Quarterly report pursuant to Section 13 or 15(d)

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

v3.2.0.727
Derivative Instruments and Hedging Activities Schedule of Total Return Swaps (Details) - Position [Domain] - USD ($)
$ in Thousands
Jun. 30, 2015
Mar. 31, 2015
Dec. 31, 2014
Jun. 30, 2014
Mar. 31, 2014
Dec. 31, 2013
Derivative [Line Items]            
Derivative, Notional Amount $ (27,401,335) $ (33,709,043) $ (48,115,523) $ (43,379,217) $ (43,576,146) $ (37,366,610)
Derivative Financial Instruments, Assets [Member]            
Derivative [Line Items]            
Derivative, Notional Amount (26,416,319)   (36,315,523)      
Derivative, Fair Value, Net 347,322   380,791      
Derivative Financial Instruments, Assets [Member] | Total Return Swap [Member]            
Derivative [Line Items]            
Derivative, Notional Amount (988,409)   (598,459)      
Derivative, Fair Value, Net 591   1,387      
Derivative, Cost (8,665)   (1,732)      
Derivative, Unrealized Gains (Losses) (8,074)   (345)      
Derivative Financial Instruments, Assets [Member] | Maturity Date, 1/12/2043 [Member] | Total Return Swap [Member]            
Derivative [Line Items]            
Derivative, Notional Amount (390,645)   (411,281)      
Derivative, Fair Value, Net 641   763      
Derivative, Cost (866)   (1,457)      
Derivative, Unrealized Gains (Losses) (225)   (694)      
Derivative Financial Instruments, Assets [Member] | Maturity Date, 1/12/2044 [Member] | Total Return Swap [Member]            
Derivative [Line Items]            
Derivative, Notional Amount (597,764)   (187,178)      
Derivative, Fair Value, Net (50)   624      
Derivative, Cost (7,799)   (275)      
Derivative, Unrealized Gains (Losses) $ (7,849)   $ 349