Quarterly report pursuant to Section 13 or 15(d)

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

v3.19.2
Available-for-Sale Securities, at Fair Value (Details) - USD ($)
$ in Thousands
Jun. 30, 2019
Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]    
Available-for-sale securities, at fair value $ 30,186,079 $ 25,552,604
Available-for-sale securities, at fair value, pledged as collateral for borrowings 28,800,000 25,200,000
Federal National Mortgage Association Certificates and Obligations (FNMA) [Member]    
Debt Securities, Available-for-sale [Line Items]    
Available-for-sale securities, at fair value 18,588,591 15,812,696
Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member]    
Debt Securities, Available-for-sale [Line Items]    
Available-for-sale securities, at fair value 7,034,641 4,930,963
Government National Mortgage Association Certificates and Obligations (GNMA) [Member]    
Debt Securities, Available-for-sale [Line Items]    
Available-for-sale securities, at fair value 685,211 941,374
Mortgage-backed Securities, Issued by Private Enterprises [Member]    
Debt Securities, Available-for-sale [Line Items]    
Available-for-sale securities, at fair value $ 3,877,636 $ 3,867,571