Organization - Additional Information (Detail)		12 Months Ended
	Aug. 03, 2006 USD ($) Trust shares	Dec. 31, 2016 Basket shares	Dec. 31, 2015 shares	Oct. 24, 2014 Trust
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Number of series of trusts | Trust	2			2
Partners' capital contribution | $	$ 1,000
General shares, shares issued	40	40	40
Minimum number of Baskets that can be purchased | Basket		1
Number of shares issued per basket		200,000