Quarterly report pursuant to Section 13 or 15(d)

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

v3.3.0.814
Available-for-sale Securities Classified by Rate Type (Details) - USD ($)
$ in Thousands
Sep. 30, 2015
Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale Securities, Adjustable Rate $ 2,095,657 $ 2,687,117
Available-for-sale Securities, Fixed Rate 9,337,538 11,653,985
Available-for-sale securities, at fair value 11,433,195 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 114,929 128,285
Available-for-sale Securities, Fixed Rate 8,911,071 11,164,032
Available-for-sale securities, at fair value 9,026,000 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 1,980,728 2,558,832
Available-for-sale Securities, Fixed Rate 426,467 489,953
Available-for-sale securities, at fair value $ 2,407,195 $ 3,048,785