Financial Guaranty Contracts Accounted for as Credit Derivatives (Details 3) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Net credit derivative premiums received and receivable	$ 41,000,000	$ 34,000,000	$ 68,000,000	$ 63,000,000
Net ceding commissions (paid and payable) received and receivable	0	0	1,000,000	0
Realized gains on credit derivatives	41,000,000	34,000,000	69,000,000	63,000,000
Terminations	0	(1,000,000)	0	(1,000,000)
Net credit derivative losses (paid and payable) recovered and recoverable	(127,000,000)	(56,000,000)	(137,000,000)	(142,000,000)
Total realized gains (losses) and other settlements on credit derivatives	(86,000,000)	(23,000,000)	(68,000,000)	(80,000,000)
Net unrealized gains (losses) on credit derivatives	160,000,000	284,000,000	(450,000,000)	(350,000,000)
Net change in fair value of credit derivatives	74,000,000	261,000,000	(518,000,000)	(430,000,000)
Net par of terminated CDS transactions	2,000,000,000	600,000,000	3,000,000,000	800,000,000
Proceeds from Termination of Financial Guaranty Contracts Accounted for as Credit Derivatives	14,000,000	700,000	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