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Australian Dollar Deposits - Additional Information (Detail)
2 Months Ended 3 Months Ended
Dec. 31, 2018
AUD ($)
Mar. 31, 2019
USD ($)
Mar. 31, 2019
AUD ($)
Mar. 31, 2018
USD ($)
Mar. 31, 2019
AUD ($)
Dec. 31, 2018
USD ($)
Dec. 31, 2018
AUD ($)
Cash And Cash Equivalents [Abstract]              
Annual nominal rate   1.29% 1.29%        
Principal deposits $ 10,000,000 $ 7,094,912 $ 10,000,009        
Principal redemptions $ 15,000,000 17,792,563 $ 24,999,877 $ 3,929,418      
Deposits, interest bearing   $ 106,552,574     $ 150,000,132 $ 116,159,963 $ 165,000,000