Net Asset Value and Financial Highlights - Schedule of Net Asset Value Per Share (Detail) - $ / shares	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Net Asset Value
Net asset value per Share, beginning of period	$ 11.87	$ 15.99
Net realized and change in unrealized gain (loss) on United States Treasury Obligations and Commodity Futures Contracts	0.56	(0.76)
Net investment income (loss)	(0.02)	(0.03)
Net income (loss)	0.54	(0.79)
Net asset value per Share, end of period	12.41	15.20
Market value per Share, beginning of period	11.91	15.91
Market value per Share, end of period	$ 12.41	$ 15.17
Ratio to average Net Assets
Net investment income (loss)	(0.82%)	(0.80%)
Total expenses	1.03%	0.82%
Total Return, at net asset value	4.55%	(4.94%)
Total Return, at market value	4.20%	(4.65%)