Financial Highlights - Schedule of Net Asset Value Per Share (Detail) - $ / shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Net Asset Value
Net asset value per Share, beginning of period	$ 14.44	$ 16.63
Net realized and change in unrealized gain (loss) on United States Treasury Obligations, Affiliated Investments and Commodity Futures Contracts	1.41	0.30
Net investment income (loss)	0.06	0.02
Net income (loss)	1.47	0.32
Net asset value per Share, end of period	15.91	16.95
Market value per Share, beginning of period	14.51	16.62
Market value per Share, end of period	$ 15.91	$ 16.98
Ratio to average Net Assets
Net investment income (loss)	1.51%	0.42%
Expenses, after waivers	0.90%	0.86%
Expenses, prior to waivers	0.92%	0.88%
Total Return, at net asset value	10.18%	1.92%
Total Return, at market value	9.65%	2.17%