Annual report pursuant to Section 13 and 15(d)

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

v3.3.1.900
Derivative Instruments and Hedging Activities Schedule of Constant Maturity Swaps (Details) - USD ($)
$ in Thousands
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Derivative [Line Items]      
Derivative, Notional Amount $ 21,998,381 $ 48,115,523 $ 37,366,610
Swap [Member]      
Derivative [Line Items]      
Derivative, Average Strike Swap Rate   0.548%  
Derivative, Notional Amount $ 0 $ 14,000,000 $ 10,000,000
Derivative, Fair Value, Net   1,530  
Derivative, Cost   0  
Derivative, Unrealized Gains (Losses)   $ 1,530  
Swap [Member] | Determination Date, January 2015 [Member]      
Derivative [Line Items]      
Derivative, Average Strike Swap Rate   0.538%  
Derivative, Notional Amount   $ 7,000,000  
Derivative, Fair Value, Net   1,502  
Derivative, Cost   0  
Derivative, Unrealized Gains (Losses)   $ 1,502  
Swap [Member] | Determination Date, February 2015 [Member]      
Derivative [Line Items]      
Derivative, Average Strike Swap Rate   0.572%  
Derivative, Notional Amount   $ 2,000,000  
Derivative, Fair Value, Net   (13)  
Derivative, Cost   0  
Derivative, Unrealized Gains (Losses)   $ (13)  
Swap [Member] | Determination Date, March 2015 [Member]      
Derivative [Line Items]      
Derivative, Average Strike Swap Rate   0.552%  
Derivative, Notional Amount   $ 5,000,000  
Derivative, Fair Value, Net   41  
Derivative, Cost   0  
Derivative, Unrealized Gains (Losses)   $ 41