Financial Guaranty Contracts Accounted for as Credit Derivatives (Details 2) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Distribution of Credit Derivative Net Par Outstanding
Net Par Outstanding	$ 59,109	$ 70,781
Percentage of total	100.00%	100.00%
AAA
Distribution of Credit Derivative Net Par Outstanding
Net Par Outstanding	41,753	50,918
Percentage of total	70.60%	71.90%
AA
Distribution of Credit Derivative Net Par Outstanding
Net Par Outstanding	3,660	3,083
Percentage of total	6.20%	4.40%
A
Distribution of Credit Derivative Net Par Outstanding
Net Par Outstanding	3,592	5,487
Percentage of total	6.10%	7.80%
BBB
Distribution of Credit Derivative Net Par Outstanding
Net Par Outstanding	5,125	4,584
Percentage of total	8.70%	6.40%
Below investment grade (BIG)
Distribution of Credit Derivative Net Par Outstanding
Net Par Outstanding	$ 4,979	$ 6,709
Percentage of total	8.40%	9.50%