label1truetruefalse0.40.4falsefalsefalsefalsefalse2falsetruefalse00falsefalsefalsefalsefalseOtherus-types:percentItemTypepurePeak-To-Trough Housing Price Decline MaximumNo authoritative reference available.falsefalsePeak-to-trough housing price decline maximum10false0natruenanaNo definition available.falsetruefalsefalsefalsefalse<
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12/31/2010
As_Of_12_31_201010http://www.sec.gov/CIK0000093751instant2010-12-31T00:00:000001-01-01T00:00:00falsefalseAlt-A [Member]invest_InvestmentAxisxbrldihttp://xbrl.org/2006/xbrldistt_AltMemberinvest_InvestmentAxisexplicitMemberUnit13Standardhttp://www.xbrl.org/2003/instancepurexbrli04falsefalsetruefalse{invest_InvestmentAxis} : Alt-A [Member]
12/31/2009
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12/31/2010
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12/31/2009
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ne MaximumNo authoritative reference available.falsefalsePeak-to-trough housing price decline maximum1

Loss severity rates consider the initial loan-to-value ratio, lien position, geography, expected collateral value and other factors. 2

Management's expectation of the Case-Shiller National Home Price Index. 225Investment Securities (Critical Estimates Used in Roll Rate Analysis) (Details)UnKnownUnKnownUnKnownUnKnowntruetrue