Quarterly report pursuant to Section 13 or 15(d)

Derivative Instruments and Hedging Activities Short U.S. Treasury Securities (Details)

v3.19.2
Derivative Instruments and Hedging Activities Short U.S. Treasury Securities (Details) - USD ($)
Jun. 30, 2019
Mar. 31, 2019
Dec. 31, 2018
Jun. 30, 2018
Mar. 31, 2018
Dec. 31, 2017
Derivative [Line Items]            
Notional $ 55,549,424,000 $ 58,777,783,000 $ 36,528,169,000 $ 28,618,861,000 $ 18,429,288,000 $ 31,226,878,000
Derivative Financial Instruments, Liabilities [Member]            
Derivative [Line Items]            
Notional 38,034,813,000   5,403,265,000      
Fair Value $ (255,000)   (820,590,000)      
Short US Treasuries [Member]            
Derivative [Line Items]            
Fair Value     781,500,000      
Short US Treasuries [Member] | Derivative Financial Instruments, Liabilities [Member]            
Derivative [Line Items]            
Notional     800,000,000      
Fair Value     $ (781,455,000)