Quarterly report pursuant to Section 13 or 15(d)

Derivative Instruments and Hedging Activities Schedule of Credit Default Swaps, Receive Protection (Details)

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Derivative Instruments and Hedging Activities Schedule of Credit Default Swaps, Receive Protection (Details) (Credit Default Swap, Buying Protection [Member], USD $)
In Thousands, unless otherwise specified
 6 Months Ended 12 Months Ended
Jun. 30, 2013
Dec. 31, 2012
Derivative [Line Items]    
Derivative, Average Implied Credit Spread 247.81 254.06
Derivative, Notional Amount $ (1,630,404) $ (438,440)
Derivative, Fair Value, Net (8,198) 52,906
Derivative, Cost (15,155) (81,788)
Derivative, Unrealized Gains (Losses) (23,353) (28,882)
Maturity Date, 09/20/2013 [Member]
    
Derivative [Line Items]    
Derivative, Maturity Date Sep. 20, 2013 Sep. 20, 2013
Derivative, Average Implied Credit Spread 460.00 460.00
Derivative, Notional Amount (45,000) (45,000)
Derivative, Fair Value, Net (91) (264)
Derivative, Cost (3,127) (3,127)
Derivative, Unrealized Gains (Losses) (3,218) (3,391)
Maturity Date, 12/20/2013 [Member]
    
Derivative [Line Items]    
Derivative, Maturity Date Dec. 20, 2013 Dec. 20, 2013
Derivative, Average Implied Credit Spread 181.91 181.91
Derivative, Notional Amount (105,000) (105,000)
Derivative, Fair Value, Net (116) (198)
Derivative, Cost (3,225) (3,225)
Derivative, Unrealized Gains (Losses) (3,341) (3,423)
Maturity Date, 06/20/2016 [Member]
    
Derivative [Line Items]    
Derivative, Maturity Date Jun. 20, 2016 Jun. 20, 2016
Derivative, Average Implied Credit Spread 105.50 105.50
Derivative, Notional Amount (100,000) (100,000)
Derivative, Fair Value, Net (1,722) (1,940)
Derivative, Cost (260) (260)
Derivative, Unrealized Gains (Losses) (1,982) (2,200)
Maturity Date, 12/20/2016 [Member]
    
Derivative [Line Items]    
Derivative, Maturity Date Dec. 20, 2016 Dec. 20, 2016
Derivative, Average Implied Credit Spread 496.00 496.00
Derivative, Notional Amount (25,000) (25,000)
Derivative, Fair Value, Net 245 527
Derivative, Cost (4,062) (4,062)
Derivative, Unrealized Gains (Losses) (3,817) (3,535)
Maturity Date, 6/20/2018 [Member]
    
Derivative [Line Items]    
Derivative, Maturity Date Jun. 20, 2018  
Derivative, Average Implied Credit Spread 247.35  
Derivative, Notional Amount (1,300,000)  
Derivative, Fair Value, Net (22,858)  
Derivative, Cost 21,277  
Derivative, Unrealized Gains (Losses) (1,581)  
Maturity Date, 05/25/2046 [Member]
    
Derivative [Line Items]    
Derivative, Maturity Date May 25, 2046 May 25, 2046
Derivative, Average Implied Credit Spread 356.00 297.60
Derivative, Notional Amount (55,404) (163,440)
Derivative, Fair Value, Net 16,344 54,781
Derivative, Cost (25,758) (71,114)
Derivative, Unrealized Gains (Losses) $ (9,414) $ (16,333)