Quarterly report pursuant to Section 13 or 15(d)

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

v3.7.0.1
Available-for-sale Securities Classified by Rate Type (Details) - USD ($)
$ in Thousands
Mar. 31, 2017
Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale Securities, Adjustable Rate $ 1,927,115 $ 1,605,313
Available-for-sale Securities, Fixed Rate 15,391,582 11,523,544
Available-for-sale Securities 17,318,697 13,128,857
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale Securities, Adjustable Rate 28,422 30,463
Available-for-sale Securities, Fixed Rate 15,091,463 11,196,011
Available-for-sale Securities 15,119,885 11,226,474
Mortgage-backed Securities, Issued by Private Enterprises [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale Securities, Adjustable Rate 1,898,693 1,574,850
Available-for-sale Securities, Fixed Rate 300,119 327,533
Available-for-sale Securities $ 2,198,812 $ 1,902,383