Valuation (Schedule Of Significant Unobservable Inputs, Qualitative Information) (Details) (USD $) In Thousands, unless otherwise specified							9 Months Ended				9 Months Ended				9 Months Ended				9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2012 Level 3 [Member]	Dec. 31, 2011 Level 3 [Member]	Sep. 30, 2012 Level 3 [Member] Income Approach Valuation Technique [Member] Private Label Residential Mortgage Backed Securities And Securitized Debt [Member]		Sep. 30, 2012 Level 3 [Member] Income Approach Valuation Technique [Member] Private Label Residential Mortgage Backed Securities And Securitized Debt [Member] Minimum [Member]	Sep. 30, 2012 Level 3 [Member] Income Approach Valuation Technique [Member] Private Label Residential Mortgage Backed Securities And Securitized Debt [Member] Maximum [Member]	Sep. 30, 2012 Level 3 [Member] Income Approach Valuation Technique [Member] Private Label Residential Mortgage Backed Securities And Securitized Debt [Member] Weighted Average [Member]	Sep. 30, 2012 Level 3 [Member] Income Approach Valuation Technique [Member] Credit Default Swaps On Asset Backed Securities [Member]	Sep. 30, 2012 Level 3 [Member] Income Approach Valuation Technique [Member] Credit Default Swaps On Asset Backed Securities [Member] Minimum [Member]	Sep. 30, 2012 Level 3 [Member] Income Approach Valuation Technique [Member] Credit Default Swaps On Asset Backed Securities [Member] Maximum [Member]	Sep. 30, 2012 Level 3 [Member] Income Approach Valuation Technique [Member] Credit Default Swaps On Asset Backed Securities [Member] Weighted Average [Member]	Sep. 30, 2012 Level 3 [Member] Income Approach Valuation Technique [Member] Private Label Commercial Mortgage-Backed Securities And Commercial Mortgage Loans [Member]	Sep. 30, 2012 Level 3 [Member] Income Approach Valuation Technique [Member] Private Label Commercial Mortgage-Backed Securities And Commercial Mortgage Loans [Member] Minimum [Member]	Sep. 30, 2012 Level 3 [Member] Income Approach Valuation Technique [Member] Private Label Commercial Mortgage-Backed Securities And Commercial Mortgage Loans [Member] Maximum [Member]	Sep. 30, 2012 Level 3 [Member] Income Approach Valuation Technique [Member] Private Label Commercial Mortgage-Backed Securities And Commercial Mortgage Loans [Member] Weighted Average [Member]	Sep. 30, 2012 Level 3 [Member] Income Approach Valuation Technique [Member] Agency Interest Only Residential Mortgage-Backed Securities [Member]	Sep. 30, 2012 Level 3 [Member] Income Approach Valuation Technique [Member] Agency Interest Only Residential Mortgage-Backed Securities [Member] Minimum [Member]		Sep. 30, 2012 Level 3 [Member] Income Approach Valuation Technique [Member] Agency Interest Only Residential Mortgage-Backed Securities [Member] Maximum [Member]		Sep. 30, 2012 Level 3 [Member] Income Approach Valuation Technique [Member] Agency Interest Only Residential Mortgage-Backed Securities [Member] Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	$ 1,238,766	$ 1,331,104	$ 547,058	$ 504,861	$ 456,486	[1]				$ 31,460				$ 53,846				$ 3,827
Yield							2.50%	56.30%	9.40%						0.80%	13.20%	7.90%
Projected Collateral Prepayments							0.60%	47.00%	17.70%		5.60%	37.10%	15.20%						84.00%		96.20%		89.30%
Projected Collateral Losses							3.70%	87.50%	35.00%		25.00%	62.80%	43.10%		0.00%	40.10%	1.80%
Projected Collateral Recoveries							0.00%	39.50%	19.70%		10.00%	39.30%	18.90%		0.00%	23.60%	2.30%
Projected Collateral Scheduled Amortization							3.50%	90.30%	27.60%		8.00%	37.10%	22.80%		60.00%	100.00%	95.90%		3.80%		16.00%		10.70%
Total Outstanding Collateral									100.00%				100.00%				100.00%						100.00%
LIBOR OAS																			5.26%	[2]	16.62%	[2]	10.55%	[2]
Securitized debt	$ 1,439	$ 0

[1] Includes securitized debt with a fair value of $1.4 million as of September 30, 2012.

[2] Shown in basis points.