Valuation (Schedule Of Significant Unobservable Inputs, Qualitative Information) (Details) (USD $)	6 Months Ended		12 Months Ended
	Jun. 30, 2013		Dec. 31, 2012
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Securitized debt	$ 1,168,000		$ 1,335,000
Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	814,350,000		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	678,375,000	[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	29.00	[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	149.87	[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	80.52	[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	17,202,000
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	71.35
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	100.25
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	86.60
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	22,814,000
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	6.82
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	26.84
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	14.54
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	54,807,000
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	6.10%
Projected Collateral Prepayments	0.70%
Projected Collateral Losses	4.50%
Projected Collateral Recoveries	0.00%
Projected Collateral Scheduled Amortization	12.20%
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	20.80%
Projected Collateral Prepayments	57.80%
Projected Collateral Losses	48.80%
Projected Collateral Recoveries	17.90%
Projected Collateral Scheduled Amortization	89.20%
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	10.40%
Projected Collateral Prepayments	32.20%
Projected Collateral Losses	20.30%
Projected Collateral Recoveries	8.90%
Projected Collateral Scheduled Amortization	38.60%
Total Outstanding Collateral	100.00%
Level 3 [Member] | Income Approach Valuation Technique [Member] | Private Label Commercial Mortgage-Backed Securities [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	11,717,000
Level 3 [Member] | Income Approach Valuation Technique [Member] | Private Label Commercial Mortgage-Backed Securities [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield	10.20%
Projected Collateral Losses	0.30%
Projected Collateral Recoveries	9.30%
Projected Collateral Scheduled Amortization	90.40%
Level 3 [Member] | Income Approach Valuation Technique [Member] | Private Label Commercial Mortgage-Backed Securities [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield	30.10%
Projected Collateral Losses	0.30%
Projected Collateral Recoveries	9.30%
Projected Collateral Scheduled Amortization	90.40%
Level 3 [Member] | Income Approach Valuation Technique [Member] | Private Label Commercial Mortgage-Backed Securities [Member] | Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield	15.90%
Projected Collateral Losses	0.30%
Projected Collateral Recoveries	9.30%
Projected Collateral Scheduled Amortization	90.40%
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	20,593,000		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	19.50%		8.70%
Projected Collateral Losses	18.00%		20.40%
Projected Collateral Recoveries	7.30%		12.20%
Projected Collateral Scheduled Amortization	15.60%		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	55.60%		44.10%
Projected Collateral Losses	52.30%		57.10%
Projected Collateral Recoveries	14.60%		32.80%
Projected Collateral Scheduled Amortization	36.60%		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	26.70%		18.70%
Projected Collateral Losses	40.10%		37.80%
Projected Collateral Recoveries	12.70%		19.30%
Projected Collateral Scheduled Amortization	20.50%		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	2,550,000
Level 3 [Member] | Income Approach Valuation Technique [Member] | Commercial Mortgage Loans [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield	32.30%
Recovery Timeline	12 months
Level 3 [Member] | Income Approach Valuation Technique [Member] | Commercial Mortgage Loans [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield	32.30%
Recovery Timeline	12 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	32.30%
Recovery Timeline	12 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	$ 4,583,000		$ 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	54.80%		81.00%
Projected Collateral Scheduled Amortization	13.80%		0.00%	[3]
LIBOR OAS	4.62%	[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	86.20%		100.00%
Projected Collateral Scheduled Amortization	45.20%		19.00%	[3]
LIBOR OAS	11.73%	[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	70.90%		92.70%
Projected Collateral Scheduled Amortization	29.10%		7.30%	[3]
LIBOR OAS	6.39%	[4]	11.89%	[4]
Total Outstanding Collateral	100.00%		100.00%

[1] Includes securitized debt with a fair value of $1.2 million as of June 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.