Quarterly report pursuant to Section 13 or 15(d)

Trading Securities, at Fair Value (Details)

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Trading Securities, at Fair Value (Details) (USD $)
In Thousands, unless otherwise specified
6 Months Ended
Jun. 30, 2013
Dec. 31, 2012
Schedule of Trading Securities and Other Trading Assets [Line Items]    
Trading Securities, Cost $ 997,682  
Trading securities, at fair value 1,001,172 1,002,062
Trading Securities, Gross Unrealized Gain (Loss) 3,490 5,048
Trading Securities, Change in Unrealized Holding Gain (Loss) (1,558)  
Assets Sold under Agreements to Repurchase, Market Value 16,495,493 14,287,224
US Treasury Securities [Member]
   
Schedule of Trading Securities and Other Trading Assets [Line Items]    
Assets Sold under Agreements to Repurchase, Market Value $ 1,001,172 $ 1,002,062