Note 10 - Investment Valuation (Tables)

12 Months Ended

Dec. 31, 2019

Notes Tables

Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Table Text Block]

	Level 1			Level 2		Level 3		Total
December 31, 2019
Futures contracts(a)	$	19,634,651		$	—	$	—	$	19,634,651
U.S. Treasury bills		—			750,519,365		—		750,519,365
December 31, 2018
Futures contracts(a)	$	(116,523,249	)	$	—	$	—	$	(116,523,249	)
U.S. Treasury bills		—			1,199,726,652		—		1,199,726,652