Valuation (Schedule Of Significant Unobservable Inputs, Qualitative Information) (Details) (USD $)	9 Months Ended		12 Months Ended
	Sep. 30, 2013		Dec. 31, 2012
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Securitized debt	$ 1,038,000		$ 1,335,000
Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	800,092,000		599,914,000
Level 3 [Member] | Market Approach Valuation Technique [Member] | Private Label Residential Mortgage Backed Securities, Other asset-backed securities, and Securitized Debt [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	618,124,000	[1]
Level 3 [Member] | Market Approach Valuation Technique [Member] | Private Label Residential Mortgage Backed Securities, Other asset-backed securities, and Securitized Debt [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Non Binding Indicative Price	1.80	[1]
Level 3 [Member] | Market Approach Valuation Technique [Member] | Private Label Residential Mortgage Backed Securities, Other asset-backed securities, and Securitized Debt [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Non Binding Indicative Price	145.25	[1]
Level 3 [Member] | Market Approach Valuation Technique [Member] | Private Label Residential Mortgage Backed Securities, Other asset-backed securities, and Securitized Debt [Member] | Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Non Binding Indicative Price	79.48	[1]
Level 3 [Member] | Market Approach Valuation Technique [Member] | Private Label Commercial Mortgage-Backed Securities And Commercial Mortgage Loans [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	38,221,000
Level 3 [Member] | Market Approach Valuation Technique [Member] | Private Label Commercial Mortgage-Backed Securities And Commercial Mortgage Loans [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Non Binding Indicative Price	15.13
Level 3 [Member] | Market Approach Valuation Technique [Member] | Private Label Commercial Mortgage-Backed Securities And Commercial Mortgage Loans [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Non Binding Indicative Price	100.33
Level 3 [Member] | Market Approach Valuation Technique [Member] | Private Label Commercial Mortgage-Backed Securities And Commercial Mortgage Loans [Member] | Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Non Binding Indicative Price	73.84
Level 3 [Member] | Market Approach Valuation Technique [Member] | Agency Interest Only Residential Mortgage-Backed Securities [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	32,385,000
Level 3 [Member] | Market Approach Valuation Technique [Member] | Agency Interest Only Residential Mortgage-Backed Securities [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Non Binding Indicative Price	6.42
Level 3 [Member] | Market Approach Valuation Technique [Member] | Agency Interest Only Residential Mortgage-Backed Securities [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Non Binding Indicative Price	29.63
Level 3 [Member] | Market Approach Valuation Technique [Member] | Agency Interest Only Residential Mortgage-Backed Securities [Member] | Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Non Binding Indicative Price	14.59
Level 3 [Member] | Income Approach Valuation Technique [Member] | Private Label Residential Mortgage Backed Securities and Securitized Debt [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value			527,031,000	[2]
Level 3 [Member] | Income Approach Valuation Technique [Member] | Private Label Residential Mortgage Backed Securities and Securitized Debt [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield			2.60%	[2]
Projected Collateral Prepayments			0.70%	[2]
Projected Collateral Losses			3.70%	[2]
Projected Collateral Recoveries			0.00%	[2]
Projected Collateral Scheduled Amortization			4.10%	[2]
Level 3 [Member] | Income Approach Valuation Technique [Member] | Private Label Residential Mortgage Backed Securities and Securitized Debt [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield			29.10%	[2]
Projected Collateral Prepayments			64.60%	[2]
Projected Collateral Losses			79.70%	[2]
Projected Collateral Recoveries			41.00%	[2]
Projected Collateral Scheduled Amortization			90.40%	[2]
Level 3 [Member] | Income Approach Valuation Technique [Member] | Private Label Residential Mortgage Backed Securities and Securitized Debt [Member] | Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield			7.80%	[2]
Projected Collateral Prepayments			22.70%	[2]
Projected Collateral Losses			28.00%	[2]
Projected Collateral Recoveries			21.40%	[2]
Projected Collateral Scheduled Amortization			27.90%	[2]
Total Outstanding Collateral			100.00%	[2]
Level 3 [Member] | Income Approach Valuation Technique [Member] | Private Label Residential Mortgage-Backed Securities [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	78,075,000
Level 3 [Member] | Income Approach Valuation Technique [Member] | Private Label Residential Mortgage-Backed Securities [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield	5.80%
Projected Collateral Prepayments	6.20%
Projected Collateral Losses	1.80%
Projected Collateral Recoveries	0.20%
Projected Collateral Scheduled Amortization	13.50%
Level 3 [Member] | Income Approach Valuation Technique [Member] | Private Label Residential Mortgage-Backed Securities [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield	21.70%
Projected Collateral Prepayments	64.60%
Projected Collateral Losses	44.60%
Projected Collateral Recoveries	19.60%
Projected Collateral Scheduled Amortization	88.50%
Level 3 [Member] | Income Approach Valuation Technique [Member] | Private Label Residential Mortgage-Backed Securities [Member] | Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield	7.80%
Projected Collateral Prepayments	34.40%
Projected Collateral Losses	18.80%
Projected Collateral Recoveries	10.80%
Projected Collateral Scheduled Amortization	36.00%
Total Outstanding Collateral	100.00%
Level 3 [Member] | Income Approach Valuation Technique [Member] | Credit Default Swaps On Asset Backed Securities [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	17,296,000		36,030,000
Level 3 [Member] | Income Approach Valuation Technique [Member] | Credit Default Swaps On Asset Backed Securities [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Projected Collateral Prepayments	19.20%		8.70%
Projected Collateral Losses	17.10%		20.40%
Projected Collateral Recoveries	8.00%		12.20%
Projected Collateral Scheduled Amortization	16.00%		9.80%
Level 3 [Member] | Income Approach Valuation Technique [Member] | Credit Default Swaps On Asset Backed Securities [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Projected Collateral Prepayments	57.00%		44.10%
Projected Collateral Losses	49.40%		57.10%
Projected Collateral Recoveries	15.40%		32.80%
Projected Collateral Scheduled Amortization	40.50%		35.50%
Level 3 [Member] | Income Approach Valuation Technique [Member] | Credit Default Swaps On Asset Backed Securities [Member] | Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Projected Collateral Prepayments	28.50%		18.70%
Projected Collateral Losses	36.80%		37.80%
Projected Collateral Recoveries	13.10%		19.30%
Projected Collateral Scheduled Amortization	21.60%		24.20%
Total Outstanding Collateral	100.00%		100.00%
Level 3 [Member] | Income Approach Valuation Technique [Member] | Private Label Commercial Mortgage-Backed Securities And Commercial Mortgage Loans [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value			28,873,000
Level 3 [Member] | Income Approach Valuation Technique [Member] | Private Label Commercial Mortgage-Backed Securities And Commercial Mortgage Loans [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield			5.20%
Projected Collateral Losses			0.00%
Projected Collateral Recoveries			0.00%
Projected Collateral Scheduled Amortization			0.00%
Level 3 [Member] | Income Approach Valuation Technique [Member] | Private Label Commercial Mortgage-Backed Securities And Commercial Mortgage Loans [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield			17.90%
Projected Collateral Losses			25.10%
Projected Collateral Recoveries			88.90%
Projected Collateral Scheduled Amortization			100.00%
Level 3 [Member] | Income Approach Valuation Technique [Member] | Private Label Commercial Mortgage-Backed Securities And Commercial Mortgage Loans [Member] | Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield			9.50%
Projected Collateral Losses			3.90%
Projected Collateral Recoveries			20.50%
Projected Collateral Scheduled Amortization			75.60%
Total Outstanding Collateral			100.00%
Level 3 [Member] | Income Approach Valuation Technique [Member] | Commercial Mortgage Loans [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	9,986,000
Level 3 [Member] | Income Approach Valuation Technique [Member] | Commercial Mortgage Loans [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield	15.00%
Months to Resolution	8 months
Level 3 [Member] | Income Approach Valuation Technique [Member] | Commercial Mortgage Loans [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield	15.00%
Months to Resolution	10 months
Level 3 [Member] | Income Approach Valuation Technique [Member] | Commercial Mortgage Loans [Member] | Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield	15.00%
Months to Resolution	9 months
Level 3 [Member] | Income Approach Valuation Technique [Member] | Agency Interest Only Residential Mortgage-Backed Securities [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	$ 4,648,000		$ 6,644,000
Level 3 [Member] | Income Approach Valuation Technique [Member] | Agency Interest Only Residential Mortgage-Backed Securities [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Projected Collateral Prepayments	76.80%		81.00%
Projected Collateral Scheduled Amortization	0.00%		0.00%	[3]
LIBOR OAS	4.08%	[4]	8.16%	[4]
Level 3 [Member] | Income Approach Valuation Technique [Member] | Agency Interest Only Residential Mortgage-Backed Securities [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Projected Collateral Prepayments	100.00%		100.00%
Projected Collateral Scheduled Amortization	23.20%		19.00%	[3]
LIBOR OAS	6.49%	[4]	75.58%	[4]
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]
Projected Collateral Prepayments	92.40%		92.70%
Projected Collateral Scheduled Amortization	7.60%		7.30%	[3]
LIBOR OAS	6.19%	[4]	11.89%	[4]
Total Outstanding Collateral	100.00%		100.00%

[1] Includes securitized debt with a fair value of $1.0 million as of September 30, 2013.

[2] Includes securitized debt with a fair value of $1.3 million as of December 31, 2012.

[3] For simplicity of presentation, net negative amortization is disregarded.

[4] Shown in basis points.