Annual report pursuant to Section 13 and 15(d)

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

v3.20.4
Derivative Instruments and Hedging Activities Schedule of Total Return Swaps (Details) - USD ($)
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Derivative [Line Items]      
Notional $ 23,932,603,000 $ 48,445,497,000 $ 36,528,169,000
Markit IOS Total Return Swap [Member]      
Derivative [Line Items]      
Notional   41,890,000  
Fair Value   (29,000)  
Cost Basis   (59,000)  
Derivative, Unrealized Gains (Losses)   30,000  
Markit IOS Total Return Swap [Member] | Maturity Date, 1/12/2043 [Member]      
Derivative [Line Items]      
Notional   18,625,000  
Fair Value   5,000  
Cost Basis   (30,000)  
Derivative, Unrealized Gains (Losses)   35,000  
Markit IOS Total Return Swap [Member] | Maturity Date, 1/12/2044 [Member]      
Derivative [Line Items]      
Notional   23,265,000  
Fair Value   (34,000)  
Cost Basis   (29,000)  
Derivative, Unrealized Gains (Losses)   $ (5,000)