Organization - Additional Information (Detail)		6 Months Ended
	Feb. 23, 2015 USD ($) shares	Jun. 30, 2017 Basket shares	Dec. 31, 2016 shares	Aug. 03, 2006 Trust
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Number of series of trusts | Trust				7
Partners' capital contribution | $	$ 1,000
General shares, shares issued	40	40	40
Treasury obligation measurement maximum maturity period		12 months
Number of shares issued per basket		200,000
Minimum number of Baskets that can be purchased | Basket		1