Quarterly report pursuant to Section 13 or 15(d)

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

v3.19.1
Derivative Instruments and Hedging Activities Schedule of Total Return Swaps (Details) - USD ($)
Mar. 31, 2019
Dec. 31, 2018
Mar. 31, 2018
Dec. 31, 2017
Derivative [Line Items]        
Notional $ 58,777,783,000 $ 36,528,169,000 $ 18,429,288,000 $ 31,226,878,000
Markit IOS Total Return Swap [Member]        
Derivative [Line Items]        
Notional 47,073,000 48,265,000    
Fair Value (231,000) (383,000)    
Cost Basis (59,000) (59,000)    
Derivative, Unrealized Gains (Losses) (172,000) (324,000)    
Markit IOS Total Return Swap [Member] | Maturity Date, 1/12/2043 [Member]        
Derivative [Line Items]        
Notional 20,877,000 21,395,000    
Fair Value (101,000) (153,000)    
Cost Basis (30,000) (30,000)    
Derivative, Unrealized Gains (Losses) (71,000) (123,000)    
Markit IOS Total Return Swap [Member] | Maturity Date, 1/12/2044 [Member]        
Derivative [Line Items]        
Notional 26,196,000 26,870,000    
Fair Value (130,000) (230,000)    
Cost Basis (29,000) (29,000)    
Derivative, Unrealized Gains (Losses) $ (101,000) $ (201,000)