Quarterly report pursuant to Section 13 or 15(d)

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

v3.4.0.3
Schedule of Derivative Instruments in Statement of Financial Position, Fair Value (Details) - USD ($)
$ in Thousands
Mar. 31, 2016
Dec. 31, 2015
Mar. 31, 2015
Dec. 31, 2014
Notional Disclosures [Abstract]        
Derivative, Notional Amount $ 26,390,596 $ 21,998,381 $ 33,709,043 $ 48,115,523
Inverse Interest-Only Securities [Member]        
Derivative, Fair Value, Net [Abstract]        
Derivative, Fair Value, Net 158,786 159,582    
Notional Disclosures [Abstract]        
Derivative, Notional Amount 882,726 932,037 1,106,210 1,168,226
Interest Rate Swap [Member]        
Notional Disclosures [Abstract]        
Derivative, Notional Amount 15,425,513 14,268,806 19,929,000 18,584,000
Credit Default Swap [Member]        
Notional Disclosures [Abstract]        
Derivative, Notional Amount 125,000 125,000 125,000 125,000
Interest Rate Swaption [Member]        
Notional Disclosures [Abstract]        
Derivative, Notional Amount 5,200,000 5,200,000 12,960,000 12,410,000
Forward Contracts [Member]        
Notional Disclosures [Abstract]        
Derivative, Notional Amount 1,637,000 297,000 2,496,000 1,325,000
Options Held [Member]        
Notional Disclosures [Abstract]        
Derivative, Notional Amount 2,000,000 0 2,500,000 2,000,000
Swap [Member]        
Notional Disclosures [Abstract]        
Derivative, Notional Amount     3,000,000 14,000,000
Total Return Swap [Member]        
Derivative, Fair Value, Net [Abstract]        
Derivative, Fair Value, Net (7,120) 1,645    
Notional Disclosures [Abstract]        
Derivative, Notional Amount 868,145 889,418 877,529 598,459
Loan Purchase Commitments [Member]        
Notional Disclosures [Abstract]        
Derivative, Notional Amount 252,212 286,120 $ 707,304 $ 554,838
Derivative Financial Instruments, Assets [Member]        
Derivative, Fair Value, Net [Abstract]        
Derivative, Fair Value, Net 197,847 271,509    
Notional Disclosures [Abstract]        
Derivative, Notional Amount 17,869,498 21,735,997    
Derivative Financial Instruments, Assets [Member] | Inverse Interest-Only Securities [Member]        
Notional Disclosures [Abstract]        
Derivative, Notional Amount 882,726 932,037    
Derivative Financial Instruments, Assets [Member] | Interest Rate Swap [Member]        
Derivative, Fair Value, Net [Abstract]        
Derivative, Fair Value, Net 18,162 91,757    
Notional Disclosures [Abstract]        
Derivative, Notional Amount 8,865,513 14,268,806    
Derivative Financial Instruments, Assets [Member] | Credit Default Swap [Member]        
Derivative, Fair Value, Net [Abstract]        
Derivative, Fair Value, Net 0 0    
Notional Disclosures [Abstract]        
Derivative, Notional Amount 0 0    
Derivative Financial Instruments, Assets [Member] | Interest Rate Swaption [Member]        
Derivative, Fair Value, Net [Abstract]        
Derivative, Fair Value, Net 10,482 17,374    
Notional Disclosures [Abstract]        
Derivative, Notional Amount 3,700,000 4,700,000    
Derivative Financial Instruments, Assets [Member] | Forward Contracts [Member]        
Derivative, Fair Value, Net [Abstract]        
Derivative, Fair Value, Net 9,557 1,074    
Notional Disclosures [Abstract]        
Derivative, Notional Amount 2,187,000 847,000    
Derivative Financial Instruments, Assets [Member] | Options Held [Member]        
Derivative, Fair Value, Net [Abstract]        
Derivative, Fair Value, Net 366      
Notional Disclosures [Abstract]        
Derivative, Notional Amount 2,000,000      
Derivative Financial Instruments, Assets [Member] | Total Return Swap [Member]        
Derivative, Fair Value, Net [Abstract]        
Derivative, Fair Value, Net 0 1,645    
Notional Disclosures [Abstract]        
Derivative, Notional Amount 0 889,418    
Derivative Financial Instruments, Assets [Member] | Loan Purchase Commitments [Member]        
Derivative, Fair Value, Net [Abstract]        
Derivative, Fair Value, Net 494 77    
Notional Disclosures [Abstract]        
Derivative, Notional Amount 234,259 98,736    
Derivative Financial Instruments, Liabilities [Member]        
Derivative, Fair Value, Net [Abstract]        
Derivative, Fair Value, Net (77,038) (7,285)    
Notional Disclosures [Abstract]        
Derivative, Notional Amount 9,621,098 1,362,384    
Derivative Financial Instruments, Liabilities [Member] | Inverse Interest-Only Securities [Member]        
Derivative, Fair Value, Net [Abstract]        
Derivative, Fair Value, Net 0 0    
Notional Disclosures [Abstract]        
Derivative, Notional Amount 0 0    
Derivative Financial Instruments, Liabilities [Member] | Interest Rate Swap [Member]        
Derivative, Fair Value, Net [Abstract]        
Derivative, Fair Value, Net (65,715) 0    
Notional Disclosures [Abstract]        
Derivative, Notional Amount 6,560,000 0    
Derivative Financial Instruments, Liabilities [Member] | Credit Default Swap [Member]        
Derivative, Fair Value, Net [Abstract]        
Derivative, Fair Value, Net (390) (703)    
Notional Disclosures [Abstract]        
Derivative, Notional Amount 125,000 125,000    
Derivative Financial Instruments, Liabilities [Member] | Interest Rate Swaption [Member]        
Derivative, Fair Value, Net [Abstract]        
Derivative, Fair Value, Net (473) (4,831)    
Notional Disclosures [Abstract]        
Derivative, Notional Amount 1,500,000 500,000    
Derivative Financial Instruments, Liabilities [Member] | Forward Contracts [Member]        
Derivative, Fair Value, Net [Abstract]        
Derivative, Fair Value, Net (3,328) (1,324)    
Notional Disclosures [Abstract]        
Derivative, Notional Amount 550,000 550,000    
Derivative Financial Instruments, Liabilities [Member] | Options Held [Member]        
Derivative, Fair Value, Net [Abstract]        
Derivative, Fair Value, Net 0      
Notional Disclosures [Abstract]        
Derivative, Notional Amount 0      
Derivative Financial Instruments, Liabilities [Member] | Total Return Swap [Member]        
Derivative, Fair Value, Net [Abstract]        
Derivative, Fair Value, Net (7,120) 0    
Notional Disclosures [Abstract]        
Derivative, Notional Amount 868,145 0    
Derivative Financial Instruments, Liabilities [Member] | Loan Purchase Commitments [Member]        
Derivative, Fair Value, Net [Abstract]        
Derivative, Fair Value, Net (12) (427)    
Notional Disclosures [Abstract]        
Derivative, Notional Amount $ 17,953 $ 187,384