Note 4 - Impairment Charges (Details Textual) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Goodwill, Impairment Loss		$ 24,413
Equity Method Investment, Other than Temporary Impairment		9,600
Equity Method Investments		74,511	$ 84,176	$ 82,109
Water and Mineral Services Group Materials [Member]
Goodwill, Impairment Loss		14,800
Water and Mineral Services Group Materials [Member] | Subsequent Event [Member]
Goodwill, Impairment Loss	$ 14,400
Water and Minerals Services Group Specialty [Member]
Goodwill, Impairment Loss		$ 0
Reporting Unit, Percentage of Fair Value in Excess of Carrying Amount		15.00%
Water and Mineral Services Group Water [Member] | Subsequent Event [Member]
Goodwill, Impairment Loss	117,900
Midwest Group Specialty [Member] | Subsequent Event [Member]
Goodwill, Impairment Loss	$ 0
Reporting Unit, Percentage of Fair Value in Excess of Carrying Amount	15.00%