Long-Term Debt and Credit Facilities (Details 2) (USD $)				3 Months Ended
	Mar. 31, 2012	Mar. 31, 2012 2009 Strip Coverage Facility AGM Transaction	Jul. 01, 2009 2009 Strip Coverage Facility AGM	Mar. 31, 2012 AG Re Credit Facility	Mar. 31, 2012 Letter of credit agreement with Bank of New York Mellon AGC	Mar. 31, 2012 Letter of credit agreement with Royal Bank of Scotland AGC
Credit facilities
Number of leveraged lease transactions due to 2008 downgrade		45
Liquidity claims on gross exposure		$ 1,000,000,000
Number of leveraged lease transactions due to 2011 downgrade		26
Liquidity claims on additional gross exposure		991,000,000
Cumulative strip par exposure terminated		607,000,000
Maximum credit facility			1,000,000,000	200,000,000	2,900,000	2,900,000
Reduced commitment amount to trigger termination		979,800,000
Reduced maximum credit facility for 2014 if consolidated net worth not maintained		750,000,000
Amount to be added to net worth requirement if borrowing capacity is reduced		0
Maximum debt-to-capital ratio which is required to be maintained (as a percent)		30.00%
Minimum net worth which is required to be maintained (as a percent)			75.00%
Minimum percentage of aggregate consolidate net income (or loss) for July 1, 2009 through June 30, 2014 to be added to net worth requirement		25.00%
Threshold cumulative municipal losses to utilize credit facility				260,000,000
Threshold cumulative municipal losses as a percent of debt service to utilize credit facility				4.50%
Amount outstanding under letter of credit	$ 2,900,000