XML 58 R36.htm IDEA: XBRL DOCUMENT v3.8.0.1
Derivative Contract Information - Summary of Average Daily Notional Value of Derivative Contracts Outstanding (Detail) - Over-the-Counter ("OTC") [Member] - USD ($)
$ in Thousands
3 Months Ended 12 Months Ended
Mar. 31, 2018
Sep. 30, 2017
Derivative Instruments and Hedging Activities Disclosures [Line Items]    
Gold Delivery Agreement Average notional $ 18,106 $ 22,963
SPDR Long Dollar Gold Trust [Member]    
Derivative Instruments and Hedging Activities Disclosures [Line Items]    
Gold Delivery Agreement Average notional $ 18,106 $ 22,963