Outstanding Exposure - Net Direct Economic Exposure to Selected European Countries (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	$ 2,863	[1]
Hungary
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	587	[1],[2]
Ireland
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	145	[1]
Italy
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	1,591	[1]
Portugal
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	110	[1],[2]
Spain
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	430	[1],[2]
Sovereign and sub-sovereign exposure
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	1,954	[1]
Sovereign and sub-sovereign exposure | Non-infrastructure public finance
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	1,398	[1],[3]
Sovereign and sub-sovereign exposure | Infrastructure finance
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	556	[1]
Sovereign and sub-sovereign exposure | Hungary
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	370	[1],[2]
Sovereign and sub-sovereign exposure | Hungary | Non-infrastructure public finance
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	0	[1],[2],[3]
Sovereign and sub-sovereign exposure | Hungary | Infrastructure finance
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	370	[1],[2]
Sovereign and sub-sovereign exposure | Ireland
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	0	[1]
Sovereign and sub-sovereign exposure | Ireland | Non-infrastructure public finance
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	0	[1],[3]
Sovereign and sub-sovereign exposure | Ireland | Infrastructure finance
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	0	[1]
Sovereign and sub-sovereign exposure | Italy
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	1,044	[1]
Sovereign and sub-sovereign exposure | Italy | Non-infrastructure public finance
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	1,026	[1],[3]
Sovereign and sub-sovereign exposure | Italy | Infrastructure finance
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	18	[1]
Sovereign and sub-sovereign exposure | Portugal
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	110	[1],[2]
Sovereign and sub-sovereign exposure | Portugal | Non-infrastructure public finance
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	98	[1],[2],[3]
Sovereign and sub-sovereign exposure | Portugal | Infrastructure finance
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	12	[1],[2]
Sovereign and sub-sovereign exposure | Spain
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	430	[1],[2]
Sovereign and sub-sovereign exposure | Spain | Non-infrastructure public finance
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	274	[1],[2],[3]
Sovereign and sub-sovereign exposure | Spain | Infrastructure finance
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	156	[1],[2]
Non-sovereign exposure
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	909	[1]
Non-sovereign exposure | Regulated utilities
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	235	[1]
Non-sovereign exposure | RMBS
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	674	[1]
Non-sovereign exposure | Hungary
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	217	[1],[2]
Non-sovereign exposure | Hungary | Regulated utilities
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	0	[1],[2]
Non-sovereign exposure | Hungary | RMBS
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	217	[1],[2]
Non-sovereign exposure | Ireland
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	145	[1]
Non-sovereign exposure | Ireland | Regulated utilities
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	0	[1]
Non-sovereign exposure | Ireland | RMBS
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	145	[1]
Non-sovereign exposure | Italy
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	547	[1]
Non-sovereign exposure | Italy | Regulated utilities
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	235	[1]
Non-sovereign exposure | Italy | RMBS
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	312	[1]
Non-sovereign exposure | Portugal
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	0	[1],[2]
Non-sovereign exposure | Portugal | Regulated utilities
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	0	[1],[2]
Non-sovereign exposure | Portugal | RMBS
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	0	[1],[2]
Non-sovereign exposure | Spain
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	0	[1],[2]
Non-sovereign exposure | Spain | Regulated utilities
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	0	[1],[2]
Non-sovereign exposure | Spain | RMBS
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	0	[1],[2]
Below investment grade (BIG)
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	1,126	[1]
Below investment grade (BIG) | Hungary
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	587	[1],[2]
Below investment grade (BIG) | Ireland
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	0	[1]
Below investment grade (BIG) | Italy
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	0	[1]
Below investment grade (BIG) | Portugal
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	110	[1],[2]
Below investment grade (BIG) | Spain
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	429	[1],[2]
Europe [Member] | Pooled corporate obligations
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	710
Europe [Member] | Commercial Receivable [Member]
Financial guarantee obligations
Net Economic Exposure to Selected European Countries	$ 89

[1] While the Company’s exposures are shown in U.S. dollars, the obligations the Company insures are in various currencies, including U.S. dollars and Euros. Included in the table above is $145 million of reinsurance assumed on a 2004 - 2006 pool of Irish residential mortgages that is part of the Company’s remaining legacy mortgage reinsurance business. One of the residential mortgage-backed securities included in the table above includes residential mortgages in both Italy and Germany, and only the portion of the transaction equal to the portion of the original mortgage pool in Italian mortgages is shown in the table.

[2] See Note 5, Expected Loss to be Paid.

[3] The exposure shown in the “Non-infrastructure public finance” category is from transactions backed by receivable payments from sub-sovereigns in Italy, Spain and Portugal. Sub-sovereign debt is debt issued by a governmental entity or government backed entity, or supported by such an entity, that is other than direct sovereign debt of the ultimate governing body of the country.