Long-Term Debt and Credit Facilities - Credit Facilities (Details) (USD $)	0 Months Ended
	Feb. 07, 2014 2009 Strip Coverage Facility AGM	Mar. 31, 2014 2009 Strip Coverage Facility AGM	Jul. 01, 2009 2009 Strip Coverage Facility AGM	Jun. 30, 2009 2009 Strip Coverage Facility AGM	Oct. 25, 2013 AGUS Revolving Credit Facility
Credit facilities
Liquidity claims on gross exposure		$ 1,400,000,000
Cumulative strip par exposure terminated		1,400,000,000
Maximum credit facility	500,000,000		1,000,000,000		225,000,000
Line of Credit Facility, Increase (Decrease) in Maximum Borrowing Capacity	(460,000,000)
Fixed interest rate as percentage of federal rate					100.00%
Reduced commitment amount to trigger termination		499,000,000
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%