Quarterly report pursuant to Section 13 or 15(d)

Available-for-Sale Securities, Weighted Average Life Classifications (Details)

v3.8.0.1
Available-for-Sale Securities, Weighted Average Life Classifications (Details) - USD ($)
$ in Thousands
Sep. 30, 2017
Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]    
Less than or equal to 1 year $ 180,692  
Greater than 1 year and less than or equal to 3 years 287,577  
Greater than 3 years and less than or equal to 5 years 1,628,250  
Greater than 5 years and less than or equal to 10 years 17,328,678  
Greater than 10 years 773,897  
Available-for-sale securities, at fair value 20,199,094 $ 13,128,857
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Less than or equal to 1 year 15,632  
Greater than 1 year and less than or equal to 3 years 38,357  
Greater than 3 years and less than or equal to 5 years 1,192,719  
Greater than 5 years and less than or equal to 10 years 16,285,575  
Greater than 10 years 22,088  
Available-for-sale securities, at fair value 17,554,371 11,226,474
Mortgage-backed Securities, Issued by Private Enterprises [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Less than or equal to 1 year 165,060  
Greater than 1 year and less than or equal to 3 years 249,220  
Greater than 3 years and less than or equal to 5 years 435,531  
Greater than 5 years and less than or equal to 10 years 1,043,103  
Greater than 10 years 751,809  
Available-for-sale securities, at fair value $ 2,644,723 $ 1,902,383