Annual report pursuant to Section 13 and 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
Dec. 31, 2011
Dec. 31, 2010
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale Securities $ 6,249,252 $ 1,354,405
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale Securities, Adjustable Rate 231,678 269,512
Available-for-sale Securities, Fixed Rate 4,821,479 746,957
Available-for-sale Securities 5,053,157 1,016,469
Mortgage-backed Securities, Issued by Private Enterprises [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale Securities, Adjustable Rate 995,014 245,517
Available-for-sale Securities, Fixed Rate 201,081 92,419
Available-for-sale Securities 1,196,095 337,936
Collateralized Mortgage Backed Securities [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale Securities, Adjustable Rate 1,226,692 515,029
Available-for-sale Securities, Fixed Rate 5,022,560 839,376
Available-for-sale Securities $ 6,249,252 $ 1,354,405