Annual report pursuant to Section 13 and 15(d)

Derivative Instruments and Hedging Activities Schedule of Interest Rate Swaps Associated with U.S. Treasuries (Details)

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Derivative Instruments and Hedging Activities Schedule of Interest Rate Swaps Associated with U.S. Treasuries (Details) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2013
Dec. 31, 2012
Derivative [Line Items]    
Trading securities, at fair value $ 1,000,180 $ 1,002,062
Interest Rate Swaps Associated with U.S. Treasuries [Member]
   
Derivative [Line Items]    
Derivative, Notional Amount 1,000,000 1,000,000
Interest Rate Swaps Associated with U.S. Treasuries [Member] | Derivative Maturity Over Two And Within Three Years From Balance Sheet Date [Member]
   
Derivative [Line Items]    
Derivative, Notional Amount $ 1,000,000 $ 1,000,000
Derivative, Average Fixed Interest Rate 0.955% 0.799%
Derivative, Average Variable Interest Rate 0.239% 0.35%
Derivative, Weighted Average Remaining Maturity 2.667 2.278