Annual report pursuant to Section 13 and 15(d)

Available-for-sale Securities Classified by Rate Type (Details)

v3.10.0.1
Available-for-sale Securities Classified by Rate Type (Details) - USD ($)
$ in Thousands
Dec. 31, 2018
Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]    
Adjustable Rate $ 3,494,244 $ 2,645,930
Fixed Rate 22,058,360 18,574,889
Available-for-sale securities, at fair value 25,552,604 21,220,819
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]    
Debt Securities, Available-for-sale [Line Items]    
Adjustable Rate 19,073 23,220
Fixed Rate 21,665,960 18,215,505
Available-for-sale securities, at fair value 21,685,033 18,238,725
Mortgage-backed Securities, Issued by Private Enterprises [Member]    
Debt Securities, Available-for-sale [Line Items]    
Adjustable Rate 3,475,171 2,622,710
Fixed Rate 392,400 359,384
Available-for-sale securities, at fair value $ 3,867,571 $ 2,982,094