Expected Loss to be Paid - Net Expected Loss to be Paid and Net Economic Loss Development by Accounting Model (Details) - USD ($) $ in Millions		3 Months Ended			6 Months Ended
		Jun. 30, 2015		Jun. 30, 2014	Jun. 30, 2015		Jun. 30, 2014		Mar. 31, 2015	Dec. 31, 2014		Mar. 31, 2014	Dec. 31, 2013
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		$ 1,510	[1]	$ 1,035	$ 1,510	[1]	$ 1,035		$ 1,154	$ 1,169	[1]	$ 984	$ 982
Economic loss development after recoveries for R&W		192		23	189		35
Subtotal [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		1,510			1,510					1,169
Economic loss development after recoveries for R&W		192		23	189		35
Public Finance [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		657	[1]	391	657	[1]	391		352	348	[1]	338	321
Economic loss development after recoveries for R&W		224		77	230		100
Public Finance [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		613	[1]	339	613	[1]	339		310	303	[1]	281	264
Economic loss development after recoveries for R&W		226		82	235		105
Public Finance [Member] | Non United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		44	[1]	52	44	[1]	52		42	45	[1]	57	57
Economic loss development after recoveries for R&W		(2)		(5)	(5)		(5)
RMBS [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		524	[1]	476	524	[1]	476		570	584	[1]	480	493
Economic loss development after recoveries for R&W		(32)		(59)	(28)		(69)
RMBS [Member] | First Lien [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		521	[1]	602	521	[1]	602		569	595	[1]	593	620
Economic loss development after recoveries for R&W		(26)		(21)	(28)		(38)
RMBS [Member] | First Lien [Member] | Prime [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		1	[1]	11	1	[1]	11		3	4	[1]	18	21
Economic loss development after recoveries for R&W		(1)		(7)	(1)		(10)
RMBS [Member] | First Lien [Member] | Alt-A [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		265	[1]	301	265	[1]	301		289	304	[1]	308	304
Economic loss development after recoveries for R&W		(16)		4	(21)		12
RMBS [Member] | First Lien [Member] | Option ARM [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		(18)	[1]	(51)	(18)	[1]	(51)		(16)	(16)	[1]	(28)	(9)
Economic loss development after recoveries for R&W		(3)		(24)	1		(39)
RMBS [Member] | First Lien [Member] | Subprime [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		273	[1]	341	273	[1]	341		293	303	[1]	295	304
Economic loss development after recoveries for R&W		(6)		6	(7)		(1)
RMBS [Member] | Second Lien [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		3	[1]	(126)	3	[1]	(126)		1	(11)	[1]	(113)	(127)
Economic loss development after recoveries for R&W		(6)		(38)	0		(31)
RMBS [Member] | Second Lien [Member] | Closed-end [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		9	[1]	(9)	9	[1]	(9)		11	8	[1]	(4)	(11)
Economic loss development after recoveries for R&W		(3)		(5)	(2)		0
RMBS [Member] | Second Lien [Member] | HELOCs [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		(6)	[1]	(117)	(6)	[1]	(117)		(10)	(19)	[1]	(109)	(116)
Economic loss development after recoveries for R&W		(3)		(33)	2		(31)
Triple-X Life Insurance Transaction [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		165	[1]	87	165	[1]	87		165	161	[1]	87	75
Economic loss development after recoveries for R&W		2		1	7		14
Trust Preferred Securities (TruPS) [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		10	[1]	32	10	[1]	32		14	23	[1]	32	51
Economic loss development after recoveries for R&W		(4)		0	(13)		(19)	[2]
Student Loan [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		58	[1]	58	58	[1]	58		62	68	[1]	54	52
Economic loss development after recoveries for R&W		1		4	(5)		6	[2]
Other structured finance [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		96	[1]	(9)	96	[1]	(9)		(9)	(15)	[1]	(7)	(10)
Economic loss development after recoveries for R&W		1		0	(2)		3
Structured Finance [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		853	[1]	644	853	[1]	644		$ 802	821	[1]	$ 646	$ 661
Economic loss development after recoveries for R&W		(32)		(54)	(41)		(65)
Financial Guarantee Accounted for as Insurance Contracts [Member] | Subtotal [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		1,264			1,264					989
Economic loss development after recoveries for R&W		207		36	219		13
Financial Guarantee Accounted for as Insurance Contracts [Member] | Public Finance [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		657			657					348
Economic loss development after recoveries for R&W		230		78	236		101
Financial Guarantee Accounted for as Insurance Contracts [Member] | Public Finance [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		613			613					303
Economic loss development after recoveries for R&W		232		82	241		105
Financial Guarantee Accounted for as Insurance Contracts [Member] | Public Finance [Member] | Non United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		44			44					45
Economic loss development after recoveries for R&W		(2)		(4)	(5)		(4)
Financial Guarantee Accounted for as Insurance Contracts [Member] | RMBS [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		357			357					385
Economic loss development after recoveries for R&W		(24)		(46)	(16)		(108)
Financial Guarantee Accounted for as Insurance Contracts [Member] | RMBS [Member] | First Lien [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		394			394					438
Economic loss development after recoveries for R&W		(17)		(11)	(17)		(16)
Financial Guarantee Accounted for as Insurance Contracts [Member] | RMBS [Member] | First Lien [Member] | Prime [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		2			2					2
Economic loss development after recoveries for R&W		(1)		1	0		1
Financial Guarantee Accounted for as Insurance Contracts [Member] | RMBS [Member] | First Lien [Member] | Alt-A [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		261			261					288
Economic loss development after recoveries for R&W		(12)		7	(10)		26
Financial Guarantee Accounted for as Insurance Contracts [Member] | RMBS [Member] | First Lien [Member] | Option ARM [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		(20)			(20)					(15)
Economic loss development after recoveries for R&W		(4)		(23)	(3)		(39)
Financial Guarantee Accounted for as Insurance Contracts [Member] | RMBS [Member] | First Lien [Member] | Subprime [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		151			151					163
Economic loss development after recoveries for R&W		0		4	(4)		(4)
Financial Guarantee Accounted for as Insurance Contracts [Member] | RMBS [Member] | Second Lien [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		(37)			(37)					(53)
Economic loss development after recoveries for R&W		(7)		(35)	1		(92)
Financial Guarantee Accounted for as Insurance Contracts [Member] | RMBS [Member] | Second Lien [Member] | Closed-end [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		(25)			(25)					(27)
Economic loss development after recoveries for R&W		(2)		(1)	(1)		(2)
Financial Guarantee Accounted for as Insurance Contracts [Member] | RMBS [Member] | Second Lien [Member] | HELOCs [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		(12)			(12)					(26)
Economic loss development after recoveries for R&W		(5)		(34)	2		(90)
Financial Guarantee Accounted for as Insurance Contracts [Member] | Triple-X Life Insurance Transaction [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		157			157					153
Economic loss development after recoveries for R&W		1		0	5		13
Financial Guarantee Accounted for as Insurance Contracts [Member] | Trust Preferred Securities (TruPS) [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		0			0					1
Economic loss development after recoveries for R&W		0		0	(1)		(1)
Financial Guarantee Accounted for as Insurance Contracts [Member] | Student Loan [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		58			58					68
Economic loss development after recoveries for R&W		1		4	(5)		6
Financial Guarantee Accounted for as Insurance Contracts [Member] | Other structured finance [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		35			35					34
Economic loss development after recoveries for R&W		(1)		0	0		2
Financial Guarantee Accounted for as Insurance Contracts [Member] | Structured Finance [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		607			607					641
Economic loss development after recoveries for R&W		(23)		(42)	(17)		(88)
Financial Guaranty Variable Interest Entities and Other [Member] | Subtotal [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W	[3]	133			133					122
Economic loss development after recoveries for R&W	[4]	(1)		7	1		53
Financial Guaranty Variable Interest Entities and Other [Member] | Public Finance [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W	[3]	0			0					0
Economic loss development after recoveries for R&W	[4]	0		0	0		0
Financial Guaranty Variable Interest Entities and Other [Member] | Public Finance [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W	[3]	0			0					0
Economic loss development after recoveries for R&W	[4]	0		0	0		0
Financial Guaranty Variable Interest Entities and Other [Member] | Public Finance [Member] | Non United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W	[3]	0			0					0
Economic loss development after recoveries for R&W	[4]	0		0	0		0
Financial Guaranty Variable Interest Entities and Other [Member] | RMBS [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W	[3]	114			114					126
Economic loss development after recoveries for R&W	[4]	(2)		7	1		54
Financial Guaranty Variable Interest Entities and Other [Member] | RMBS [Member] | First Lien [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W	[3]	78			78					88
Economic loss development after recoveries for R&W	[4]	(2)		5	2		(8)
Financial Guaranty Variable Interest Entities and Other [Member] | RMBS [Member] | First Lien [Member] | Prime [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W	[3]	0			0					0
Economic loss development after recoveries for R&W	[4]	0		0	0		0
Financial Guaranty Variable Interest Entities and Other [Member] | RMBS [Member] | First Lien [Member] | Alt-A [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W	[3]	16			16					17
Economic loss development after recoveries for R&W	[4]	(1)		2	(1)		(10)
Financial Guaranty Variable Interest Entities and Other [Member] | RMBS [Member] | First Lien [Member] | Option ARM [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W	[3]	0			0					0
Economic loss development after recoveries for R&W	[4]	0		0	0		1
Financial Guaranty Variable Interest Entities and Other [Member] | RMBS [Member] | First Lien [Member] | Subprime [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W	[3]	62			62					71
Economic loss development after recoveries for R&W	[4]	(1)		3	3		1
Financial Guaranty Variable Interest Entities and Other [Member] | RMBS [Member] | Second Lien [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W	[3]	36			36					38
Economic loss development after recoveries for R&W	[4]	0		2	(1)		62
Financial Guaranty Variable Interest Entities and Other [Member] | RMBS [Member] | Second Lien [Member] | Closed-end [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W	[3]	30			30					31
Economic loss development after recoveries for R&W	[4]	(2)		1	(1)		3
Financial Guaranty Variable Interest Entities and Other [Member] | RMBS [Member] | Second Lien [Member] | HELOCs [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W	[3]	6			6					7
Economic loss development after recoveries for R&W	[4]	2		1	0		59
Financial Guaranty Variable Interest Entities and Other [Member] | Triple-X Life Insurance Transaction [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W	[3]	0			0					0
Economic loss development after recoveries for R&W	[4]	0		0	0		0
Financial Guaranty Variable Interest Entities and Other [Member] | Trust Preferred Securities (TruPS) [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W	[3]	0			0					0
Economic loss development after recoveries for R&W	[4]	0		0	0		0
Financial Guaranty Variable Interest Entities and Other [Member] | Student Loan [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W	[3]	0			0					0
Economic loss development after recoveries for R&W	[4]	0		0	0		0
Financial Guaranty Variable Interest Entities and Other [Member] | Other structured finance [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W	[3]	19			19					(4)
Economic loss development after recoveries for R&W	[4]	1		0	0		(1)
Financial Guaranty Variable Interest Entities and Other [Member] | Structured Finance [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W	[3]	133			133					122
Economic loss development after recoveries for R&W	[4]	(1)		7	1		53
Financial Guarantee Accounted for as Credit Derivatives [Member] | Subtotal [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W	[5]	113			113					58
Economic loss development after recoveries for R&W	[2]	(14)		(20)	(31)		(31)
Financial Guarantee Accounted for as Credit Derivatives [Member] | Public Finance [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W	[5]	0			0					0
Economic loss development after recoveries for R&W	[2]	(6)		(1)	(6)		(1)
Financial Guarantee Accounted for as Credit Derivatives [Member] | Public Finance [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W	[5]	0			0					0
Economic loss development after recoveries for R&W	[2]	(6)		0	(6)		0
Financial Guarantee Accounted for as Credit Derivatives [Member] | Public Finance [Member] | Non United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W	[5]	0			0					0
Economic loss development after recoveries for R&W	[2]	0		(1)	0		(1)
Financial Guarantee Accounted for as Credit Derivatives [Member] | RMBS [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W	[5]	53			53					73
Economic loss development after recoveries for R&W	[2]	(6)		(20)	(13)		(15)
Financial Guarantee Accounted for as Credit Derivatives [Member] | RMBS [Member] | First Lien [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W	[5]	49			49					69
Economic loss development after recoveries for R&W	[2]	(7)		(15)	(13)		(14)
Financial Guarantee Accounted for as Credit Derivatives [Member] | RMBS [Member] | First Lien [Member] | Prime [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W	[5]	(1)			(1)					2
Economic loss development after recoveries for R&W	[2]	0		(8)	(1)		(11)
Financial Guarantee Accounted for as Credit Derivatives [Member] | RMBS [Member] | First Lien [Member] | Alt-A [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W	[5]	(12)			(12)					(1)
Economic loss development after recoveries for R&W	[2]	(3)		(5)	(10)		(4)
Financial Guarantee Accounted for as Credit Derivatives [Member] | RMBS [Member] | First Lien [Member] | Option ARM [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W	[5]	2			2					(1)
Economic loss development after recoveries for R&W	[2]	1		(1)	4		(1)
Financial Guarantee Accounted for as Credit Derivatives [Member] | RMBS [Member] | First Lien [Member] | Subprime [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W	[5]	60			60					69
Economic loss development after recoveries for R&W	[2]	(5)		(1)	(6)		2
Financial Guarantee Accounted for as Credit Derivatives [Member] | RMBS [Member] | Second Lien [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W	[5]	4			4					4
Economic loss development after recoveries for R&W	[2]	1		(5)	0		(1)
Financial Guarantee Accounted for as Credit Derivatives [Member] | RMBS [Member] | Second Lien [Member] | Closed-end [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W	[5]	4			4					4
Economic loss development after recoveries for R&W	[2]	1		(5)	0		(1)
Financial Guarantee Accounted for as Credit Derivatives [Member] | RMBS [Member] | Second Lien [Member] | HELOCs [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W	[5]	0			0					0
Economic loss development after recoveries for R&W	[2]	0		0	0		0
Financial Guarantee Accounted for as Credit Derivatives [Member] | Triple-X Life Insurance Transaction [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W	[5]	8			8					8
Economic loss development after recoveries for R&W	[2]	1		1	2		1
Financial Guarantee Accounted for as Credit Derivatives [Member] | Trust Preferred Securities (TruPS) [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W	[5]	10			10					22
Economic loss development after recoveries for R&W	[2]	(4)		0	(12)		(18)
Financial Guarantee Accounted for as Credit Derivatives [Member] | Student Loan [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W	[5]	0			0					0
Economic loss development after recoveries for R&W	[2]	0		0	0		0
Financial Guarantee Accounted for as Credit Derivatives [Member] | Other structured finance [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W	[5]	42			42					(45)
Economic loss development after recoveries for R&W	[2]	1		0	(2)		2
Financial Guarantee Accounted for as Credit Derivatives [Member] | Structured Finance [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W	[5]	113			113					$ 58
Economic loss development after recoveries for R&W	[2]	$ (8)		$ (19)	$ (25)		$ (30)

[1] Includes expected LAE to be paid of $15 million as of June 30, 2015 and $16 million as of December 31, 2014.

[2] Refer to Note 9, Financial Guaranty Contracts Accounted for as Credit Derivatives.

[3] Refer to Note 10, Consolidated Variable Interest Entities.

[4] Refer to Note 10, Consolidated Variable Interest Entities.

[5] Refer to Note 9, Financial Guaranty Contracts Accounted for as Credit Derivatives.