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Fair Value Measurements (Details) - USD ($)
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Reconciliation of changes in fair value measurement, assets [abstract]    
Balance at beginning of year $ 954,587,514  
Realized losses on sales and redemptions for physical bullion (5,400,608) $ (966,565)
Change in unrealized gains (losses) (76,160,284) 57,726,059
Balance at end of year 871,613,584 954,587,514
Recurring fair value measurement    
Reconciliation of changes in fair value measurement, assets [abstract]    
Balance at beginning of year 954,587,514 885,981,474
Purchases 7,501,519 13,450,769
Sales (1,169,773) (1,604,223)
Redemptions for physical bullion (7,744,784)  
Realized losses on sales and redemptions for physical bullion (5,400,608) (966,565)
Change in unrealized gains (losses) (76,160,284) 57,726,059
Balance at end of year $ 871,613,584 $ 954,587,514