Note 2 - Acquisitions (Details Textual) - USD ($) $ in Thousands, shares in Millions			12 Months Ended
	Jun. 14, 2018	Apr. 03, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	May 22, 2019
Business Combination, Consideration Transferred, Equity Interests Issued and Issuable			$ 0	$ 0	$ 321,019
Goodwill, Ending Balance			116,777	264,279
Amortization of Intangible Assets, Total			$ 13,500	$ 18,900	$ 15,200
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent			21.00%	21.00%	21.00%
Pro Forma [Member]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent					26.00%
Water [Member]
Goodwill, Ending Balance			$ 30,780	$ 149,127
Materials [Member]
Goodwill, Ending Balance			25,339	54,488
Specialty [Member]
Goodwill, Ending Balance			$ 40,860	$ 40,866
Layne Christensen Company [Member]
Business Combination, Consideration Transferred, Total	$ 349,840
Business Combination, Consideration Transferred, Equity Interests Issued and Issuable	$ 321,000
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares (in shares)	5.6
Payments to Acquire Businesses, Gross	$ 28,800
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt	191,500
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets, Total	424,316
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill, Total	61,548
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities, Total	323,643
Goodwill, Ending Balance	187,619
Layne Christensen Company [Member] | Water [Member]
Goodwill, Ending Balance	125,700
Layne Christensen Company [Member] | Materials [Member]
Goodwill, Ending Balance	52,500
Layne Christensen Company [Member] | Specialty [Member]
Goodwill, Ending Balance	$ 9,400
LiquiForce [Member]
Payments to Acquire Businesses, Gross		$ 35,900
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets, Total		14,300
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill, Total		10,900
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities, Total		8,500
Goodwill, Ending Balance		19,300
Cash, Ending Balance						$ 6,200
LiquiForce [Member] | Water [Member]
Goodwill, Ending Balance		$ 19,200
Layne and LiquiForce Acquisitions [Member]
Amortization of Intangible Assets, Total					$ 12,200