Financial Guaranty Contracts Accounted for as Credit Derivatives - Net Fair Value and Expected Losses of Credit Derivatives by Sector (Details) - USD ($) $ in Millions		Sep. 30, 2015		Dec. 31, 2014
Credit Derivatives
Net fair value of credit derivatives	[2]	$ (847)	[1]	$ (895)
Expected Loss to be (Paid) Recovered	[3]	(27)		(58)
Pooled corporate obligations [Member]
Credit Derivatives
Net fair value of credit derivatives		(231)		(49)
Expected Loss to be (Paid) Recovered	[3]	(67)		(23)
RMBS [Member] | United States [Member]
Credit Derivatives
Net fair value of credit derivatives		(346)		(494)
Expected Loss to be (Paid) Recovered	[3]	19		(73)
CMBS [Member]
Credit Derivatives
Net fair value of credit derivatives		(40)		0
Expected Loss to be (Paid) Recovered	[3]	(7)		0
Other [Member]
Credit Derivatives
Net fair value of credit derivatives		(230)		(352)
Expected Loss to be (Paid) Recovered	[3]	28		38
Credit Risk Contract [Member]
Credit Derivatives
R&W Included in Credit Derivative Asset (Liability)		$ 82		$ 86

[1] Includes the effects of spreads on both the underlying asset classes and the Company’s own credit spread.

[2] September 30, 2015 amount includes $174 million of net fair value loss of credit derivatives acquired from Radian Asset.

[3] Includes R&W benefit of $82 million as of September 30, 2015 and $86 million as of December 31, 2014.