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CONTRACTS AND AGREEMENTS - Brokerage Commissions (Details) - USD ($) | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Long Duration Contracts Assumptions By Product And Guarantee [Line Items] |  |  |
Brokerage commissions | $ 7,261 | $ 6,045 | $ 17,897
Brokerage commissions as a percentage of average daily net assets | 0.01% | 0.01% | 0.02%
Rebalancing Investments Transaction [Member] |  |  |
Long Duration Contracts Assumptions By Product And Guarantee [Line Items] |  |  |
Brokerage commissions | $ 6,695 | $ 4,961 | $ 13,735
Brokerage commissions as a percentage of average daily net assets | 92.20% | 82.07% | 76.74%
Trades Necessitated By Creation And Redemption Activity [Member] |  |  |
Long Duration Contracts Assumptions By Product And Guarantee [Line Items] |  |  |
Brokerage commissions | $ 566 | $ 1,084 | $ 4,162
Brokerage commissions as a percentage of average daily net assets | 7.80% | 17.93% | 23.26%

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