Quarterly report pursuant to Section 13 or 15(d)

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

v2.4.0.8
Derivative Instruments and Hedging Activities Schedule of Derivative Instruments in Statement of Financial Position, Fair Value (Details) (USD $)
In Thousands, unless otherwise specified
Sep. 30, 2013
Dec. 31, 2012
Derivative Financial Instruments, Assets [Member]
   
Derivatives, Fair Value [Line Items]    
Derivative, Fair Value, Net $ 544,515 $ 462,080
Derivative, Notional Amount 27,657,236 9,768,656
Derivative Financial Instruments, Liabilities [Member]
   
Derivatives, Fair Value [Line Items]    
Derivative, Fair Value, Net (73,827) (129,294)
Derivative, Notional Amount 13,709,165 14,209,000
Inverse Interest-Only Securities [Member] | Derivative Financial Instruments, Assets [Member]
   
Derivatives, Fair Value [Line Items]    
Derivative, Fair Value, Net 226,744 304,975
Derivative, Notional Amount 1,648,236 1,909,351
Inverse Interest-Only Securities [Member] | Derivative Financial Instruments, Liabilities [Member]
   
Derivatives, Fair Value [Line Items]    
Derivative, Fair Value, Net 0 0
Derivative, Notional Amount 0 0
Interest Rate Swap [Member] | Derivative Financial Instruments, Assets [Member]
   
Derivatives, Fair Value [Line Items]    
Derivative, Fair Value, Net 51,374 0
Derivative, Notional Amount 17,575,000 0
Interest Rate Swap [Member] | Derivative Financial Instruments, Liabilities [Member]
   
Derivatives, Fair Value [Line Items]    
Derivative, Fair Value, Net 0 (129,055)
Derivative, Notional Amount 0 14,070,000
Credit Default Swap [Member] | Derivative Financial Instruments, Assets [Member]
   
Derivatives, Fair Value [Line Items]    
Derivative, Fair Value, Net 0 52,906
Derivative, Notional Amount 0 438,440
Credit Default Swap [Member] | Derivative Financial Instruments, Liabilities [Member]
   
Derivatives, Fair Value [Line Items]    
Derivative, Fair Value, Net (29,852) 0
Derivative, Notional Amount 1,462,165 0
Interest Rate Swaption [Member] | Derivative Financial Instruments, Assets [Member]
   
Derivatives, Fair Value [Line Items]    
Derivative, Fair Value, Net 237,871 102,048
Derivative, Notional Amount 4,430,000 4,950,000
Interest Rate Swaption [Member] | Derivative Financial Instruments, Liabilities [Member]
   
Derivatives, Fair Value [Line Items]    
Derivative, Fair Value, Net 0 0
Derivative, Notional Amount 0 0
Forward Contracts [Member]
   
Derivatives, Fair Value [Line Items]    
Derivative, Notional Amount 857,000 953,000
Forward Contracts [Member] | Derivative Financial Instruments, Assets [Member]
   
Derivatives, Fair Value [Line Items]    
Derivative, Fair Value, Net 21,896 1,917
Derivative, Notional Amount 1,504,000 2,414,000
Forward Contracts [Member] | Derivative Financial Instruments, Liabilities [Member]
   
Derivatives, Fair Value [Line Items]    
Derivative, Fair Value, Net (34,634) (239)
Derivative, Notional Amount 4,247,000 139,000
Options Held [Member] | Derivative Financial Instruments, Assets [Member]
   
Derivatives, Fair Value [Line Items]    
Derivative, Fair Value, Net 6,630  
Derivative, Notional Amount 2,500,000  
Options Held [Member] | Derivative Financial Instruments, Liabilities [Member]
   
Derivatives, Fair Value [Line Items]    
Derivative, Fair Value, Net 0  
Derivative, Notional Amount 0  
Swap [Member]
   
Derivatives, Fair Value [Line Items]    
Derivative, Fair Value, Net (9,341)  
Derivative, Notional Amount 8,000,000  
Swap [Member] | Derivative Financial Instruments, Assets [Member]
   
Derivatives, Fair Value [Line Items]    
Derivative, Fair Value, Net 0  
Derivative, Notional Amount 0  
Swap [Member] | Derivative Financial Instruments, Liabilities [Member]
   
Derivatives, Fair Value [Line Items]    
Derivative, Fair Value, Net (9,341)  
Derivative, Notional Amount 8,000,000  
Forward Purchase Commitment [Member] | Derivative Financial Instruments, Assets [Member]
   
Derivatives, Fair Value [Line Items]    
Derivative, Fair Value, Net   234
Derivative, Notional Amount   56,865
Forward Purchase Commitment [Member] | Derivative Financial Instruments, Liabilities [Member]
   
Derivatives, Fair Value [Line Items]    
Derivative, Fair Value, Net   0
Derivative, Notional Amount   $ 0