Income Taxes (Narrative) (Details) (USD $)	9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2010
Variable Interest Entity [Line Items]
Federal statutory rate	35.00%
Capital loss carryforwards			$ 413,000,000
NOL carryforwards	782,000,000
Minimum tax credit carryforward	46,000,000
Deferred tax assets related to losses on insured credit derivatives	1,600,000,000
Insured credit derivatives	4,500,000,000
Unrealizable deferred tax assets	1,300,000,000
Decrease in cumulative ownership change	28.60%
Cumulative ownership shift	50.00%
Percentage of ownership of new owners	5.00%
Taxable income projection, years	15Y
Maximum taxable income projection years	20Y
Deferred tax assets related to unrealized losses on investments	76,000,000
Defined testing period for ownership change, approximate years	3Y
Cumulative undistributed earnings	38,000,000	122,000,000
Non Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Deferred income taxes, net	1,298,000,000		908,000,000
Valuation allowance	342,000,000		376,000,000
Valuation allowance decrease	$ 34,000,000