Quarterly report pursuant to Section 13 or 15(d)

Derivative Instruments and Hedging Activities Schedule of Constant Maturity Swaps (Details)

v2.4.0.8
Derivative Instruments and Hedging Activities Schedule of Constant Maturity Swaps (Details) (USD $)
In Thousands, unless otherwise specified
Jun. 30, 2013
Dec. 31, 2012
Swap [Member]
   
Derivative [Line Items]    
Derivative, Notional Amount $ 19,000,000  
Derivative, Fair Value, Net (14,058)  
Derivative, Cost 0  
Derivative, Unrealized Gains (Losses) (14,058)  
Derivative, Average Strike Swap Rate 0.892%  
Derivative Financial Instruments, Assets [Member]
   
Derivative [Line Items]    
Derivative, Notional Amount 29,556,972 9,768,656
Derivative, Fair Value, Net 699,351 462,080
Derivative Financial Instruments, Assets [Member] | Swap [Member]
   
Derivative [Line Items]    
Derivative, Notional Amount 0  
Derivative, Fair Value, Net 0  
Determination Date, August 2013 [Member] | Swap [Member]
   
Derivative [Line Items]    
Derivative, Notional Amount 8,000,000  
Derivative, Fair Value, Net (3,497)  
Derivative, Cost 0  
Derivative, Unrealized Gains (Losses) (3,497)  
Derivative, Average Strike Swap Rate 0.837%  
Determination Date, September 2013 [Member] | Swap [Member]
   
Derivative [Line Items]    
Derivative, Notional Amount 5,000,000  
Derivative, Fair Value, Net (6,527)  
Derivative, Cost 0  
Derivative, Unrealized Gains (Losses) (6,527)  
Derivative, Average Strike Swap Rate 0.981%  
Determination Date, November 2013 [Member] | Swap [Member]
   
Derivative [Line Items]    
Derivative, Notional Amount 1,000,000  
Derivative, Fair Value, Net (670)  
Derivative, Cost 0  
Derivative, Unrealized Gains (Losses) (670)  
Derivative, Average Strike Swap Rate 0.90%  
Determination Date, December 2013 [Member] | Swap [Member]
   
Derivative [Line Items]    
Derivative, Notional Amount 5,000,000  
Derivative, Fair Value, Net (3,364)  
Derivative, Cost 0  
Derivative, Unrealized Gains (Losses) $ (3,364)  
Derivative, Average Strike Swap Rate 0.89%