Quarterly report pursuant to Section 13 or 15(d)

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

v3.21.1
Available-for-Sale Securities, at Fair Value (Details) - USD ($)
$ in Thousands
Mar. 31, 2021
Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]    
Available-for-sale securities, at fair value $ 11,473,390 $ 14,650,922
Available-for-sale securities, at fair value, pledged as collateral for borrowings 11,500,000 14,600,000
Federal National Mortgage Association Certificates and Obligations (FNMA) [Member]    
Debt Securities, Available-for-sale [Line Items]    
Available-for-sale securities, at fair value 8,604,120 11,486,658
Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member]    
Debt Securities, Available-for-sale [Line Items]    
Available-for-sale securities, at fair value 2,578,406 2,837,103
Government National Mortgage Association Certificates and Obligations (GNMA) [Member]    
Debt Securities, Available-for-sale [Line Items]    
Available-for-sale securities, at fair value 281,645 314,130
Mortgage-backed Securities, Issued by Private Enterprises [Member]    
Debt Securities, Available-for-sale [Line Items]    
Available-for-sale securities, at fair value $ 9,219 $ 13,031