Quarterly report pursuant to Section 13 or 15(d)

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

v2.4.0.6
Available-for-sale Securities Classified by Rate Type (Details) (USD $)
In Thousands, unless otherwise specified
Jun. 30, 2012
Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale securities, at fair value $ 10,724,149 $ 6,249,252
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale Securities, Adjustable Rate 221,568 231,678
Available-for-sale Securities, Fixed Rate 8,490,634 4,821,479
Available-for-sale securities, at fair value 8,712,202 5,053,157
Mortgage-backed Securities, Issued by Private Enterprises [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale Securities, Adjustable Rate 1,750,513 995,014
Available-for-sale Securities, Fixed Rate 261,434 201,081
Available-for-sale securities, at fair value 2,011,947 1,196,095
Collateralized Mortgage Backed Securities [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale Securities, Adjustable Rate 1,972,081 1,226,692
Available-for-sale Securities, Fixed Rate 8,752,068 5,022,560
Available-for-sale securities, at fair value $ 10,724,149 $ 6,249,252