Outstanding Exposure - Financial Guaranty Portfolio by Internal Rating and Net Exposure to Puerto Rico (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012
Financial guarantee obligations
Net Par Outstanding (excluding loss mitigation bonds)	$ 459,107	[1]	$ 518,772	[1]
% of Net Par Outstanding	100.00%	[1]	100.00%	[1]
Net Par Outstanding (including loss mitigation bonds)	460,302	[1]	519,893	[1]
PUERTO RICO
Financial guarantee obligations
Net Par Outstanding (excluding loss mitigation bonds)	5,400
Public Finance U.S.
Financial guarantee obligations
Net Par Outstanding (excluding loss mitigation bonds)	352,181	[1]	387,929	[1]
% of Net Par Outstanding	100.00%	[1]	100.00%	[1]
Net Par Outstanding (including loss mitigation bonds)	352,213	[1]	387,967	[1]
Public Finance Non-U.S.
Financial guarantee obligations
Net Par Outstanding (excluding loss mitigation bonds)	33,998	[1]	37,540	[1]
% of Net Par Outstanding	100.00%	[1]	100.00%	[1]
Net Par Outstanding (including loss mitigation bonds)	33,998	[1]	37,540	[1]
Structured Finance U.S.
Financial guarantee obligations
Net Par Outstanding (excluding loss mitigation bonds)	58,907	[1]	74,535	[1]
% of Net Par Outstanding	100.00%	[1]	100.00%	[1]
Net Par Outstanding (including loss mitigation bonds)	60,070	[1]	75,618	[1]
Structured Finance Non-U.S.
Financial guarantee obligations
Net Par Outstanding (excluding loss mitigation bonds)	14,021	[1]	18,768	[1]
% of Net Par Outstanding	100.00%	[1]	100.00%	[1]
Net Par Outstanding (including loss mitigation bonds)	14,021	[1]	18,768	[1]
AAA
Financial guarantee obligations
Net Par Outstanding (excluding loss mitigation bonds)	48,015	[1]	61,564	[1]
% of Net Par Outstanding	10.50%	[1]	11.90%	[1]
AAA | Public Finance U.S.
Financial guarantee obligations
Net Par Outstanding (excluding loss mitigation bonds)	4,998	[1]	4,502	[1]
% of Net Par Outstanding	1.40%	[1]	1.20%	[1]
AAA | Public Finance Non-U.S.
Financial guarantee obligations
Net Par Outstanding (excluding loss mitigation bonds)	1,016	[1]	1,706	[1]
% of Net Par Outstanding	3.00%	[1]	4.50%	[1]
AAA | Structured Finance U.S.
Financial guarantee obligations
Net Par Outstanding (excluding loss mitigation bonds)	32,317	[1]	42,187	[1]
% of Net Par Outstanding	54.90%	[1]	56.60%	[1]
AAA | Structured Finance Non-U.S.
Financial guarantee obligations
Net Par Outstanding (excluding loss mitigation bonds)	9,684	[1]	13,169	[1]
% of Net Par Outstanding	69.10%	[1]	70.20%	[1]
AA
Financial guarantee obligations
Net Par Outstanding (excluding loss mitigation bonds)	117,933	[1]	135,665	[1]
% of Net Par Outstanding	25.70%	[1]	26.10%	[1]
AA | Public Finance U.S.
Financial guarantee obligations
Net Par Outstanding (excluding loss mitigation bonds)	107,503	[1]	124,525	[1]
% of Net Par Outstanding	30.50%	[1]	32.10%	[1]
AA | Public Finance Non-U.S.
Financial guarantee obligations
Net Par Outstanding (excluding loss mitigation bonds)	422	[1]	875	[1]
% of Net Par Outstanding	1.20%	[1]	2.30%	[1]
AA | Structured Finance U.S.
Financial guarantee obligations
Net Par Outstanding (excluding loss mitigation bonds)	9,431	[1]	9,543	[1]
% of Net Par Outstanding	16.00%	[1]	12.80%	[1]
AA | Structured Finance Non-U.S.
Financial guarantee obligations
Net Par Outstanding (excluding loss mitigation bonds)	577	[1]	722	[1]
% of Net Par Outstanding	4.10%	[1]	3.90%	[1]
A
Financial guarantee obligations
Net Par Outstanding (excluding loss mitigation bonds)	205,616	[1]	225,984	[1]
% of Net Par Outstanding	44.80%	[1]	43.60%	[1]
A | Public Finance U.S.
Financial guarantee obligations
Net Par Outstanding (excluding loss mitigation bonds)	192,841	[1]	210,124	[1]
% of Net Par Outstanding	54.80%	[1]	54.10%	[1]
A | Public Finance Non-U.S.
Financial guarantee obligations
Net Par Outstanding (excluding loss mitigation bonds)	9,453	[1]	9,781	[1]
% of Net Par Outstanding	27.90%	[1]	26.10%	[1]
A | Structured Finance U.S.
Financial guarantee obligations
Net Par Outstanding (excluding loss mitigation bonds)	2,580	[1]	4,670	[1]
% of Net Par Outstanding	4.40%	[1]	6.30%	[1]
A | Structured Finance Non-U.S.
Financial guarantee obligations
Net Par Outstanding (excluding loss mitigation bonds)	742	[1]	1,409	[1]
% of Net Par Outstanding	5.30%	[1]	7.50%	[1]
BBB
Financial guarantee obligations
Net Par Outstanding (excluding loss mitigation bonds)	65,005	[1]	73,262	[1]
% of Net Par Outstanding	14.10%	[1]	14.10%	[1]
BBB | Public Finance U.S.
Financial guarantee obligations
Net Par Outstanding (excluding loss mitigation bonds)	37,745	[1]	44,213	[1]
% of Net Par Outstanding	10.70%	[1]	11.40%	[1]
BBB | Public Finance Non-U.S.
Financial guarantee obligations
Net Par Outstanding (excluding loss mitigation bonds)	21,499	[1]	22,885	[1]
% of Net Par Outstanding	63.20%	[1]	61.00%	[1]
BBB | Structured Finance U.S.
Financial guarantee obligations
Net Par Outstanding (excluding loss mitigation bonds)	3,815	[1]	3,737	[1]
% of Net Par Outstanding	6.40%	[1]	5.00%	[1]
BBB | Structured Finance Non-U.S.
Financial guarantee obligations
Net Par Outstanding (excluding loss mitigation bonds)	1,946	[1]	2,427	[1]
% of Net Par Outstanding	13.90%	[1]	12.90%	[1]
BIG
Financial guarantee obligations
Net Par Outstanding (excluding loss mitigation bonds)	22,538	[1]	22,297	[1]
% of Net Par Outstanding	4.90%	[1]	4.30%	[1]
BIG | PUERTO RICO
Financial guarantee obligations
Net Par Outstanding (excluding loss mitigation bonds)	5,171
BIG | Loss Mitigation Bonds
Financial guarantee obligations
Net Par Outstanding (including loss mitigation bonds)	1,195	[1]	1,121	[1]
BIG | PUERTO RICO | PUERTO RICO
Financial guarantee obligations
Net Par Outstanding (excluding loss mitigation bonds)	5,200
BIG | Public Finance U.S.
Financial guarantee obligations
Net Par Outstanding (excluding loss mitigation bonds)	9,094	[1]	4,565	[1]
% of Net Par Outstanding	2.60%	[1]	1.20%	[1]
BIG | Public Finance U.S. | Loss Mitigation Bonds
Financial guarantee obligations
Net Par Outstanding (including loss mitigation bonds)	32	[1]	38	[1]
BIG | Public Finance Non-U.S.
Financial guarantee obligations
Net Par Outstanding (excluding loss mitigation bonds)	1,608	[1]	2,293	[1]
% of Net Par Outstanding	4.70%	[1]	6.10%	[1]
BIG | Public Finance Non-U.S. | Loss Mitigation Bonds
Financial guarantee obligations
Net Par Outstanding (including loss mitigation bonds)	0	[1]	0	[1]
BIG | Structured Finance U.S.
Financial guarantee obligations
Net Par Outstanding (excluding loss mitigation bonds)	10,764	[1]	14,398	[1]
% of Net Par Outstanding	18.30%	[1]	19.30%	[1]
BIG | Structured Finance U.S. | Loss Mitigation Bonds
Financial guarantee obligations
Net Par Outstanding (including loss mitigation bonds)	1,163	[1]	1,083	[1]
BIG | Structured Finance Non-U.S.
Financial guarantee obligations
Net Par Outstanding (excluding loss mitigation bonds)	1,072	[1]	1,041	[1]
% of Net Par Outstanding	7.60%	[1]	5.50%	[1]
BIG | Structured Finance Non-U.S. | Loss Mitigation Bonds
Financial guarantee obligations
Net Par Outstanding (including loss mitigation bonds)	$ 0	[1]	$ 0	[1]

[1] In the third quarter of 2013, the Company adjusted its approach to assigning internal ratings. See "Refinement of Approach to Internal Credit Ratings and Surveillance Categories" above. This approach is reflected in the "Financial Guaranty Portfolio by Internal Rating" tables as of both December 31, 2013 and December 31, 2012.