Quarterly report pursuant to Section 13 or 15(d)

Schedule of Derivative Instruments in Statement of Financial Position, Fair Value (Details)

v3.10.0.1
Schedule of Derivative Instruments in Statement of Financial Position, Fair Value (Details) - USD ($)
Sep. 30, 2018
Jun. 30, 2018
Dec. 31, 2017
Sep. 30, 2017
Jun. 30, 2017
Dec. 31, 2016
Notional Disclosures [Abstract]            
Notional $ 41,330,283,000 $ 28,618,861,000 $ 31,226,878,000 $ 24,113,321,000 $ 16,988,116,000 $ 18,802,500,000
Inverse Interest-Only Securities [Member]            
Derivative, Fair Value, Net [Abstract]            
Fair Value 67,665,000   91,827,000      
Notional Disclosures [Abstract]            
Notional 498,826,000   588,246,000      
Total Return Swap [Member]            
Derivative, Fair Value, Net [Abstract]            
Fair Value 2,000   (106,000)      
Notional Disclosures [Abstract]            
Notional 49,691,000   63,507,000      
Derivative Financial Instruments, Assets [Member]            
Derivative, Fair Value, Net [Abstract]            
Fair Value 403,231,000   309,918,000      
Notional Disclosures [Abstract]            
Notional 33,229,283,000   25,503,371,000      
Derivative Financial Instruments, Assets [Member] | Inverse Interest-Only Securities [Member]            
Notional Disclosures [Abstract]            
Notional 498,826,000   588,246,000      
Derivative Financial Instruments, Assets [Member] | Interest Rate Swap [Member]            
Derivative, Fair Value, Net [Abstract]            
Fair Value 238,116,000   206,773,000      
Notional Disclosures [Abstract]            
Notional 28,128,766,000   21,516,125,000      
Derivative Financial Instruments, Assets [Member] | Interest Rate Swaption [Member]            
Derivative, Fair Value, Net [Abstract]            
Fair Value 24,912,000   10,405,000      
Notional Disclosures [Abstract]            
Notional 164,000,000   2,666,000,000      
Derivative Financial Instruments, Assets [Member] | Interest Rate Cap [Member]            
Derivative, Fair Value, Net [Abstract]            
Fair Value 52,370,000          
Notional Disclosures [Abstract]            
Notional 2,500,000,000          
Derivative Financial Instruments, Assets [Member] | Forward Contracts [Member]            
Derivative, Fair Value, Net [Abstract]            
Fair Value 15,212,000   913,000      
Notional Disclosures [Abstract]            
Notional 1,108,000,000   733,000,000      
Derivative Financial Instruments, Assets [Member] | Options Held [Member]            
Derivative, Fair Value, Net [Abstract]            
Fair Value 4,954,000   0      
Notional Disclosures [Abstract]            
Notional 780,000,000          
Derivative Financial Instruments, Assets [Member] | Total Return Swap [Member]            
Derivative, Fair Value, Net [Abstract]            
Fair Value 2,000   0      
Notional Disclosures [Abstract]            
Notional 49,691,000   0      
Derivative Financial Instruments, Assets [Member] | Short US Treasury Securities [Member]            
Derivative, Fair Value, Net [Abstract]            
Fair Value 0          
Notional Disclosures [Abstract]            
Notional 0          
Derivative Financial Instruments, Liabilities [Member]            
Derivative, Fair Value, Net [Abstract]            
Fair Value (797,504,000)   (31,903,000)      
Notional Disclosures [Abstract]            
Notional 11,521,000,000   8,335,507,000      
Derivative Financial Instruments, Liabilities [Member] | Inverse Interest-Only Securities [Member]            
Derivative, Fair Value, Net [Abstract]            
Fair Value 0   0      
Notional Disclosures [Abstract]            
Notional 0   0      
Derivative Financial Instruments, Liabilities [Member] | Interest Rate Swap [Member]            
Derivative, Fair Value, Net [Abstract]            
Fair Value 0   (29,867,000)      
Notional Disclosures [Abstract]            
Notional 2,375,000,000   6,966,000,000      
Derivative Financial Instruments, Liabilities [Member] | Interest Rate Swaption [Member]            
Derivative, Fair Value, Net [Abstract]            
Fair Value 0   0      
Notional Disclosures [Abstract]            
Notional 0   0      
Derivative Financial Instruments, Liabilities [Member] | Interest Rate Cap [Member]            
Derivative, Fair Value, Net [Abstract]            
Fair Value 0          
Notional Disclosures [Abstract]            
Notional 0          
Derivative Financial Instruments, Liabilities [Member] | Forward Contracts [Member]            
Derivative, Fair Value, Net [Abstract]            
Fair Value (43,314,000)   (1,930,000)      
Notional Disclosures [Abstract]            
Notional 8,216,000,000   1,306,000,000      
Derivative Financial Instruments, Liabilities [Member] | Options Held [Member]            
Derivative, Fair Value, Net [Abstract]            
Fair Value (1,329,000)   0      
Notional Disclosures [Abstract]            
Notional 130,000,000          
Derivative Financial Instruments, Liabilities [Member] | Total Return Swap [Member]            
Derivative, Fair Value, Net [Abstract]            
Fair Value 0   (106,000)      
Notional Disclosures [Abstract]            
Notional 0   63,507,000      
Derivative Financial Instruments, Liabilities [Member] | Short US Treasury Securities [Member]            
Derivative, Fair Value, Net [Abstract]            
Fair Value $ (752,861,000)   $ 0