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) (USD $)
In Thousands, unless otherwise specified
3 Months Ended 12 Months Ended 3 Months Ended 12 Months Ended 3 Months Ended 12 Months Ended 3 Months Ended 12 Months Ended 3 Months Ended 12 Months Ended 3 Months Ended 12 Months Ended
Mar. 31, 2012
Mar. 31, 2011
Mar. 31, 2012
Credit Default Swap, Buying Protection [Member]
Dec. 31, 2011
Credit Default Swap, Buying Protection [Member]
Mar. 31, 2012
Maturity Date, 09/20/2013 [Member]
Credit Default Swap, Buying Protection [Member]
Dec. 31, 2011
Maturity Date, 09/20/2013 [Member]
Credit Default Swap, Buying Protection [Member]
Mar. 31, 2012
Maturity Date, 12/20/2013 [Member]
Credit Default Swap, Buying Protection [Member]
Dec. 31, 2011
Maturity Date, 12/20/2013 [Member]
Credit Default Swap, Buying Protection [Member]
Mar. 31, 2012
Maturity Date, 06/20/2016 [Member]
Credit Default Swap, Buying Protection [Member]
Dec. 31, 2011
Maturity Date, 06/20/2016 [Member]
Credit Default Swap, Buying Protection [Member]
Mar. 31, 2012
Maturity Date, 12/20/2016 [Member]
Credit Default Swap, Buying Protection [Member]
Dec. 31, 2011
Maturity Date, 12/20/2016 [Member]
Credit Default Swap, Buying Protection [Member]
Mar. 31, 2012
Maturity Date, 05/25/2046 [Member]
Credit Default Swap, Buying Protection [Member]
Dec. 31, 2011
Maturity Date, 05/25/2046 [Member]
Credit Default Swap, Buying Protection [Member]
Derivative [Line Items]                            
Derivative, Maturity Date         Sep. 20, 2013 Sep. 20, 2013 Dec. 20, 2013 Dec. 20, 2013 Jun. 20, 2016 Jun. 20, 2016 Dec. 20, 2016 Dec. 20, 2016 May 25, 2046 May 25, 2046
Derivative, Average Basis Spread on Variable Rate     33976.00% 34194.00% 46000.00% 46000.00% 18190.00% 17250.00% 10500.00% 10500.00% 68322.00% 68438.00% 37723.00% 37723.00%
Notional Amount of Derivatives     $ (541,426) $ (544,699) $ (45,000) $ (45,000) $ (105,000) $ (105,000) $ (150,000) $ (150,000) $ (122,000) $ (125,000) $ (119,426) $ (119,699)
Derivative, Fair Value, Net     62,924 86,136 277 2,422 1,312 3,742 (2,480) 2,074 3,556 10,200 60,259 67,698
Derivative, Cost     (77,091) (77,091) (3,127) (3,127) (3,225) (3,225) (355) (355) (13,062) (13,062) (57,322) (57,322)
Derivative, Gain (Loss) on Derivative, Net $ (8,890) $ 5,347 $ (14,167) $ 9,045 $ (2,850) $ (705) $ (1,913) $ 517 $ (2,835) $ 1,719 $ (9,506) $ (2,862) $ 2,937 $ 10,376