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Australian Dollar Deposits - Additional Information (Detail)
9 Months Ended 12 Months Ended
Jul. 31, 2018
USD ($)
Jul. 31, 2018
AUD ($)
Jul. 31, 2017
USD ($)
Oct. 31, 2017
AUD ($)
Jul. 31, 2018
AUD ($)
Oct. 31, 2017
USD ($)
Oct. 31, 2017
AUD ($)
Cash and Cash Equivalents [Abstract]              
Principal deposits $ 15,330,483 $ 20,000,000 $ 18,876,552 $ 45,000,000      
Principal redemptions 22,987,378 $ 30,000,000 $ 30,191,441 $ 95,000,000      
Deposits, interest bearing $ 130,094,984       $ 175,000,000 $ 141,848,757 $ 185,000,000
Annual nominal rate 1.11% 1.11%