Quarterly report pursuant to Section 13 or 15(d)

Available-for-Sale Securities, at Fair Value (Details)

v3.4.0.3
Available-for-Sale Securities, at Fair Value (Details) - USD ($)
$ in Thousands
Mar. 31, 2016
Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale securities, at fair value $ 9,584,454 $ 7,825,320
Available-for-sale Securities Pledged as Collateral 9,456,721 7,767,074
Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale securities, at fair value 1,578,471 1,678,814
Federal National Mortgage Association Certificates and Obligations (FNMA) [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale securities, at fair value 6,177,794 3,602,348
Government National Mortgage Association Certificates and Obligations (GNMA) [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale securities, at fair value 252,831 691,728
Mortgage-backed Securities, Issued by Private Enterprises [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale securities, at fair value $ 1,575,358 $ 1,852,430