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Statements of Changes in Partners' Capital (Parenthetical) - shares
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Statement of Changes in Partners' Capital      
Addition of partnership shares 950,000 2,050,000 3,150,000
Redemption of partnership shares 1,750,000 2,400,000 5,150,000