Slicers (applies to each fact value in each table cell)

Reporting Entity [Axis]

0001560672 (http://www.sec.gov/CIK)

Fair Value Disclosures [Abstract]	Period [Axis]
	2016-01-01 - 2016-12-31
Fair Value Disclosures [Abstract]
Schedule of Fair Value Measurements	The following tables present the Company's financial instruments measured at fair value on: December 31, 2016: (In thousands)                 Description   Level 1   Level 2   Level 3   Total Assets:                 Mortgage-backed securities, at fair value:                 Agency RMBS:                 15-year fixed rate mortgages   $ —   $ 148,363   $ —   $ 148,363 20-year fixed rate mortgages   —   11,185   —   11,185 30-year fixed rate mortgages   —   940,457   —   940,457 Adjustable rate mortgages   —   33,138   —   33,138 Reverse mortgages   —   62,058   —   62,058 Interest only securities   —   —   12,347   12,347 Non-Agency RMBS   —   12,948   6,498   19,446 Mortgage-backed securities, at fair value   —   1,208,149   18,845   1,226,994 Financial derivatives–assets, at fair value:                 TBAs   —   1,045   —   1,045 Interest rate swaps   —   4,891   —   4,891 Futures   72   —   —   72 Total financial derivatives–assets, at fair value   72   5,936   —   6,008 Total mortgage-backed securities and financial derivatives–assets, at fair value   $ 72   $ 1,214,085   $ 18,845   $ 1,233,002 Liabilities:                 U.S. Treasury securities sold short, at fair value   $ —   $ (74,194 )   $ —   $ (74,194 ) Financial derivatives–liabilities, at fair value:                 TBAs   —   (554 )   —   (554 ) Interest rate swaps   —   (1,421 )   —   (1,421 ) Total financial derivatives–liabilities, at fair value   —   (1,975 )   —   (1,975 ) Total U.S. Treasury securities sold short and financial derivatives–liabilities, at fair value   $ —   $ (76,169 )   $ —   $ (76,169 ) December 31, 2015: (In thousands)                 Description   Level 1   Level 2   Level 3   Total Assets:                 Mortgage-backed securities, at fair value:                 Agency RMBS:                 15-year fixed rate mortgages   $ —   $ 170,261   $ —   $ 170,261 20-year fixed rate mortgages   —   19,830   —   19,830 30-year fixed rate mortgages   —   900,794   —   900,794 Adjustable rate mortgages   —   38,530   —   38,530 Reverse mortgages   —   73,692   —   73,692 Interest only securities   —   —   7,758   7,758 Non-Agency RMBS   —   27,381   4,020   31,401 Mortgage-backed securities, at fair value   —   1,230,488   11,778   1,242,266 Financial derivatives–assets, at fair value:                 TBAs   —   417   —   417 Interest rate swaps   —   1,748   —   1,748 Futures   18   —   —   18 Total financial derivatives–assets, at fair value   18   2,165   —   2,183 Total mortgage-backed securities and financial derivatives–assets, at fair value   $ 18   $ 1,232,653   $ 11,778   $ 1,244,449 Liabilities:                 U.S. Treasury securities sold short, at fair value   $ —   $ (78,447 )   $ —   $ (78,447 ) Financial derivatives–liabilities, at fair value:                 TBAs   —   (364 )   —   (364 ) Interest rate swaps   —   (4,361 )   —   (4,361 ) Total financial derivatives–liabilities, at fair value   —   (4,725 )   —   (4,725 ) Total U.S. Treasury securities sold short and financial derivatives–liabilities, at fair value   $ —   $ (83,172 )   $ —   $ (83,172 )
Unobservable Input Reconciliation	The following tables present additional information about the Company's investments which are measured at fair value for which the Company has utilized Level 3 inputs to determine fair value: Year ended December 31, 2016: (In thousands) Non-Agency RMBS   Agency RMBS Beginning balance as of December 31, 2015 $ 4,020   $ 7,758 Purchases 2,608   7,188 Proceeds from sales (1,270 )   — Principal repayments (1,256 )   — (Amortization)/accretion, net 344   (3,535 ) Net realized gains (losses) 1,079   (303 ) Change in net unrealized gains (losses) (571 )   1,239 Transfers:       Transfers into level 3 3,120   — Transfers out of level 3 (1,576 )   — Ending balance as of December 31, 2016 $ 6,498   $ 12,347 All amounts of net realized and changes in net unrealized gains (losses) in the table above are reflected in the accompanying Consolidated Statement of Operations. The table above incorporates changes in net unrealized gains (losses) for both Level 3 financial instruments held by the Company at December 31, 2016, as well as Level 3 financial instruments disposed of by the Company during the year ended December 31, 2016. For Level 3 financial instruments held by the Company as of December 31, 2016, change in net unrealized gains (losses) of $0.8 million and $1.1 million, for the year ended December 31, 2016 relate to non-Agency RMBS and Agency RMBS, respectively. During the year ended December 31, 2016, the Company transferred $1.6 million of non-Agency RMBS from Level 3 to Level 2. These assets were transferred from Level 3 to Level 2 based on an increased volume of observed trading of these and/or similar assets. This increase in observed trading activity has led to greater price transparency for these assets, thereby making a Level 2 designation appropriate in the Company's view. However, changes in the volume of observable inputs for these assets, such as a decrease in the volume of observed trading, could impact price transparency, and thereby cause a change in the level designation for these assets in future periods. During the year ended December 31, 2016, the Company transferred $3.1 million of non-Agency RMBS from Level 2 to Level 3. Since December 31, 2015, these securities have exhibited indications of a reduced level of price transparency. Examples of such indications include wider spreads and/or higher delinquencies relative to similar securities and a reduction in observable transactions or executable quotes involving these and similar securities. Changes in these indications could impact price transparency, and thereby cause a change in the level designation in future periods. Year ended December 31, 2015: (In thousands) Non-Agency RMBS   Agency RMBS Beginning balance as of December 31, 2014 $ 10,082   $ 11,244 Purchases —   4,360 Proceeds from sales (2,861 )   (4,538 ) Principal repayments (1,765 )   — (Amortization)/accretion, net 1,371   (2,714 ) Net realized gains (losses) 791   602 Change in net unrealized gains (losses) (496 )   (1,196 ) Transfers:       Transfers into level 3 1,681   — Transfers out of level 3 (4,783 )   — Ending balance as of December 31, 2015 $ 4,020   $ 7,758 All amounts of net realized and changes in net unrealized gains (losses) in the table above are reflected in the accompanying Consolidated Statement of Operations. The table above incorporates changes in net unrealized gains (losses) for both Level 3 financial instruments held by the Company as of December 31, 2015, as well as Level 3 financial instruments disposed of by the Company during the year ended December 31, 2015. For Level 3 financial instruments held by the Company as of December 31, 2015, change in net unrealized gains (losses) of $(0.3) million and $(0.3) million, for the year ended December 31, 2015 relate to non-Agency RMBS and Agency RMBS, respectively. During the year ended December 31, 2015, the Company transferred $4.8 million of non-Agency RMBS from Level 3 to Level 2. These assets were transferred from Level 3 to Level 2 based on an increased volume of observed trading of these and/or similar assets. This increase in observed trading activity has led to greater price transparency for these assets, thereby making a Level 2 designation appropriate in the Company's view. However, changes in the volume of observable inputs for these assets, such as a decrease in the volume of observed trading, could impact price transparency, and thereby cause a change in the level designation for these assets in future periods. During the year ended December 31, 2015, the Company transferred $1.7 million of non-Agency RMBS from Level 2 to Level 3. Following December 31, 2014, these securities exhibited indications of a reduced level of price transparency. Examples of such indications include wider spreads and/or higher delinquencies relative to similar securities and a reduction in observable transactions or executable quotes involving these and similar securities. Changes in these indications could impact price transparency, and thereby cause a change in the level designation in future periods. Year ended December 31, 2014: (In thousands) Non-Agency RMBS   Agency RMBS Beginning balance as of December 31, 2013 $ 30,681   $ 13,527 Purchases 14,712   4,853 Proceeds from sales (11,104 )   (2,330 ) Principal repayments (5,443 )   — (Amortization)/accretion, net 1,930   (3,136 ) Net realized gains (losses) 1,518   676 Change in net unrealized gains (losses) 207   (2,346 ) Transfers:       Transfers into level 3 —   — Transfers out of level 3 (22,419 )   — Ending balance as of December 31, 2014 $ 10,082   $ 11,244 All amounts of net realized and changes in net unrealized gains (losses) in the table above are reflected in the accompanying Consolidated Statement of Operations. The table above incorporates changes in net unrealized gains (losses) for both Level 3 financial instruments held by the Company as of December 31, 2014, as well as Level 3 financial instruments disposed of by the Company during the year ended December 31, 2014. For Level 3 financial instruments held by the Company as of December 31, 2014, change in net unrealized gains (losses) of $0.7 million and $(2.0) million, for the year ended December 31, 2014 relate to non-Agency RMBS and Agency RMBS, respectively. At December 31, 2014, the Company transferred $22.4 million of non-Agency RMBS from Level 3 to Level 2. The decision to transfer these assets from Level 3 to Level 2 was based on observed market developments, including an increased volume of buying and selling of these and/or similar assets, greater consensus among market participants on price based on market quotes, and generally tighter credit spreads driven by improved performance in the underlying collateral as well as increased demand from investors seeking higher yielding assets. These factors have led to greater price transparency for these assets, thereby making a Level 2 designation appropriate in the Company's view. However, changes in observed market developments could impact future price transparency, and thereby cause a change in the level designation in subsequent periods.
Quantitative Information	The following tables identify the significant unobservable inputs that affect the valuation of the Company's Level 3 assets and liabilities as of December 31, 2016 and 2015: December 31, 2016:     Range     Description   Fair Value   Valuation Technique   Significant Unobservable Input   Min   Max   Weighted Average(1)     (In thousands)                     Non-Agency RMBS   $ 652   Discounted Cash Flows   Yield   30.6 %   30.6 %   30.6 %             Projected Collateral Prepayments   49.0 %   49.0 %   49.0 %             Projected Collateral Losses   1.0 %   1.0 %   1.0 %             Projected Collateral Recoveries   3.3 %   3.3 %   3.3 %             Projected Collateral Scheduled Amortization   46.7 %   46.7 %   46.7 %                         100.0 % Non-Agency RMBS   5,846   Market quotes   Non-Binding Third-Party Valuation   $ 46.40   $ 63.29   $ 56.49 Agency RMBS–Interest Only Securities   8,784   Market quotes   Non-Binding Third-Party Valuation   $ 3.94   $ 21.56   $ 13.96 Agency RMBS–Interest Only Securities   3,563   Option Adjusted Spread ("OAS")   LIBOR OAS (2)   103   1,147   468             Projected Collateral Prepayments   51.1 %   85.4 %   70.9 %             Projected Collateral Scheduled Amortization   14.6 %   48.9 %   29.1 %                         100.0 % (1) Averages are weighted based on the fair value of the related instrument. (2) Shown in basis points. December 31, 2015:     Range     Description   Fair Value   Valuation Technique   Significant Unobservable Input   Min   Max   Weighted Average(1)     (In thousands)                     Non-Agency RMBS   $ 4,020   Discounted Cash Flows   Yield   8.8 %   25.7 %   13.4 %             Projected Collateral Prepayments   32.5 %   68.7 %   60.5 %             Projected Collateral Losses   1.3 %   9.0 %   5.3 %             Projected Collateral Recoveries   3.4 %   9.2 %   6.4 %             Projected Collateral Scheduled Amortization   13.1 %   60.1 %   27.8 %                         100.0 % Agency RMBS–Interest Only Securities   5,645   Market quotes   Non-Binding Third-Party Valuation   $ 4.39   $ 21.63   $ 11.88 Agency RMBS–Interest Only Securities   2,113   Option Adjusted Spread ("OAS")   LIBOR OAS(2)   221   984   576             Projected Collateral Prepayments   52.7 %   88.0 %   74.1 %             Projected Collateral Scheduled Amortization   12.0 %   47.3 %   25.9 %                         100.0 % (1) Averages are weighted based on the fair value of the related instrument. (2) Shown in basis points.
Fair Value, Other Financial Instruments	The following table summarizes the estimated fair value of all other financial instruments not included in the disclosures above as of December 31, 2016 and 2015:     December 31, 2016   December 31, 2015 (In thousands)   Fair Value   Carrying Value   Fair Value   Carrying Value Other financial instruments                 Assets:                 Cash and cash equivalents   $ 33,504   $ 33,504   $ 40,166   $ 40,166 Due from brokers   49,518   49,518   33,297   33,297 Reverse repurchase agreements   75,012   75,012   78,632   78,632 Liabilities:                 Repurchase agreements   1,197,973   1,197,973   1,222,719   1,222,719 Due to brokers   1,055   1,055   439   439 Cash and cash equivalents includes cash held in an interest bearing overnight account for which fair value equals the carrying value and cash held in money market accounts which are liquid in nature and for which fair value equals the carrying value; such assets are considered Level 1 assets. Due from brokers and Due to brokers include collateral transferred to or received from counterparties, along with receivables and payables for open and/or closed derivative positions. These receivables and payables are short term in nature and any collateral transferred consists primarily of cash; fair value of these items approximates carrying value and such items are considered Level 1 assets and liabilities. The Company's repurchase and reverse repurchase agreements are carried at cost, which approximates fair value due to their short term nature. Repurchase agreements and reverse repurchase agreements are classified as Level 2 assets and liabilities based on the adequacy of the collateral and their short term nature.