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Euro Deposits - Additional Information (Detail)
9 Months Ended 12 Months Ended
Sep. 30, 2020
USD ($)
Sep. 30, 2020
EUR (€)
Sep. 30, 2019
USD ($)
Dec. 31, 2019
EUR (€)
Sep. 30, 2020
EUR (€)
Dec. 31, 2019
USD ($)
Dec. 31, 2019
EUR (€)
Cash And Cash Equivalents [Abstract]              
Annual nominal rate (0.50%)       (0.50%)    
Principal deposits $ 334,139,542 € 278,446,723 $ 192,248,072 € 261,604,378      
Principal redemptions 270,204,291 240,874,294 $ 270,071,178 281,022,381      
Withdrawals (to pay expenses)   € 1,618,326   € 1,798,500      
Deposits, interest bearing $ 342,486,152       € 292,061,573 $ 287,480,505 € 256,107,470