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
		Mar. 31, 2016		Mar. 31, 2015	Dec. 31, 2015		Jun. 30, 2015	Dec. 31, 2014
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		$ 1,337	[1]	$ 1,154	$ 1,391	[1]		$ 1,169
Economic loss development after recoveries for R&W		59		(3)
Subtotal [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		1,337			1,391
Economic loss development after recoveries for R&W		59		(3)
Public Finance [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		903	[1]	352	809	[1]		348
Economic loss development after recoveries for R&W		99		6
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		864	[1]	310	771	[1]	$ 771	303
Economic loss development after recoveries for R&W		98		9
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		39	[1]	42	38	[1]		45
Economic loss development after recoveries for R&W		1		(3)
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		293	[1]	570	409	[1]		584
Economic loss development after recoveries for R&W		(31)		4
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		228	[1]	569	348	[1]		595
Economic loss development after recoveries for R&W		(36)		(2)
RMBS [Member] | First Lien [Member] | Financing Receivable, 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]	3	(2)	[1]		4
Economic loss development after recoveries for R&W		0		0
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		36	[1]	289	127	[1]		304
Economic loss development after recoveries for R&W		(16)		(5)
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		(47)	[1]	(16)	(28)	[1]		(16)
Economic loss development after recoveries for R&W		(21)		4
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		240	[1]	293	251	[1]		303
Economic loss development after recoveries for R&W		1		(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		65	[1]	1	61	[1]		(11)
Economic loss development after recoveries for R&W		5		6
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		102	[1]	165	99	[1]		161
Economic loss development after recoveries for R&W		4		5
Student Loan [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		32	[1]	62	54	[1]		68
Economic loss development after recoveries for R&W		(14)		(6)
Other structured finance [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		7	[1]	5	20	[1]		8
Economic loss development after recoveries for R&W		1		(12)
Structured Finance [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net expected loss to be paid after recoveries for R&W		434	[1]	802	582	[1]		$ 821
Economic loss development after recoveries for R&W		(40)		(9)
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		1,210			1,239
Economic loss development after recoveries for R&W		61		12
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		903			809
Economic loss development after recoveries for R&W		99		6
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		864			771
Economic loss development after recoveries for R&W		98		9
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		39			38
Economic loss development after recoveries for R&W		1		(3)
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		144			251
Economic loss development after recoveries for R&W		(31)		8
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		125			238
Economic loss development after recoveries for R&W		(33)		0
Financial Guarantee Accounted for as Insurance Contracts [Member] | RMBS [Member] | First Lien [Member] | Financing Receivable, 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
Economic loss development after recoveries for R&W		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		19			110
Economic loss development after recoveries for R&W		(17)		2
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		(44)			(27)
Economic loss development after recoveries for R&W		(19)		1
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		148			153
Economic loss development after recoveries for R&W		3		(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		19			13
Economic loss development after recoveries for R&W		2		8
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		91			88
Economic loss development after recoveries for R&W		3		4
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		32			54
Economic loss development after recoveries for R&W		(14)		(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		40			37
Economic loss development after recoveries for R&W		4		0
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		307			430
Economic loss development after recoveries for R&W		(38)		6
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	[2]	118			136
Economic loss development after recoveries for R&W	[3]	4		2
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	[2]	0			0
Economic loss development after recoveries for R&W	[3]	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	[2]	0			0
Economic loss development after recoveries for R&W	[3]	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	[2]	0			0
Economic loss development after recoveries for R&W	[3]	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	[2]	116			120
Economic loss development after recoveries for R&W	[3]	4		3
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	[2]	73			76
Economic loss development after recoveries for R&W	[3]	1		4
Financial Guaranty Variable Interest Entities and Other [Member] | RMBS [Member] | First Lien [Member] | Financing Receivable, 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]	0			0
Economic loss development after recoveries for R&W	[3]	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	[2]	18			17
Economic loss development after recoveries for R&W	[3]	1		0
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	[2]	0			0
Economic loss development after recoveries for R&W	[3]	0		0
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	[2]	55			59
Economic loss development after recoveries for R&W	[3]	0		4
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	[2]	43			44
Economic loss development after recoveries for R&W	[3]	3		(1)
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	[2]	0			0
Economic loss development after recoveries for R&W	[3]	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	[2]	0			0
Economic loss development after recoveries for R&W	[3]	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	[2]	2			16
Economic loss development after recoveries for R&W	[3]	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	[2]	118			136
Economic loss development after recoveries for R&W	[3]	4		2
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	[4]	9			16
Economic loss development after recoveries for R&W	[5]	(6)		(17)
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	[4]	0			0
Economic loss development after recoveries for R&W	[5]	0		0
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	[4]	0			0
Economic loss development after recoveries for R&W	[5]	0		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	[4]	0			0
Economic loss development after recoveries for R&W	[5]	0		0
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	[4]	33			38
Economic loss development after recoveries for R&W	[5]	(4)		(7)
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	[4]	30			34
Economic loss development after recoveries for R&W	[5]	(4)		(6)
Financial Guarantee Accounted for as Credit Derivatives [Member] | RMBS [Member] | First Lien [Member] | Financing Receivable, 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	[4]	(3)			(4)
Economic loss development after recoveries for R&W	[5]	0		(1)
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	[4]	(1)			0
Economic loss development after recoveries for R&W	[5]	0		(7)
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	[4]	(3)			(1)
Economic loss development after recoveries for R&W	[5]	(2)		3
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	[4]	37			39
Economic loss development after recoveries for R&W	[5]	(2)		(1)
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	[4]	3			4
Economic loss development after recoveries for R&W	[5]	0		(1)
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	[4]	11			11
Economic loss development after recoveries for R&W	[5]	1		1
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	[4]	0			0
Economic loss development after recoveries for R&W	[5]	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	[4]	(35)			(33)
Economic loss development after recoveries for R&W	[5]	(3)		(11)
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	[4]	9			$ 16
Economic loss development after recoveries for R&W	[5]	$ (6)		$ (17)

[1] Includes expected LAE to be paid of $9 million as of March 31, 2016 and $12 million as of December 31, 2015.

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

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

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

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