Outstanding Exposure (Details 1) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Financial guarantee obligations
Gross Debt Service Outstanding	$ 757,578	$ 833,098
Net Debt Service Outstanding	709,643	780,356
Mortgage Guaranty Insured Obligations Outstanding Principal Amount	150
Public finance
Financial guarantee obligations
Gross Debt Service Outstanding	665,855	722,478
Net Debt Service Outstanding	624,425	677,285
Structured finance
Financial guarantee obligations
Gross Debt Service Outstanding	91,723	110,620
Net Debt Service Outstanding	85,218	103,071
Public finance Ireland
Financial guarantee obligations
Mortgage Guaranty Insured Obligations Outstanding Principal Amount	142
Public finance UK
Financial guarantee obligations
Mortgage Guaranty Insured Obligations Outstanding Principal Amount	8
Below investment grade (BIG)
Financial guarantee obligations
Refinement of Approach to Debt Service Outstanding, Net	$ 1,211