To Be Announced RMBS (Details) - USD ($) $ in Thousands	Mar. 31, 2016		Dec. 31, 2015
To Be Announced Securities [Line Items]
Fair Value	$ 1,625,585		$ 1,661,118
Financial Instruments Sold, Not yet Purchased, at Fair Value	(712,128)		(728,747)
Payable for securities purchased	(103,376)		(165,365)
To Be Announced Fixed Rate Agency Securities [Member]
To Be Announced Securities [Line Items]
Fair Value	74,886	[1],[2],[3]	98,009	[4],[5],[6]
Investment Owned, Balance, Principal Amount	71,245		94,602
Receivable for securities sold	569,375		613,023
TBA - Fixed Rate Agency Securities Sold Short [Member]
To Be Announced Securities [Line Items]
Financial Instruments Sold, Not yet Purchased, at Fair Value	(571,063)	[2],[7]	(612,777)	[5],[8]
Investment Sold, Not yet Purchased, Balance, Principal Amount	(535,080)		(580,992)
Payable for securities purchased	(74,681)		(98,049)
Investment Owned At Fair Value, Net	$ (496,177)		$ (514,768)

[1] At March 31, 2016, 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 78.59%, 42.93%, and 24.06% of equity, respectively.

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

[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 145.58%Aaa/AAA/AAA 1.97%A/A/A 0.32%Baa/BBB/BBB 0.88%Ba/BB/BB or below 30.77%Unrated 54.40%

[4] At December 31, 2015, 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 77.17%, 47.44%, and 18.91% of equity, respectively.

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

[6] 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 of EquityUnrated but Agency-Guaranteed 143.52%A/A/A 0.32%Baa/BBB/BBB 1.07%Ba/BB/BB or below 34.89%Unrated 44.99%

[7] At March 31, 2016, the Company's short investments guaranteed by the Federal National Mortgage Association, the Federal Home Loan Mortgage Corporation, and the Government National Mortgage Association, represented 57.42%, 18.46%, and 6.30% of equity, respectively.

[8] At December 31, 2015, the Company's short investments guaranteed by the Federal National Mortgage Association, the Federal Home Loan Mortgage Corporation, and the Government National Mortgage Association, represented 57.51%, 23.25%, and 2.17% of equity, respectively.