Note 9 - Investing in Index Futures (Tables)

9 Months Ended

Sep. 30, 2015

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block]

	Asset Derivatives	Fair Value		Liability Derivatives	Fair Value
September 30, 2015
Commodity contracts	Receivable for variation margin on open futures contracts	$	6,562,418	Payable for variation margin on open futures contracts	$	—
December 31, 2014
Commodity contracts	Receivable for variation margin on open futures contracts	$	—	Payable for variation margin on open futures contracts	$	7,717,674

Derivative Instruments, Gain (Loss) [Table Text Block]

	Statements of Operations Location	Net Realized Gain (Loss)			Net Change in Unrealized Appreciation/Depreciation
Three Months Ended September 30, 2015
Commodity contracts	Net realized gain (loss) from futures contracts	$	(152,499,032	)	$	—
	Net change in unrealized appreciation/depreciation on futures contracts		—			(15,131,979	)
Three Months Ended September 30, 2014
Commodity contracts	Net realized gain (loss) from futures contracts	$	(99,275,900	)	$	—
	Net change in unrealized appreciation/depreciation on futures contracts		—			(43,732,303	)

Nine Months Ended September 30, 2015
Commodity contracts	Net realized gain (loss) from futures contracts	$	(222,057,163	)	$	—
	Net change in unrealized appreciation/depreciation on futures contracts		—			52,483,833
Nine Months Ended September 30, 2014
Commodity contracts	Net realized gain (loss) from futures contracts	$	(138,661,150	)	$	—
	Net change in unrealized appreciation/depreciation on futures contracts		—			49,609,765