Note 7 - Commitments and Contingencies (Details Textual) - USD ($)		6 Months Ended	12 Months Ended
	May 18, 2015	Jun. 30, 2017	Dec. 31, 2016
Workers’ Compensation Insurance, Deductible per Occurrence		$ 1,000,000
Automobile Liability Insurance, Deductible per Occurrence		1,000,000
Sudden and Accidental Pollution Claims Insurance, Deductible per Occurrence		250,000
General Liability Claims Insurance, Deductible per Occurrence		250,000
Property Damage Insurance, Deductible per Occurrence		50,000
Excess Loss Liabilities Insurance, Deductible per Occurrence		5,000,000
ESPCT [Member]
Business Combination, Consideration Transferred			$ 34,000,000
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High	$ 29,500,000
Business Combination, Contingent Consideration, Liability	$ 14,400,000	$ 0
Business Combination Contingent Consideration Arrangements Period	3 years