Annual report pursuant to Section 13 and 15(d)

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

v3.10.0.1
Derivative Instruments and Hedging Activities Put and Call Options for TBAs (Details) - USD ($)
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Derivative [Line Items]      
Notional $ 36,528,169,000 $ 31,226,878,000 $ 18,802,500,000
Derivative Financial Instruments, Assets [Member]      
Derivative [Line Items]      
Notional 36,258,904,000 25,503,371,000  
Fair Value 319,981,000 309,918,000  
Derivative Financial Instruments, Liabilities [Member]      
Derivative [Line Items]      
Notional 5,403,265,000 8,335,507,000  
Fair Value (820,590,000) (31,903,000)  
Options Held [Member] | Derivative Financial Instruments, Assets [Member]      
Derivative [Line Items]      
Notional 0    
Fair Value 0 0  
Options Held [Member] | Derivative Financial Instruments, Liabilities [Member]      
Derivative [Line Items]      
Notional 1,767,000,000    
Fair Value (25,296,000) 0  
Options Held [Member] | Long [Member]      
Derivative [Line Items]      
Notional 5,400,000,000 0  
Options Held [Member] | Short [Member]      
Derivative [Line Items]      
Notional $ 7,200,000,000 $ 0