Financial Guaranty Contracts Accounted for as Credit Derivatives - Distribution of Credit Derivative Net Par Outstanding by Internal Rating (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Distribution of Credit Derivative Net Par Outstanding
Net Par Outstanding	$ 51,318	$ 54,482
Percentage of total	100.00%	100.00%
AAA
Distribution of Credit Derivative Net Par Outstanding
Net Par Outstanding	35,157	38,244
Percentage of total	68.50%	70.20%
AA
Distribution of Credit Derivative Net Par Outstanding
Net Par Outstanding	3,660	3,648
Percentage of total	7.10%	6.70%
A
Distribution of Credit Derivative Net Par Outstanding
Net Par Outstanding	3,621	3,636
Percentage of total	7.10%	6.70%
BBB
Distribution of Credit Derivative Net Par Outstanding
Net Par Outstanding	4,304	4,161
Percentage of total	8.40%	7.60%
Below investment grade (BIG)
Distribution of Credit Derivative Net Par Outstanding
Net Par Outstanding	$ 4,576	$ 4,793
Percentage of total	8.90%	8.80%