Annual report pursuant to Section 13 and 15(d)

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

v3.20.4
Available-for-Sale Securities, at Fair Value (Details) - USD ($)
$ in Thousands
Dec. 31, 2020
Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]    
Available-for-sale securities, at fair value $ 14,650,922 $ 31,406,328
Available-for-sale securities, at fair value, pledged as collateral for borrowings 14,600,000 29,800,000
Federal National Mortgage Association Certificates and Obligations (FNMA) [Member]    
Debt Securities, Available-for-sale [Line Items]    
Available-for-sale securities, at fair value 11,486,658 21,252,575
Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member]    
Debt Securities, Available-for-sale [Line Items]    
Available-for-sale securities, at fair value 2,837,103 6,070,500
Government National Mortgage Association Certificates and Obligations (GNMA) [Member]    
Debt Securities, Available-for-sale [Line Items]    
Available-for-sale securities, at fair value 314,130 454,980
Mortgage-backed Securities, Issued by Private Enterprises [Member]    
Debt Securities, Available-for-sale [Line Items]    
Available-for-sale securities, at fair value $ 13,031 $ 3,628,273