To Be Announced RMBS (Details) - USD ($) $ in Thousands	Dec. 31, 2015		Dec. 31, 2014
To Be Announced Securities [Line Items]
Fair Value	$ 1,661,118		$ 2,172,082
Financial Instruments Sold, Not yet Purchased, at Fair Value	(728,747)		(1,291,370)
Payable for securities purchased	(165,365)		(98,747)
To Be Announced Fixed Rate Agency Securities [Member]
To Be Announced Securities [Line Items]
Fair Value	98,009	[1],[2],[3]	72,410	[4],[5],[6],[7]
Investment Owned, Balance, Principal Amount	94,602		71,598
Receivable for securities sold	613,023		1,205,779
TBA - Fixed Rate Agency Securities Sold Short [Member]
To Be Announced Securities [Line Items]
Financial Instruments Sold, Not yet Purchased, at Fair Value	(612,777)	[2],[8]	(1,209,539)	[5],[6],[9]
Investment Sold, Not yet Purchased, Balance, Principal Amount	(580,992)		(1,135,218)
Payable for securities purchased	(98,049)		(71,832)
Investment Owned At Fair Value, Net	$ (514,768)		$ (1,137,129)

[1] 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.

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

[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 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%

[4] At December 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 100.30%, 53.97%, and 9.33% of equity, respectively.

[5] Conformed to current period presentation.

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

[7] 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 163.60%A/A/A 0.98%Baa/BBB/BBB 5.62%Ba/BB/BB or below 80.65%Unrated 24.61%

[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.

[9] At December 31, 2014, the Company's short investments guaranteed by the Federal National Mortgage Association and the Federal Home Loan Mortgage Corporation, represented 121.95% and 31.44% of equity, respectively.