Financial Instruments With Off-Balance Sheet Risk Or Concentrations Of Credit Risk	12 Months Ended
Dec. 31, 2011
Financial Instruments With Off-Balance Sheet Risk Or Concentrations Of Credit Risk [Abstract]
Financial Instruments With Off-Balance Sheet Risk Or Concentrations Of Credit Risk	12. FINANCIAL INSTRUMENTS WITH OFF-BALANCE SHEET RISK OR CONCENTRATIONS OF CREDIT RISK In the normal course of its business, the Company trades various financial instruments and enters into various investment activities with off-balance sheet risk, including interest rate swap contracts. These financial instruments contain varying degrees of off-balance sheet risk whereby losses resulting from changes in the fair values of the securities underlying the financial instruments or the Company's obligations thereunder may ultimately exceed the amount recognized in the statement of assets and liabilities. The notional amounts of the swap contracts do not represent the Company's risk of loss due to counterparty nonperformance. The Company's exposure to credit risk associated with counterparty nonperformance on swap contracts is limited to the unrealized gains, if any, inherent in such contracts which are recognized in the statement of assets and liabilities. Any counterparty nonperformance of these transactions is not expected to have a material effect on the Company's financial condition. The Company's investments are primarily concentrated in securities that pass through collections of principal and interest from underlying mortgages, and there is a risk that some borrowers on the underlying mortgages will default. Therefore, mortgage-backed securities may bear some exposure to credit losses. However, the Company mitigates credit risk by primarily holding securities that are either guaranteed by government (or government-sponsored) agencies. The Company bears certain other risks typical in investing in a portfolio of mortgage-backed securities. The principal risks potentially affecting the Company's financial position, results of operations and cash flows include the risks that: (a) interest rate changes can negatively affect the fair value of the Company's mortgage-backed securities, (b) interest rate changes can influence borrowers' decisions to prepay the mortgages underlying the securities, which can negatively affect both cash flows from, and the fair value of, the securities, and (c) adverse changes in the fair value of the Company's mortgage-backed securities and/or the inability of the Company to renew short term borrowings under repurchase agreements can result in the need to sell securities at inopportune times and incur realized losses. The Company enters into derivative transactions with counterparties as hedges of interest rate exposure and in the course of investing. In the event of nonperformance by a counterparty, the Company is potentially exposed to losses, although the counterparties to these agreements are primarily major financial institutions with investment grade ratings. The Company is subject to interest rate risk. Generally, the value of fixed income securities will change inversely with changes in interest rates. As interest rates rise, the market value of fixed income securities tends to decrease. Conversely, as interest rates fall, the market value of fixed income securities tends to increase. The Company's principal trading activities are primarily with brokers and other financial institutions located in North America. All securities transactions of the Company are cleared by multiple major securities firms pursuant to customer agreements. At December 31, 2011 and 2010, substantially all the investments in securities and receivable for securities sold are positions with and amounts due from these brokers. The Company had substantially all of its individual counterparty concentrations with these brokers and their affiliates.

12. FINANCIAL INSTRUMENTS WITH OFF-BALANCE SHEET RISK OR CONCENTRATIONS OF CREDIT RISK

In the normal course of its business, the Company trades various financial instruments and enters into various investment activities with off-balance sheet risk, including interest rate swap contracts. These financial instruments contain varying degrees of off-balance sheet risk whereby losses resulting from changes in the fair values of the securities underlying the financial instruments or the Company's obligations thereunder may ultimately exceed the amount recognized in the statement of assets and liabilities.

The notional amounts of the swap contracts do not represent the Company's risk of loss due to counterparty nonperformance. The Company's exposure to credit risk associated with counterparty nonperformance on swap contracts is limited to the unrealized gains, if any, inherent in such contracts which are recognized in the statement of assets and liabilities. Any counterparty nonperformance of these transactions is not expected to have a material effect on the Company's financial condition.

The Company's investments are primarily concentrated in securities that pass through collections of principal and interest from underlying mortgages, and there is a risk that some borrowers on the underlying mortgages will default. Therefore, mortgage-backed securities may bear some exposure to credit losses. However, the Company mitigates credit risk by primarily holding securities that are either guaranteed by government (or government-sponsored) agencies.

The Company bears certain other risks typical in investing in a portfolio of mortgage-backed securities. The principal risks potentially affecting the Company's financial position, results of operations and cash flows include the risks that: (a) interest rate changes can negatively affect the fair value of the Company's mortgage-backed securities, (b) interest rate changes can influence borrowers' decisions to prepay the mortgages underlying the securities, which can negatively affect both cash flows from, and the fair value of, the securities, and (c) adverse changes in the fair value of the Company's mortgage-backed securities and/or the inability of the Company to renew short term borrowings under repurchase agreements can result in the need to sell securities at inopportune times and incur realized losses.

The Company enters into derivative transactions with counterparties as hedges of interest rate exposure and in the course of investing. In the event of nonperformance by a counterparty, the Company is potentially exposed to losses, although the counterparties to these agreements are primarily major financial institutions with investment grade ratings.

The Company is subject to interest rate risk. Generally, the value of fixed income securities will change inversely with changes in interest rates. As interest rates rise, the market value of fixed income securities tends to decrease. Conversely, as interest rates fall, the market value of fixed income securities tends to increase.

The Company's principal trading activities are primarily with brokers and other financial institutions located in North America. All securities transactions of the Company are cleared by multiple major securities firms pursuant to customer agreements. At December 31, 2011 and 2010, substantially all the investments in securities and receivable for securities sold are positions with and amounts due from these brokers. The Company had substantially all of its individual counterparty concentrations with these brokers and their affiliates.