Outstanding Exposure - Surveillance Categories and Debt Service Outstanding (Details) (USD $)	3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Financial guarantee obligations
Minimum amount assumed principal amount for internal rating	$ 1,000,000
Probability of paying more claims than being reimbursed (as a percent)	50.00%
Constant discount rate (as a percent)	5.00%
Maximum period of liquidity claims (in years)	1 year
Gross Debt Service Outstanding	721,176,000,000	737,380,000,000
Net Debt Service Outstanding	676,968,000,000	690,535,000,000
Mortgage guaranty insurance	153,000,000
Public finance
Financial guarantee obligations
Gross Debt Service Outstanding	639,981,000,000	650,924,000,000
Net Debt Service Outstanding	601,433,000,000	610,011,000,000
Structured finance
Financial guarantee obligations
Gross Debt Service Outstanding	81,195,000,000	86,456,000,000
Net Debt Service Outstanding	75,535,000,000	80,524,000,000
Public finance Ireland
Financial guarantee obligations
Mortgage guaranty insurance	145,000,000
Public finance UK
Financial guarantee obligations
Mortgage guaranty insurance	$ 8,000,000