Quarterly report pursuant to Section 13 or 15(d)

Derivative Instruments and Hedging Activities Schedule of Inverse Interest-Only Securities Reconciliation (Details)

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Derivative Instruments and Hedging Activities Schedule of Inverse Interest-Only Securities Reconciliation (Details) (USD $)
In Thousands, unless otherwise specified
 3 Months Ended 6 Months Ended
Jun. 30, 2013
Jun. 30, 2013
Jun. 30, 2014
Mar. 31, 2014
Dec. 31, 2013
Mar. 31, 2013
Dec. 31, 2012
Derivatives, Fair Value [Line Items]              
Interest Receivable     $ 50,110   $ 50,303    
Reduction of Mangement Fees 40 4,340          
Derivative, Notional Amount 44,262,605 44,262,605 43,379,217 43,576,146 37,366,610 27,041,328 22,377,656
Derivative Financial Instruments, Assets [Member]
              
Derivatives, Fair Value [Line Items]              
Derivative, Fair Value, Net     331,601   549,859    
Derivative, Notional Amount     38,499,739   30,383,908    
Inverse Interest-Only Securities [Member]
              
Derivatives, Fair Value [Line Items]              
Interest Receivable     2,488   2,855    
Derivative, Notional Amount 1,798,972 1,798,972 1,323,650 1,412,374 1,525,845 1,960,087 1,909,351
Derivative, Unamortized Premium     0   0    
Derivative, Designated Credit Reserve     0   0    
Derivative, Net, Unamortized     (1,123,574)   (1,292,785)    
Derivative, Amortized Cost Basis     200,076   233,060    
Derivative, Gross Unrealized Gains     11,542   5,891    
Derivative, Gross Unrealized Losses     (6,845)   (20,442)    
Derivative, Carrying Value     204,773   218,509    
Inverse Interest-Only Securities [Member] | Derivative Financial Instruments, Assets [Member]
              
Derivatives, Fair Value [Line Items]              
Derivative, Fair Value, Net     207,260   221,364    
Derivative, Notional Amount     $ 1,323,650   $ 1,525,845