Valuation (Schedule Of Significant Unobservable Inputs, Qualitative Information) (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2013		Dec. 31, 2012
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Securitized debt	1,205,000		1,335,000
Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	627,575,000		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	501,742,000	[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	1.31	[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	151.77	[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	79.13	[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	10,728,000
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	75.89
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	99.00
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	90.50
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	16,228,000
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	6.58
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	23.14
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	14.48
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	66,511,000
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	4.70%
Projected Collateral Prepayments	0.70%
Projected Collateral Losses	14.60%
Projected Collateral Recoveries	2.30%
Projected Collateral Scheduled Amortization	9.40%
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	17.90%
Projected Collateral Prepayments	51.00%
Projected Collateral Losses	48.60%
Projected Collateral Recoveries	34.30%
Projected Collateral Scheduled Amortization	67.20%
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	8.60%
Projected Collateral Prepayments	24.50%
Projected Collateral Losses	27.50%
Projected Collateral Recoveries	19.00%
Projected Collateral Scheduled Amortization	29.00%
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	26,396,000		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	8.90%		8.70%
Projected Collateral Losses	20.20%		20.40%
Projected Collateral Recoveries	13.20%		12.20%
Projected Collateral Scheduled Amortization	10.20%		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	44.50%		44.10%
Projected Collateral Losses	56.60%		57.10%
Projected Collateral Recoveries	32.80%		32.80%
Projected Collateral Scheduled Amortization	35.90%		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	14.60%		18.70%
Projected Collateral Losses	46.40%		37.80%
Projected Collateral Recoveries	24.80%		19.30%
Projected Collateral Scheduled Amortization	14.20%		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	4,763,000	[3]
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%	[3]
Recovery Timeline	3 months	[3],[4]
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%	[3]
Recovery Timeline	3 months	[3],[4]
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%	[3]
Recovery Timeline	3 months	[3],[4]
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			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			81.00%
Projected Collateral Scheduled Amortization			0.00%	[5]
LIBOR OAS			8.16%	[6]
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%
Projected Collateral Scheduled Amortization			19.00%	[5]
LIBOR OAS			75.58%	[6]
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			92.70%
Projected Collateral Scheduled Amortization			7.30%	[5]
LIBOR OAS			11.89%	[6]
Total Outstanding Collateral			100.00%

[1] Includes securitized debt with a fair value of $1.2 million as of March 31, 2013.

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

[3] Represents non-performing commercial whole loan.

[4] Represented in number of months.

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

[6] Shown in basis points.