Quarterly report pursuant to Section 13 or 15(d)

Derivative Instruments and Hedging Activities Schedule of Total Return Swaps (Details)

v3.3.0.814
Derivative Instruments and Hedging Activities Schedule of Total Return Swaps (Details) - USD ($)
$ in Thousands
Sep. 30, 2015
Jun. 30, 2015
Dec. 31, 2014
Sep. 30, 2014
Jun. 30, 2014
Dec. 31, 2013
Derivative [Line Items]            
Derivative, Notional Amount $ (28,317,580) $ (27,401,335) $ (48,115,523) $ (57,015,981) $ (43,379,217) $ (37,366,610)
Total Return Swap [Member]            
Derivative [Line Items]            
Derivative, Notional Amount (887,964)   (598,459)      
Derivative, Fair Value, Net (4,992)   1,387      
Derivative, Cost (1,763)   (1,732)      
Derivative, Unrealized Gains (Losses) (6,755)   (345)      
Maturity Date, 1/12/2043 [Member] | Total Return Swap [Member]            
Derivative [Line Items]            
Derivative, Notional Amount (378,890)   (411,281)      
Derivative, Fair Value, Net (1,808)   763      
Derivative, Cost (866)   (1,457)      
Derivative, Unrealized Gains (Losses) (2,674)   (694)      
Maturity Date, 1/12/2044 [Member] | Total Return Swap [Member]            
Derivative [Line Items]            
Derivative, Notional Amount (332,924)   (187,178)      
Derivative, Fair Value, Net (1,589)   624      
Derivative, Cost (1,679)   (275)      
Derivative, Unrealized Gains (Losses) (3,268)   349      
Maturity Date, 1/12/2045 [Member] | Total Return Swap [Member]            
Derivative [Line Items]            
Derivative, Notional Amount (176,150)          
Derivative, Fair Value, Net (1,595)          
Derivative, Cost 782          
Derivative, Unrealized Gains (Losses) (813)          
Derivative Financial Instruments, Assets [Member]            
Derivative [Line Items]            
Derivative, Notional Amount (18,899,975)   (36,315,523)      
Derivative, Fair Value, Net $ 296,731   $ 380,791