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, 2012
Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale securities, at fair value $ 13,666,954 $ 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 188,429 231,678
Available-for-sale Securities, Fixed Rate 10,823,674 4,821,479
Available-for-sale securities, at fair value 11,012,103 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 2,334,950 995,014
Available-for-sale Securities, Fixed Rate 319,901 201,081
Available-for-sale securities, at fair value 2,654,851 1,196,095
Collateralized Mortgage Backed Securities [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale Securities, Adjustable Rate 2,523,379 1,226,692
Available-for-sale Securities, Fixed Rate 11,143,575 5,022,560
Available-for-sale securities, at fair value $ 13,666,954 $ 6,249,252