Organization - Additional Information (Detail)		12 Months Ended
	May 23, 2005 USD ($) shares	Dec. 31, 2016 Basket shares	Dec. 31, 2015 shares
Organization Consolidation And Presentation Of Financial Statements [Abstract]
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