Net Asset Value and Financial Highlights (Details) - $ / shares		3 Months Ended
		Sep. 30, 2017	Sep. 30, 2016
Net Asset Value [Roll Forward]
Net asset value per Share, beginning of period		$ 23.15	$ 22.33
Net investment income (loss)		(0.04)	(0.08)
Net realized and unrealized gain (loss)		0.01	0.31
Net Income (Loss)		(0.03)	0.23
Net Asset Value per Share, end of period		23.12	22.56
Market Value per Share, end of period		$ 23.03	$ 22.52	[1]
Ratios to Average Net Assets [Roll Forward]
Expense Ratio	[2],[3]	1.65%	1.70%
Expense Ratio before Waiver/Assumption	[2],[3]	2.35%	4.64%
Net Investment Income (Loss)	[3]	0.66%	1.48%
Total Return, at Net Asset Value	[3],[4]	(0.13%)	1.03%
Total Return, at Market Value	[3],[4]	0.04%	5.28%

[1] Represents the closing bid/ask mean as of September 30, 2016.

[2] As of February 19, 2015, Fund expenses have been capped at 1.50% of average daily net assets, plus brokerage commissions and interest expense, as disclosed in Note 4.

[3] Percentages are annualized.

[4] Percentages are not annualized.