Annual report pursuant to Section 13 and 15(d)

Derivative Instruments and Hedging Activities Components of Other Income (Expense) Related to Interest Rate and Credit Default Swaps (Details)

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Derivative Instruments and Hedging Activities Components of Other Income (Expense) Related to Interest Rate and Credit Default Swaps (Details) (USD $)
In Thousands, unless otherwise specified
 12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Derivative Instruments, Gain (Loss) [Line Items]      
Interest Expense on Interest Rate Swap and Swaption Agreements $ (38,448) $ (24,883)  
Termination of Interest Rate Swaps and Swaptions, Number of Positions 26 32  
Termination of Interest Rate Swaps and Swaptions, Notional Amount 4,450,000 3,200,000  
Termination of Interest Rate Swaps and Swaptions, Interest Spread Settlement (1,573) (5,952)  
Loss on Termination of Interest Rate Swaps and Swaptions (29,579) (16,970) (4,446)
Termination of Credit Default Swaps, Number of Positions 18 3  
Termination of Credit Default Swaps, Notional Amount 825,000 175,000  
Termination of Credit Default Swaps, Interest Spread Settlement (2,902) (1,131)  
Loss on Termination of Credit Default Swaps (17,570) 4,567  
Interest Rate Swap [Member]
      
Derivative Instruments, Gain (Loss) [Line Items]      
Derivative Liability, Average Notional Amount $ 9,891,749 $ 3,667,493