Note 2 - Summary of Significant Accounting Policies - Concentration Risk (Details) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018	Jun. 30, 2018
Revenue, related parties	$ 3,567,702	$ 4,345,234	$ 11,729,689	$ 14,348,806
Customer Concentration Risk [Member] | Revenue Benchmark [Member] | Wainwright [Member]
Revenue, related parties	$ 3,567,702	$ 4,345,234	$ 11,729,689	$ 14,348,806
Concentration risk percentage	100.00%	100.00%	100.00%	100.00%
Customer Concentration Risk [Member] | Revenue Benchmark [Member] | Wainwright [Member] | Customers Related to the USO Fund [Member]
Revenue, related parties	$ 1,803,427	$ 2,187,506	$ 5,641,829	$ 7,630,965
Concentration risk percentage	51.00%	50.00%	48.00%	53.00%
Customer Concentration Risk [Member] | Revenue Benchmark [Member] | Wainwright [Member] | Customers Related to the USCI Fund [Member]
Revenue, related parties	$ 912,419	$ 1,038,924	$ 3,262,108	$ 2,996,917
Concentration risk percentage	25.00%	24.00%	28.00%	21.00%
Customer Concentration Risk [Member] | Revenue Benchmark [Member] | Wainwright [Member] | Customers Related to the UNG Fund [Member]
Revenue, related parties	$ 432,915	$ 648,691	$ 1,510,303	$ 2,220,710
Concentration risk percentage	12.00%	15.00%	13.00%	16.00%
Customer Concentration Risk [Member] | Revenue Benchmark [Member] | Wainwright [Member] | All Other Customers [Member]
Revenue, related parties	$ 418,941	$ 470,113	$ 1,315,449	$ 1,500,214
Concentration risk percentage	12.00%	11.00%	11.00%	10.00%
Customer Concentration Risk [Member] | Accounts Receivable [Member] | Wainwright [Member]
Revenue, related parties			$ 1,207,361		$ 1,458,159
Concentration risk percentage			100.00%		100.00%
Customer Concentration Risk [Member] | Accounts Receivable [Member] | Wainwright [Member] | Customers Related to the USO Fund [Member]
Revenue, related parties			$ 598,810		$ 674,535
Concentration risk percentage			49.00%		46.00%
Customer Concentration Risk [Member] | Accounts Receivable [Member] | Wainwright [Member] | Customers Related to the USCI Fund [Member]
Revenue, related parties			$ 309,916		$ 431,288
Concentration risk percentage			26.00%		30.00%
Customer Concentration Risk [Member] | Accounts Receivable [Member] | Wainwright [Member] | Customers Related to the UNG Fund [Member]
Revenue, related parties			$ 142,351		$ 182,399
Concentration risk percentage			12.00%		12.00%
Customer Concentration Risk [Member] | Accounts Receivable [Member] | Wainwright [Member] | All Other Customers [Member]
Revenue, related parties			$ 156,284		$ 169,937
Concentration risk percentage			13.00%		12.00%