Expected Losses to be Paid - Net Expected Loss to be Paid by Accounting Model (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013		Jun. 30, 2014	Dec. 31, 2013		Jun. 30, 2013	Dec. 31, 2012
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W excluding other lines of business	$ 937				$ 937					$ 985
Net expected loss to be paid after recoveries for R&W	933	[1]	806		933	[1]	806		1,035	982	[1]	774	677
Net economic loss development (benefit)	(63)		(22)		(27)		(23)
Net expected loss development after recoveries for R&W	(63)		(22)		(28)		(33)
Financial guaranty insurance
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W	732				732					741
Net economic loss development (benefit)	(50)		(25)		(37)		(27)
Financial guaranty, variable interest entities
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W	122	[2]			122	[2]				60	[2]
Net economic loss development (benefit)	21	[2]	14	[2]	75	[2]	(18)	[2]
Credit derivatives
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W excluding other lines of business	83	[3]			83	[3]				184	[3]
Net economic loss development (benefit)	(34)	[4]	(11)	[4]	(65)	[4]	22	[4]
Prime first lien
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W excluding other lines of business	10				10					21
Net expected loss to be paid after recoveries for R&W	10	[1]	21		10	[1]	21		11	21	[1]	18	6
Net economic loss development (benefit)	(1)		3		(11)		16
Net expected loss development after recoveries for R&W	(1)		3		(11)		16
Prime first lien | Financial guaranty insurance
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W	3				3					3
Net economic loss development (benefit)	(1)		0		0		(1)
Prime first lien | Financial guaranty, variable interest entities
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W	0	[2]			0	[2]				0	[2]
Net economic loss development (benefit)	0	[2]	0	[2]	0	[2]	0	[2]
Prime first lien | Credit derivatives
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W excluding other lines of business	7				7					18
Net economic loss development (benefit)	0	[4]	3	[4]	(11)	[4]	17	[4]
Alt-A first lien
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W excluding other lines of business	248				248					304
Net expected loss to be paid after recoveries for R&W	248	[1]	206		248	[1]	206		301	304	[1]	288	315
Net economic loss development (benefit)	(18)		(85)		(6)		(83)
Net expected loss development after recoveries for R&W	(18)		(85)		(6)		(83)
Alt-A first lien | Financial guaranty insurance
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W	211				211					199
Net economic loss development (benefit)	6		(53)		32		(60)
Alt-A first lien | Financial guaranty, variable interest entities
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W	19	[2]			19	[2]				31	[2]
Net economic loss development (benefit)	(2)	[2]	3	[2]	(12)	[2]	3	[2]
Alt-A first lien | Credit derivatives
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W excluding other lines of business	18				18					74
Net economic loss development (benefit)	(22)	[4]	(35)	[4]	(26)	[4]	(26)	[4]
Option ARM
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W excluding other lines of business	(31)				(31)					(9)
Net expected loss to be paid after recoveries for R&W	(31)	[1]	7		(31)	[1]	7		(51)	(9)	[1]	(20)	(131)
Net economic loss development (benefit)	0		25		(39)		(92)
Net expected loss development after recoveries for R&W	0		25		(39)		(92)
Option ARM | Financial guaranty insurance
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W	(34)				(34)					(18)
Net economic loss development (benefit)	7		20		(32)		(58)
Option ARM | Financial guaranty, variable interest entities
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W	0	[2]			0	[2]				(2)	[2]
Net economic loss development (benefit)	0	[2]	1	[2]	1	[2]	(32)	[2]
Option ARM | Credit derivatives
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W excluding other lines of business	3				3					11
Net economic loss development (benefit)	(7)	[4]	4	[4]	(8)	[4]	(2)	[4]
First mortgage, subprime
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W excluding other lines of business	307				307					304
Net expected loss to be paid after recoveries for R&W	307	[1]	303		307	[1]	303		341	304	[1]	274	242
Net economic loss development (benefit)	(11)		38		(12)		86
Net expected loss development after recoveries for R&W	(11)		38		(12)		86
First mortgage, subprime | Financial guaranty insurance
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W	155				155					149
Net economic loss development (benefit)	(21)		25		(25)		40
First mortgage, subprime | Financial guaranty, variable interest entities
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W	78	[2]			78	[2]				81	[2]
Net economic loss development (benefit)	8	[2]	5	[2]	9	[2]	25	[2]
First mortgage, subprime | Credit derivatives
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W excluding other lines of business	74				74					74
Net economic loss development (benefit)	2	[4]	8	[4]	4	[4]	21	[4]
Total first lien
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W excluding other lines of business	534				534					620
Net expected loss to be paid after recoveries for R&W	534	[1]	537		534	[1]	537		602	620	[1]	560	432
Net economic loss development (benefit)	(30)		(19)		(68)		(73)
Net expected loss development after recoveries for R&W	(30)		(19)		(68)		(73)
Total first lien | Financial guaranty insurance
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W	335				335					333
Net economic loss development (benefit)	(9)		(8)		(25)		(79)
Total first lien | Financial guaranty, variable interest entities
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W	97	[2]			97	[2]				110	[2]
Net economic loss development (benefit)	6	[2]	9	[2]	(2)	[2]	(4)	[2]
Total first lien | Credit derivatives
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W excluding other lines of business	102				102					177
Net economic loss development (benefit)	(27)	[4]	(20)	[4]	(41)	[4]	10	[4]
Close ended second lien
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W excluding other lines of business	(5)				(5)					(11)
Net expected loss to be paid after recoveries for R&W	(5)	[1]	(13)		(5)	[1]	(13)		(9)	(11)	[1]	(14)	(39)
Net economic loss development (benefit)	2		0		2		7
Net expected loss development after recoveries for R&W	2		0		2		7
Close ended second lien | Financial guaranty insurance
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W	(28)				(28)					(34)
Net economic loss development (benefit)	2		2		0		0
Close ended second lien | Financial guaranty, variable interest entities
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W	28	[2]			28	[2]				25	[2]
Net economic loss development (benefit)	1	[2]	(3)	[2]	4	[2]	(4)	[2]
Close ended second lien | Credit derivatives
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W excluding other lines of business	(5)				(5)					(2)
Net economic loss development (benefit)	(1)	[4]	1	[4]	(2)	[4]	11	[4]
HELOCs
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W excluding other lines of business	(148)				(148)					(116)
Net expected loss to be paid after recoveries for R&W	(148)	[1]	(129)		(148)	[1]	(129)		(117)	(116)	[1]	(97)	(111)
Net economic loss development (benefit)	(34)		(42)		(65)		(76)
Net expected loss development after recoveries for R&W	(34)		(42)		(65)		(76)
HELOCs | Financial guaranty insurance
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W	(145)				(145)					(41)
Net economic loss development (benefit)	(48)		(49)		(138)		(66)
HELOCs | Financial guaranty, variable interest entities
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W	(3)	[2]			(3)	[2]				(75)	[2]
Net economic loss development (benefit)	14	[2]	8	[2]	73	[2]	(10)	[2]
HELOCs | Credit derivatives
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W excluding other lines of business	0				0					0
Net economic loss development (benefit)	0	[4]	(1)	[4]	0	[4]	0	[4]
Second lien
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W excluding other lines of business	(153)				(153)					(127)
Net expected loss to be paid after recoveries for R&W	(153)	[1]	(142)		(153)	[1]	(142)		(126)	(127)	[1]	(111)	(150)
Net economic loss development (benefit)	(32)		(42)		(63)		(69)
Net expected loss development after recoveries for R&W	(32)		(42)		(63)		(69)
Second lien | Financial guaranty insurance
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W	(173)				(173)					(75)
Net economic loss development (benefit)	(46)		(47)		(138)		(66)
Second lien | Financial guaranty, variable interest entities
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W	25	[2]			25	[2]				(50)	[2]
Net economic loss development (benefit)	15	[2]	5	[2]	77	[2]	(14)	[2]
Second lien | Credit derivatives
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W excluding other lines of business	(5)				(5)					(2)
Net economic loss development (benefit)	(1)	[4]	0	[4]	(2)	[4]	11	[4]
U.S. RMBS
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W excluding other lines of business	381				381					493
Net expected loss to be paid after recoveries for R&W	381	[1]	395		381	[1]	395		476	493	[1]	449	282
Net economic loss development (benefit)	(62)		(61)		(131)		(142)
Net expected loss development after recoveries for R&W	(62)		(61)		(131)		(142)
U.S. RMBS | Financial guaranty insurance
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W	162				162					258
Net economic loss development (benefit)	(55)		(55)		(163)		(145)
U.S. RMBS | Financial guaranty, variable interest entities
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W	122	[2]			122	[2]				60	[2]
Net economic loss development (benefit)	21	[2]	14	[2]	75	[2]	(18)	[2]
U.S. RMBS | Credit derivatives
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W excluding other lines of business	97	[3]			97	[3]				175	[3]
Net economic loss development (benefit)	(28)	[4]	(20)	[4]	(43)	[4]	21	[4]
TruPS
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W excluding other lines of business	26				26					51
Net expected loss to be paid after recoveries for R&W	26	[1]	50		26	[1]	50		32	51	[1]	33	27
Net economic loss development (benefit)	(5)		9		(24)		7
Net expected loss development after recoveries for R&W	(5)		9		(24)		7
TruPS | Financial guaranty insurance
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W	1				1					3
Net economic loss development (benefit)	(1)		1		(2)		1
TruPS | Financial guaranty, variable interest entities
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W	0	[2]			0	[2]				0	[2]
Net economic loss development (benefit)	0	[2]	0	[2]	0	[2]	0	[2]
TruPS | Credit derivatives
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W excluding other lines of business	25				25					48
Net economic loss development (benefit)	(4)	[4]	8	[4]	(22)	[4]	6	[4]
Structured finance
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W excluding other lines of business	146				146					120
Net expected loss to be paid after recoveries for R&W	146	[1]	128		146	[1]	128		140	120	[1]	158	312
Net economic loss development (benefit)	3		(13)		27		(39)
Net expected loss development after recoveries for R&W	3		(13)		27		(39)
Structured finance | Financial guaranty insurance
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W	186				186					161
Net economic loss development (benefit)	5		(13)		26		(32)
Structured finance | Financial guaranty, variable interest entities
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W	0	[2]			0	[2]				0	[2]
Net economic loss development (benefit)	0	[2]	0	[2]	0	[2]	0	[2]
Structured finance | Credit derivatives
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W excluding other lines of business	(40)				(40)					(41)
Net economic loss development (benefit)	(2)	[4]	0	[4]	1	[4]	(7)	[4]
Public Finance U.S.
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W excluding other lines of business	333				333					264
Net expected loss to be paid after recoveries for R&W	333	[1]	183		333	[1]	183		339	264	[1]	71	7
Net economic loss development (benefit)	2		44		107		138
Net expected loss development after recoveries for R&W	2		44		107		138
Public Finance U.S. | Financial guaranty insurance
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W	333				333					264
Net economic loss development (benefit)	2		43		107		137
Public Finance U.S. | Financial guaranty, variable interest entities
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W	0	[2]			0	[2]				0	[2]
Net economic loss development (benefit)	0	[2]	0	[2]	0	[2]	0	[2]
Public Finance U.S. | Credit derivatives
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W excluding other lines of business	0				0					0
Net economic loss development (benefit)	0	[4]	1	[4]	0	[4]	1	[4]
Public Finance Non-U.S.
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W excluding other lines of business	51				51					57
Net expected loss to be paid after recoveries for R&W	51	[1]	53		51	[1]	53		52	57	[1]	66	52
Net economic loss development (benefit)	(1)		(1)		(6)		13
Net expected loss development after recoveries for R&W	(1)		(1)		(6)		13
Public Finance Non-U.S. | Financial guaranty insurance
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W	50				50					55
Net economic loss development (benefit)	(1)		(1)		(5)		12
Public Finance Non-U.S. | Financial guaranty, variable interest entities
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W	0	[2]			0	[2]				0	[2]
Net economic loss development (benefit)	0	[2]	0	[2]	0	[2]	0	[2]
Public Finance Non-U.S. | Credit derivatives
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W excluding other lines of business	1				1					2
Net economic loss development (benefit)	0	[4]	0	[4]	(1)	[4]	1	[4]
Other
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W	(4)				(4)					(3)
Net expected loss development after recoveries for R&W	$ 0		$ 0		$ (1)		$ (10)

[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] Refer to Note 9, Consolidated Variable Interest Entities.

[3] Includes R&W benefit of $99 million as of September 30, 2014 and $180 million as of December 31, 2013.

[4] Refer to Note 8, Financial Guaranty Contracts Accounted for as Credit Derivatives.