Financial Guaranty Contracts Accounted for as Credit Derivatives (Details 3) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Net credit derivative premiums received and receivable	$ 24,000,000	$ 33,000,000	$ 92,000,000	$ 96,000,000
Net ceding commissions (paid and payable) received and receivable	0	0	1,000,000	0
Realized gains on credit derivatives	24,000,000	33,000,000	93,000,000	96,000,000
Terminations	0	0	0	(1,000,000)
Net credit derivative losses (paid and payable) recovered and recoverable	0	(31,000,000)	(137,000,000)	(173,000,000)
Total realized gains (losses) and other settlements on credit derivatives	24,000,000	2,000,000	(44,000,000)	(78,000,000)
Net unrealized gains (losses) on credit derivatives	330,000,000	(38,000,000)	(120,000,000)	(388,000,000)
Net change in fair value of credit derivatives	354,000,000	(36,000,000)	(164,000,000)	(466,000,000)
Net par of terminated CDS transactions	300,000,000	300,000,000	3,300,000,000	1,100,000,000
Proceeds from Termination of Financial Guaranty Contracts Accounted for as Credit Derivatives	0	400,000	15,000,000	1,000,000
Film securitization [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Net unrealized gains (losses) on credit derivatives	(127,000,000)
Net change in fair value of credit derivatives	(7,000,000)
Payments from Termination of Financial Guaranty Contracts Accounted for as Credit Derivatives	$ 120,000,000