Significant Accounting Policies (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Significant Accounting Policies [Abstract]
Basket of shares	50,000
Fair value transfers	$ 0	$ 0
Reserve for uncertain tax positions	$ 0	$ 0
Annualized rate of Sponsors Fee	0.60%	0.60%	0.60%
Sponsor Fees	$ 1,073,755	$ 1,278,403	$ 1,099,935
Fees payable to Sponsor	89,688	124,409
All other expenses	$ 0	$ 0