Note 8 - Financial Highlights (Details) - Financial Highlights (USD $)	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014
Financial Highlights [Abstract]
Net asset value per Share, beginning of period	$ 11.61	[1]	$ 11.66
Net increase (decrease) in net assets from operations	$ (0.13)		$ 0.86
Net asset value per Share, end of period	$ 11.48		$ 12.52
Total return, at net asset value(c)(d)	(1.12%)	[2],[3]	7.38%	[2],[3]
Ratio to average net assets:
Net investment loss(e)	(0.25%)	[4]	(0.25%)	[4]
Expenses(e)	0.25%	[4]	0.25%	[4]
Net investment loss(a)	$ (0.01)	[5]	$ (0.01)	[5]
Net realized and unrealized gain (loss)(b)	$ (0.12)	[6]	$ 0.87	[6]

[1] Previously reported as "Balance Sheets." Please refer to Note 2A.

[2] Based on the change in net asset value of a Share during the period.

[3] Percentage is not annualized.

[4] Percentage is annualized.

[5] Based on average Shares outstanding during the period.

[6] The amounts reported for a Share outstanding may not accord with the change in aggregate gains and losses on investment for the period due to the timing of Trust Share transactions in relation to the fluctuating fair values of the Trust's underlying investment.