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Australian Dollar Deposits - Additional Information (Detail)
2 Months Ended 12 Months Ended
Dec. 31, 2018
USD ($)
Dec. 31, 2018
AUD ($)
Dec. 31, 2017
USD ($)
Oct. 31, 2018
USD ($)
Oct. 31, 2018
AUD ($)
Oct. 31, 2017
USD ($)
Oct. 31, 2017
AUD ($)
Dec. 31, 2018
AUD ($)
Oct. 31, 2018
AUD ($)
Oct. 31, 2017
AUD ($)
Cash and Cash Equivalents [Abstract]                    
Principal deposits $ 7,287,860 $ 10,000,000 $ 3,819,070 $ 18,880,911 $ 25,000,000 $ 34,369,885 $ 45,000,000      
Principal redemptions 10,854,234 $ 15,000,000 $ 15,275,524 30,200,732 $ 40,000,000 72,530,089 $ 95,000,000      
Deposits, interest bearing $ 116,159,963     $ 120,487,478   $ 141,848,757   $ 165,000,000 $ 170,000,000 $ 185,000,000
Annual nominal rate (0.06%) (0.06%)