Quarterly report pursuant to Section 13 or 15(d)

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

v3.10.0.1
Available-for-Sale Securities, Weighted Average Life Classifications (Details) - USD ($)
$ in Thousands
Jun. 30, 2018
Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]    
Less than or equal to 1 year $ 89,887  
Greater than 1 year and less than or equal to 3 years 149,082  
Greater than 3 years and less than or equal to 5 years 686,166  
Greater than 5 years and less than or equal to 10 years 14,308,522  
Greater than 10 years 4,059,697  
Available-for-sale securities, at fair value 19,293,354 $ 21,220,819
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]    
Debt Securities, Available-for-sale [Line Items]    
Less than or equal to 1 year 7,054  
Greater than 1 year and less than or equal to 3 years 39,666  
Greater than 3 years and less than or equal to 5 years 275,305  
Greater than 5 years and less than or equal to 10 years 12,156,899  
Greater than 10 years 3,310,067  
Available-for-sale securities, at fair value 15,788,991 18,238,725
Mortgage-backed Securities, Issued by Private Enterprises [Member]    
Debt Securities, Available-for-sale [Line Items]    
Less than or equal to 1 year 82,833  
Greater than 1 year and less than or equal to 3 years 109,416  
Greater than 3 years and less than or equal to 5 years 410,861  
Greater than 5 years and less than or equal to 10 years 2,151,623  
Greater than 10 years 749,630  
Available-for-sale securities, at fair value $ 3,504,363 $ 2,982,094