Annual report pursuant to Section 13 and 15(d)

Derivative Instruments and Hedging Activities Schedule of Derivative Instruments in Statement of Financial Position, Fair Value (Details)

v2.4.0.6
Derivative Instruments and Hedging Activities Schedule of Derivative Instruments in Statement of Financial Position, Fair Value (Details) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2011
Dec. 31, 2010
Derivative Financial Instruments, Assets [Member]
   
Derivatives, Fair Value [Line Items]    
Derivative Asset, Fair Value, Net $ 251,856 $ 38,109
Derivative Asset, Notional Amount 4,855,985 361,035
Derivative Financial Instruments, Liabilities [Member]
   
Derivatives, Fair Value [Line Items]    
Derivative Liability, Fair Value, Net (49,080) (158)
Derivative Liability, Notional Amount 6,814,812 850,000
Inverse Interest-Only Securities [Member] | Derivative Financial Instruments, Assets [Member]
   
Derivatives, Fair Value [Line Items]    
Derivative Asset, Fair Value, Net 157,421 30,944
Inverse Interest-Only Securities [Member] | Derivative Financial Instruments, Liabilities [Member]
   
Derivatives, Fair Value [Line Items]    
Derivative Liability, Fair Value, Net 0  
Derivative Liability, Notional Amount   0
Interest Rate Swap [Member] | Derivative Financial Instruments, Assets [Member]
   
Derivatives, Fair Value [Line Items]    
Derivative Asset, Fair Value, Net   0
Interest Rate Swaption [Member] | Derivative Financial Instruments, Assets [Member]
   
Derivatives, Fair Value [Line Items]    
Derivative Asset, Fair Value, Net   4,028
Interest Rate Swaption [Member] | Derivative Financial Instruments, Liabilities [Member]
   
Derivatives, Fair Value [Line Items]    
Derivative Liability, Fair Value, Net   0
Other Contract [Member] | Derivative Financial Instruments, Assets [Member]
   
Derivatives, Fair Value [Line Items]    
Derivative Asset, Fair Value, Net 2,664  
Forward Sale Commitment [Member] | Derivative Financial Instruments, Assets [Member]
   
Derivatives, Fair Value [Line Items]    
Derivative Asset, Fair Value, Net   $ 0