Quarterly report pursuant to Section 13 or 15(d)

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

v3.2.0.727
Available-for-sale Securities Classified by Rate Type (Details) - USD ($)
$ in Thousands
Jun. 30, 2015
Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale Securities, Adjustable Rate $ 2,351,219 $ 2,687,117
Available-for-sale Securities, Fixed Rate 10,456,439 11,653,985
Available-for-sale securities, at fair value 12,807,658 14,341,102
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale Securities, Adjustable Rate 119,710 128,285
Available-for-sale Securities, Fixed Rate 9,981,103 11,164,032
Available-for-sale securities, at fair value 10,100,813 11,292,317
Mortgage-backed Securities, Issued by Private Enterprises [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale Securities, Adjustable Rate 2,231,509 2,558,832
Available-for-sale Securities, Fixed Rate 475,336 489,953
Available-for-sale securities, at fair value $ 2,706,845 $ 3,048,785