Note 1 - Description of Business and Summary of Significant Accounting Policies - Concentration of Credit Risk (Details) - Revenue Benchmark [Member] - Customer Concentration Risk [Member]	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
CIMA [Member]
Concentration risk percentage	39.00%	41.00%
Shell [Member]
Concentration risk percentage	19.00%	0.00%
ETC [Member]
Concentration risk percentage	19.00%	15.00%
CES [Member]
Concentration risk percentage	10.00%	8.00%
Genesis Crude Oil LP [Member]
Concentration risk percentage	8.00%	13.00%
Sunoco, Inc. [Member]
Concentration risk percentage	1.00%	4.00%
Williams Energy Resources LLC [Member]
Concentration risk percentage	0.00%	1.00%
Occidental Energy MA [Member]
Concentration risk percentage	0.00%	1.00%