Significant Accounting Policies (Details) (USD $)	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012
Significant Accounting Policies [Line Items]
Number of days to determine non-performance of loan	90 days
Percentage of open reserve repurchase agreements	39.00%		67.00%
Number of counterparties	2		2
Fair value of asset subject to resecuritization	$ 2,300,000		$ 2,400,000
Fair Value	1,730,130,000		1,375,116,000
Receivable for securities sold	883,005,000		626,919,000
Investments sold short, at fair value-	(845,614,000)		(622,301,000)
Payable for securities purchased	193,047,000		57,333,000
Long-Term Incentive Plan Units [Member] | Partially dedicated personnel [Member]
Significant Accounting Policies [Line Items]
Vesting period	2 years
Long-Term Incentive Plan Units [Member] | Director [Member]
Significant Accounting Policies [Line Items]
Vesting period	1 year
Long-Term Incentive Plan Units [Member] | Manager [Member]
Significant Accounting Policies [Line Items]
LTIP vesting period	3 years
TBA - Fixed Rate Agency Securities [Member]
Significant Accounting Policies [Line Items]
Fair Value	96,856,000	[1],[2],[3],[4]	43,610,000	[1],[5],[6]
Receivable for securities sold	813,900,000		608,500,000
TBA - Fixed Rate Agency Securities Sold Short [Member]
Significant Accounting Policies [Line Items]
Investments sold short, at fair value-	(811,957,000)	[1],[2],[7]	(608,720,000)	[1],[8]
Payable for securities purchased	96,800,000		43,800,000
Net short position, TBA	$ (715,100,000)		$ (565,100,000)
Maximum [Member]
Significant Accounting Policies [Line Items]
Reverse repurchase agreements remaining terms	180 days		180 days
Reverse repurchase agreements interest rate	2.27%		2.31%
Minimum [Member]
Significant Accounting Policies [Line Items]
Reverse repurchase agreements remaining terms	2 days		10 days
Reverse repurchase agreements interest rate	0.32%		0.37%
Weighted Average [Member]
Significant Accounting Policies [Line Items]
Reverse repurchase agreements remaining terms	56 days		57 days
Reverse repurchase agreements interest rate	0.90%		0.77%
Option contract [Member]
Significant Accounting Policies [Line Items]
Percentage of average monthly notional amount	387.00%
Interest Rate Swaps [Member]
Significant Accounting Policies [Line Items]
Percentage of average monthly notional amount	187.00%		92.00%
Total Return Swaps [Member]
Significant Accounting Policies [Line Items]
Percentage of average monthly notional amount	210.00%		87.00%
Credit Default Swaps [Member]
Significant Accounting Policies [Line Items]
Percentage of average monthly notional amount	174.00%		78.00%
Futures [Member]
Significant Accounting Policies [Line Items]
Percentage of average monthly notional amount	179.00%		57.00%
JP Morgan Prime Money Market Premier Fund [Member]
Significant Accounting Policies [Line Items]
Fair Value, Concentration of Risk, Cash and Cash Equivalents	27.00%
Bank of New York Mellon Corporation [Member]
Significant Accounting Policies [Line Items]
Fair Value, Concentration of Risk, Cash and Cash Equivalents	73.00%		100.00%

[1] See Note 2 and Note 3 in Notes to Consolidated Financial Statements.

[2] The following table details the breakout by geographical region of long investments, investments sold short, and repurchase agreements:Region Current Principal/Number of Shares Cost Fair Value Percent ofEquityLong Investments: (In thousands, Expressed in U.S. Dollars) North America 2,470,650 $1,682,533 $1,724,370 275.44 %Europe 7,641 5,724 5,760 0.92 %Total 2,478,291 $1,688,257 $1,730,130 276.36 %Investments Sold Short: North America (TBAs and Government Debt) (804,888) $(833,656) $(831,564) (132.82)%Europe (Government Debt) (7,337) (7,633) (7,681) (1.23)%North America (Common Stock) (763) (6,313) (6,369) (1.02)%Total $(847,602) $(845,614) (135.07)%Repurchase Agreements: North America 19,675 $19,675 $19,675 3.15 %Europe 8,287 8,268 8,287 1.32 %Total 27,962 $27,943 $27,962 4.47 %

[3] The table below shows the ratings on the Company's long investments from Moody's, Standard and Poor's, or Fitch, as well as the Company's long investments that were unrated but guaranteed by Fannie Mae, Freddie Mac, or Ginnie Mae. Ratings tend to be a lagging credit indicator; as a result, the credit quality of the Company's long investment holdings may be lower than the credit quality implied based on the ratings listed below. In situations where an investment has a split rating, the lowest provided rating is used. The ratings descriptions include ratings qualified with a "+," "-," "1," "2," or "3."Rating Description Percent ofEquityUnrated but Agency-Guaranteed 164.58%A/A/A 0.34%Baa/BBB/BBB 2.97%Ba/BB/BB or below 97.95%Unrated 10.52%

[4] At December 31, 2013, the Company's long investments guaranteed by the Federal National Mortgage Association, the Federal Home Loan Mortgage Corporation, and the Government National Mortgage Association represented 100.85%, 51.37%, and 12.36% of equity, respectively.

[5] The table below shows the Company's long investment ratings from Moody's, Standard and Poor's, or Fitch, as well as the Company's long investments that were unrated but guaranteed by Fannie Mae, Freddie Mac, or Ginnie Mae. Ratings tend to be a lagging credit indicator; as a result, the credit quality of the Company's long investment holdings may be lower than the credit quality implied based on the ratings listed below. In situations where an investment has a split rating, the lowest provided rating is used. The ratings descriptions include ratings qualified with a "+," "-," "1," "2," or "3."Rating Description Percent ofEquityUnrated but Agency-Guaranteed 161.52%Aaa/AAA/AAA 0.01%Aa/AA/AA 0.26%A/A/A 1.02%Baa/BBB/BBB 3.70%Ba/BB/BB or below 102.40%Unrated 2.66%

[6] At December 31, 2012, the Company's long investments guaranteed by the Federal National Mortgage Association, the Federal Home Loan Mortgage Corporation, and the Government National Mortgage Association represented 119.78%, 40.49%, and 1.25% of equity, respectively.

[7] At December 31, 2013, the Company's short investments guaranteed by the Federal National Mortgage Association and the Federal Home Loan Mortgage Corporation represented 111.89% and 17.80% of equity, respectively.

[8] At December 31, 2012, the Company's short investments guaranteed by the Federal National Mortgage Association and the Federal Home Loan Mortgage Corporation represented 105.27% and 14.95% of equity, respectively.