2]			0	[2]	0	[2]	0	[2]	(1)	[2]	(35)	[2]	3	[2]	(50)	[2]	(26)	[2]	20	[2]	2	[2]	17	[2]	230	[2]	(23)	[2]	(9)	[2]	15	[2]	(25)	[2]	(38)	[2]	(4)	[2]	(18)	[2]	178	[2]	2	[2]	1	[2]	4	[2]	19	[2]	3	[2]	10	[2]	33	[2]	58	[2]	5	[2]	11	[2]	37	[2]	77	[2]	(33)	[2]	7	[2]	19	[2]	255	[2]	(1)	[2]	8	[2]	(1)	[2]	16	[2]	3	[2]	(17)	[2]	(1)	[2]	(145)	[2]	(8)	[2]	68	[2]	(38)	[2]	38	[2]	0	[2]	(12)	[2]	0	[2]	(12)	[2]	0	[2]	0	[2]	0	[2]	10	[2]
End of period, net expected loss to be paid after recoveries for R&W	933	[1]	806		933	[1]	806			50	10	[1]	21		10	[1]	21		248	[1]	206		248	[1]	206		(31)	[1]	7		(31)	[1]	7		307	[1]	303		307	[1]	303		534	[1]	537		534	[1]	537		(5)	[1]	(13)		(5)	[1]	(13)		(148)	[1]	(129)		(148)	[1]	(129)		(153)	[1]	(142)		(153)	[1]	(142)		381	[1]	395		381	[1]	395		26	[1]	50		26	[1]	50		146	[1]	128		146	[1]	128		333	[1]	183		333	[1]	183		51	[1]	53		51	[1]	53		(4)	[1]	(3)		(4)	[1]	(3)
Period after the end of the reporting period within which the ceded paid losses are typically settled (in days)					45 days
Expected loss adjustment expenses to be paid	28				28				34
Loss and loss adjustment expense reserve	760				760				592
Expected LAE for mitigating claim liabilities	24				24				27
LAE paid	$ 6		$ 12		$ 20		$ 41

[1] Includes expected loss adjustment expenses ("LAE") to be paid of $28 million as of September 30, 2014 and $34 million as of December 31, 2013. The Company paid $6 million and $12 million in LAE for Third Quarter 2014 and 2013, respectively, and $20 million and $41 million in LAE for Nine 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.