Quarterly report pursuant to Section 13 or 15(d)

Derivative Instruments and Hedging Activities Put and Call Options for TBAs (Details)

v3.7.0.1
Derivative Instruments and Hedging Activities Put and Call Options for TBAs (Details) - USD ($)
$ in Thousands
Mar. 31, 2017
Dec. 31, 2016
Mar. 31, 2016
Dec. 31, 2015
Derivative [Line Items]        
Derivative, Notional Amount $ 15,935,535 $ 18,802,500 $ 26,390,596 $ 21,998,381
Options Held [Member]        
Derivative [Line Items]        
Derivative, Notional Amount 1,770,000 1,136,000 $ 2,000,000 $ 0
Derivative Financial Instruments, Liabilities [Member]        
Derivative [Line Items]        
Derivative, Notional Amount 4,105,269 3,543,593    
Derivative, Fair Value, Net (20,363) (12,501)    
Derivative Financial Instruments, Liabilities [Member] | Options Held [Member]        
Derivative [Line Items]        
Derivative, Notional Amount 1,770,000 0    
Derivative, Fair Value, Net (7,003) 0    
Derivative Financial Instruments, Assets [Member]        
Derivative [Line Items]        
Derivative, Notional Amount 21,576,266 21,708,907    
Derivative, Fair Value, Net 253,564 324,182    
Derivative Financial Instruments, Assets [Member] | Options Held [Member]        
Derivative [Line Items]        
Derivative, Notional Amount 0 1,136,000    
Derivative, Fair Value, Net 0 42,633    
Long [Member] | Options Held [Member]        
Derivative [Line Items]        
Derivative, Notional Amount 4,300,000 2,500,000    
Short [Member] | Options Held [Member]        
Derivative [Line Items]        
Derivative, Notional Amount $ 2,530,000 $ 3,636,000