Financial Guaranty Contracts Accounted for as Credit Derivatives - Effect of Changes in Credit Spread (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015		Dec. 31, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Credit Risk Derivatives, 100 Percent Widening in Spreads, Effect on Fair Value	[1]	$ (742)
Credit Risk Derivatives, 50 Percent Widening in Spreads, Effect on Fair Value	[1]	(554)
Credit Risk Derivatives, 25 Percent Widening in Spreads, Effect on Fair Value	[1]	(460)
Credit Risk Derivatives, 10 Percent Widening in Spreads, Effect on Fair Value	[1]	(403)
Fair Value of Credit Derivative Asset (Liability), net	[2]	(365)	[1]	$ (895)
Credit Risk Derivatives, 10 Percent Narrowing in Spreads, Effect on Fair Value	[1]	(330)
Credit Risk Derivatives, 25 Percent Narrowing in Spreads, Effect on Fair Value	[1]	(277)
Credit Risk Derivatives, 50 Percent Narrowing in Spreads, Effect on Fair Value	[1]	(190)
Credit Risk Derivatives, 100 Percent Widening in Spreads, Effect on Unrealized Gain (Loss)	[1]	(377)
Credit Risk Derivatives, 50 Percent Widening in Spreads, Effect on Unrealized Gain (Loss)	[1]	(189)
Credit Risk Derivatives, 25 Percent Widening in Spreads, Effect on Unrealized Gain (Loss)	[1]	(95)
Credit Risk Derivatives, 10 Percent Widening in Spreads, Effect on Unrealized Gain (Loss)	[1]	(38)
Credit Risk Derivatives, Base Scenario, Effect on Unrealized Gain (Loss)	[1]	0
Credit Risk Derivatives, 10 Percent Narrowing in Spreads, Effect on Unrealized Gain (Loss)	[1]	35
Credit Risk Derivatives, 25 Percent Narrowing in Spreads, Effect on Unrealized Gain (Loss)	[1]	88
Credit Risk Derivatives, 50 Percent Narrowing in Spreads, Effect on Unrealized Gain (Loss)	[1]	$ 175

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

[2] December 31, 2015 amount includes $44 million of net fair value loss of credit derivatives acquired from Radian Asset.