Significant Accounting Policies (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2014		Dec. 31, 2013
Significant Accounting Policies [Line Items]
Number of days to determine non-performance of loan	90 days
Percentage of open reserve repurchase agreements	36.00%		39.00%
Number of counterparties	2		2
Fair value of asset subject to resecuritization	$ 2,300,000		$ 2,300,000
Fair Value	1,756,011,000		1,730,130,000
Receivable for securities sold	832,841,000		883,005,000
Investments sold short, at fair value-	(818,765,000)		(845,614,000)
Payable for securities purchased	231,809,000		193,047,000
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	190,446,000	[1],[2],[3],[4]	96,856,000	[1],[5],[6],[7]
Receivable for securities sold	784,300,000		813,900,000
TBA - Fixed Rate Agency Securities Sold Short [Member]
Significant Accounting Policies [Line Items]
Investments sold short, at fair value-	(782,747,000)	[1],[4],[8]	(811,957,000)	[1],[6],[9]
Payable for securities purchased	190,300,000		96,800,000
Net short position, TBA	$ (592,300,000)		$ (715,100,000)
Maximum [Member]
Significant Accounting Policies [Line Items]
Reverse repurchase agreements remaining terms	180 days		180 days
Reverse repurchase agreements interest rate	2.24%		2.27%
Maximum [Member] | Long-Term Incentive Plan Units [Member] | Dedicated or partially dedicated personnel [Member]
Significant Accounting Policies [Line Items]
Vesting period	2 years
Minimum [Member]
Significant Accounting Policies [Line Items]
Reverse repurchase agreements remaining terms	2 days		2 days
Reverse repurchase agreements interest rate	0.30%		0.32%
Minimum [Member] | Long-Term Incentive Plan Units [Member] | Dedicated or partially dedicated personnel [Member]
Significant Accounting Policies [Line Items]
Vesting period	1 year
Weighted Average [Member]
Significant Accounting Policies [Line Items]
Reverse repurchase agreements remaining terms	59 days		56 days
Reverse repurchase agreements interest rate	0.76%		0.90%
Forwards [Member]
Significant Accounting Policies [Line Items]
Percentage of average monthly notional amount	132.00%
Option contract [Member]
Significant Accounting Policies [Line Items]
Percentage of average monthly notional amount	51.00%		387.00%
Interest Rate Swaps [Member]
Significant Accounting Policies [Line Items]
Percentage of average monthly notional amount	96.00%		187.00%
Total Return Swaps [Member]
Significant Accounting Policies [Line Items]
Percentage of average monthly notional amount	83.00%		210.00%
Credit Default Swaps [Member]
Significant Accounting Policies [Line Items]
Percentage of average monthly notional amount	94.00%		174.00%
Futures [Member]
Significant Accounting Policies [Line Items]
Percentage of average monthly notional amount	129.00%		179.00%
JP Morgan Prime Money Market Premier Fund [Member]
Significant Accounting Policies [Line Items]
Fair Value, Concentration of Risk, Cash and Cash Equivalents	29.00%		27.00%
Bank of New York Mellon Corporation [Member]
Significant Accounting Policies [Line Items]
Fair Value, Concentration of Risk, Cash and Cash Equivalents	71.00%		73.00%

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

[2] At March 31, 2014, 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 124.05%, 41.24%, and 12.18% of equity, respectively.

[3] 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 the Federal National Mortgage Association, the Federal Home Loan Mortgage Corporation, or the Government National Mortgage Association. 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 of EquityUnrated but Agency-Guaranteed 177.47%A/A/A 0.03%Baa/BBB/BBB 2.31%Ba/BB/BB or below 84.29%Unrated 14.60%

[4] The following table details the breakout by geographical region of long investments, investments sold short, repurchase agreements, and financial derivatives–assets. All financial derivatives–liabilities were concentrated in North America.Region Current Principal/Notional Value/Number of Shares/Number of Properties Cost/(Proceeds) Fair Value Percent ofEquityLong Investments: (In thousands, Expressed in U.S. Dollars) North America 2,449,649 $1,686,738 $1,729,893 274.55 %Europe 32,195 26,451 26,118 4.15 %Total 2,481,844 $1,713,189 $1,756,011 278.70 %Investments Sold Short: North America (TBAs and Government Debt) (756,627) $(789,167) $(787,667) (125.01)%Europe (Government Debt) (22,208) (23,481) (24,195) (3.84)%North America (Common Stock) (941) (7,004) (6,903) (1.10)%Total $(819,652) $(818,765) (129.95)%Repurchase Agreements: North America 4,944 $4,944 $4,944 0.78 %Europe 24,931 24,928 24,931 3.96 %Total 29,875 $29,872 $29,875 4.74 %Financial Derivatives–Assets: North America (583,909) $55,230 $57,558 9.14 %Europe (8,980) — 2 — %Total (592,889) $55,230 $57,560 9.14 %

[5] 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.

[6] The following table details the breakout by geographical region of long investments, investments sold short, and repurchase agreements. All financial derivatives were concentrated in North America.Region Current Principal/Number of Shares Cost/(Proceeds) 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 %

[7] 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 the Federal National Mortgage Association, the Federal Home Loan Mortgage Corporation, or the Government National Mortgage Association. 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%

[8] At March 31, 2014, the Company's short investments guaranteed by the Federal National Mortgage Association and the Federal Home Loan Mortgage Corporation represented 104.70% and 19.53% of equity, respectively.

[9] 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.