Schedule of Investments (Unaudited) - Futures Contracts (Parenthetical) - Contract	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
LME Aluminum (863 contracts, settlement date November 14, 2016)
Schedule of Investments [Line Items]
Open Future Contracts Written, Number of Contracts	863
Futures Contract Indexed to Issuer's Equity, Settlement Date or Dates	Nov. 14, 2016
LME Copper (268 contracts, settlement date May 16, 2016)
Schedule of Investments [Line Items]
Open Future Contracts Written, Number of Contracts	268
Futures Contract Indexed to Issuer's Equity, Settlement Date or Dates	May 16, 2016
LME Zinc (789 contracts, settlement date December 19, 2016)
Schedule of Investments [Line Items]
Open Future Contracts Written, Number of Contracts	789
Futures Contract Indexed to Issuer's Equity, Settlement Date or Dates	Dec. 19, 2016
LME Aluminum (1,012 contracts, settlement date November 14, 2016)
Schedule of Investments [Line Items]
Open Future Contracts Written, Number of Contracts		1,012
Futures Contract Indexed to Issuer's Equity, Settlement Date or Dates		Nov. 14, 2016
LME Copper (314 contracts, settlement date February 15, 2016)
Schedule of Investments [Line Items]
Open Future Contracts Written, Number of Contracts		314
Futures Contract Indexed to Issuer's Equity, Settlement Date or Dates		Feb. 15, 2016
LME Zinc (949 contracts, settlement date February 15, 2016)
Schedule of Investments [Line Items]
Open Future Contracts Written, Number of Contracts		949
Futures Contract Indexed to Issuer's Equity, Settlement Date or Dates		Feb. 15, 2016