Represents the outstanding principal amounts of the underlying insured obligations for financial guaranty contracts accounted for as insurance, net of ceded contracts.

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Represents the outstanding principal amounts of the underlying insured obligations for financial guaranty contracts accounted for as insurance.

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Represents the net basis of the underlying insured obligations for financial guaranty contracts accounted for as insurance.

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Represents the percentage of reduction on the principal amounts of the underlying insured obligations for financial guaranty contracts accounted for as insurance.

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Represents the stated percentage paid in surplus notes issued by the segregated account.

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Represents the stated percentage paid in cash of permitted claims under the policies in the segarated account.

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Liability as of the balance sheet date for amounts representing estimated cost of settling unpaid claims under the terms of the underlying insurance policies, less estimated reinsurance recoveries on such claims, for the largest loss on a single insured transaction.

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Represents the maximum period of covenants to deliver GAAP-compliant quarterly financial statements for the entity and its consolidated subsidiaries within each quarter.

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Represents the maximum period of covenants to deliver GAAP-compliant quarterly financial statements for the entity and its consolidated subsidiaries at the end of the fiscal year.

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The value (monetary amount) of the award the plaintiff seeks in the legal matter.

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Reflects the estimated amount of loss from the specified contingency as of the balance sheet date.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Subsequent Events (Details) In Millions, unless otherwise specified	6 Months Ended	1 Months Ended			6 Months Ended			6 Months Ended											1 Months Ended		6 Months Ended
	Jun. 30, 2011 Debt relief	Sep. 30, 2010 AGM Litigation New York Legal Proceedings USD ($)	Sep. 29, 2010 AGM Litigation New York Legal Proceedings USD ($)	Apr. 08, 2011 AG Re and AGC Litigation New York Legal Proceedings	Jun. 30, 2011 Sovereign debt of Greece with a 4.5% fixed coupon	Sep. 30, 2011 Sovereign debt of Greece with a 4.5% fixed coupon USD ($)	Sep. 30, 2011 Sovereign debt of Greece with a 4.5% fixed coupon EUR (€)	Jun. 30, 2011 Sovereign debt of Greece due in 2057 with a 2.085% inflation-linked coupon	Sep. 30, 2011 Sovereign debt of Greece due in 2057 with a 2.085% inflation-linked coupon USD ($)	Sep. 30, 2011 Sovereign debt of Greece due in 2057 with a 2.085% inflation-linked coupon EUR (€)	Jun. 30, 2011 Jefferson County Alabama Sewer Authority USD ($)	Sep. 30, 2011 Jefferson County Alabama Sewer Authority Warrants USD ($)	Jun. 30, 2011 Jefferson County Alabama Sewer Authority Warrants USD ($)	Jun. 30, 2011 Jefferson County Alabama Sewer Authority Warrants AGM USD ($)	Jun. 30, 2011 Jefferson County Alabama Sewer Authority Warrants AG Re and AGRO USD ($)	Jun. 30, 2011 Jefferson County Alabama Sewer Authority Bonds USD ($)	Jun. 30, 2011 Jefferson County Alabama Sewer Authority Bonds AGM USD ($)	Jun. 30, 2011 Jefferson County Alabama Sewer Authority Bonds AG Re and AGRO USD ($)	Mar. 31, 2011 AGM Litigation New York USD ($)	Mar. 29, 2011 AGM Litigation New York USD ($)	Jun. 30, 2011 AGM 2006 Credit Facility D
Subsequent Event
Exposure through financial guarantees of debt, gross							€ 200.0			€ 1,135.0
Exposure through financial guarantees of debt, net						165.1			52.4
Coupon rate (as a percent)					4.50%			2.085%
Reduction of the notional amount due to relief measures related to sovereign debt of Greece (as a percent)	50.00%
Amount to be repaid to the MARM 2006-OA2 trust as per court order		7.2																	7.2
Estimated unreimbursed claims			144																	144
Maximum period of covenants to deliver GAAP-compliant quarterly financial statements for the entity and its consolidated subsidiaries after each quarter (in days)																					60
Maximum period of covenants to deliver GAAP-compliant quarterly financial statements for the entity and its consolidated subsidiaries after the end of the fiscal year (in days)																					115
Percentage paid in cash				25.00%
Percentage paid in surplus notes				75.00%
Net Par Outstanding Financial Guaranty Insurance											731.8		495.8	135.2	360.6	236.0	164.1	71.9
Largest expected loss to be paid for a single transaction												$ 18.0	$ 31.1			$ 1.0