Annual report pursuant to Section 13 and 15(d)

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

v3.6.0.2
Available-for-Sale Securities, at Fair Value (Details) - USD ($)
$ in Thousands
Dec. 31, 2016
Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale securities, at fair value $ 13,128,857 $ 7,825,320
Available-for-sale Securities Pledged as Collateral 13,117,329 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 2,742,630 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 8,274,507 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 209,337 691,728
Mortgage-backed Securities, Issued by Private Enterprises [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale securities, at fair value $ 1,902,383 $ 1,852,430