Net Asset Value and Financial Highlights - Schedule of Net Asset Value Per Share (Detail) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Net Asset Value
Net asset value per Share, beginning of period	$ 24.89	$ 25.01	$ 25.65	$ 23.98
Net realized and change in unrealized gain (loss) on United States Treasury Obligations and Currency Futures Contracts	(0.19)	0.17	(0.88)	1.29
Net investment income (loss)	(0.03)	(0.05)	(0.10)	(0.14)
Net income (loss)	(0.22)	0.12	(0.98)	1.15
Net asset value per Share, end of period	24.67	25.13	24.67	25.13
Market value per Share, beginning of period	24.85	25.02	25.64	23.98
Market value per Share, end of period	$ 24.68	$ 25.12	$ 24.68	$ 25.12
Ratio to average Net Assets
Net investment income (loss)	(0.50%)	(0.77%)	(0.54%)	(0.76%)
Expenses, after waivers	0.77%	0.79%	0.78%	0.78%
Expenses, prior to waivers	0.78%	0.79%	0.78%	0.78%
Total Return, at net asset value	(0.88%)	0.48%	(3.82%)	4.79%
Total Return, at market value	(0.69%)	0.40%	(3.74%)	4.75%