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Represents collection period for other than municipalities.

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Represents percentage of retainage balance for retainage receivables aged greater than 365 days.

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The amount of increase (decrease) in fair value of the reporting unit.

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The percentage of amount increase(decrease) in fair value of the reporting unit.

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Percentage of carrying amount of reporting unit in excess of fair value.

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Represents collection period upon completion of contract for retainage.

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Represents information related to percent of contract value withheld for retainage.

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Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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Amount before tax of foreign currency transaction realized gain (loss) recognized in the income statement.

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Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount after tax of reclassification adjustment from accumulated other comprehensive income for translation gain (loss) realized upon the sale or liquidation of an investment in a foreign entity and foreign currency hedges that are designated and qualified as hedging instruments for hedges of the foreign currency exposure of a net investment in a foreign operation.

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The aggregate costs incurred (1) in a planned search or critical investigation aimed at discovery of new knowledge with the hope that such knowledge will be useful in developing a new product or service, a new process or technique, or in bringing about a significant improvement to an existing product or process; or (2) to translate research findings or other knowledge into a plan or design for a new product or process or for a significant improvement to an existing product or process whether intended for sale or the entity's use, during the reporting period charged to research and development projects, including the costs of developing computer software up to the point in time of achieving technological feasibility, and costs allocated in accounting for a business combination to in-process projects deemed to have no alternative future use.

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Note 2 - Accounting Policies (Details Textual) $ in Thousands	1 Months Ended	3 Months Ended	12 Months Ended
	Oct. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($) shares	Oct. 01, 2019
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale or Liquidation, Net of Tax, Total			$ 300	$ 10,900
Foreign Currency Transaction Gain (Loss), Realized			(844)	(503)	$ (623)
Research and Development Expense, Total			$ 4,900	6,400	5,600
Retainage Collection Period Upon Completion of Contract (Year)			1 year
Percentage of Retainage Balance, Retainage Receivables Aged Greater than 365 Days			14.00%
Goodwill, Impairment Loss			$ 0	0	1,389
Goodwill, Ending Balance			$ 210,665	$ 208,858	$ 212,656
Number of Reporting Units	6
Energy Services [Member]
Reporting Unit, Percentage of Carrying Amount in Excess of Fair Value		31.30%
Reporting Unit, Increase (Decrease) in Fair Value		$ (67,800)
Reporting Unit, Increase (Decrease) in Fair Value, Percentage		(44.00%)
Goodwill, Impairment Loss		$ 39,400
Goodwill, Ending Balance		$ 7,300
Energy Services [Member] \| Weighted Average Cost of Capital [Member]
Goodwill, Measurement Input		0.150				0.130
Energy Services [Member] \| Measurement Input, Long-term Revenue Growth Rate [Member]
Goodwill, Measurement Input		0.032				0.034
Fyfe [Member]
Goodwill, Impairment Loss	$ 9,800
Minimum [Member]
Construction Period (Month)			1 month
Collection Period for Municipalities (Day)			60 days
Retainage, Percent of Contract Value Withheld			5.00%
Collection Period for Other than Municipalities (Day)			30 days
Minimum [Member] \| Measurement Input, Long-term Revenue Growth Rate [Member]
Goodwill, Measurement Input	0.022
Minimum [Member] \| Measurement Input, Discount Rate [Member]
Goodwill, Measurement Input	0.127
Maximum [Member]
Construction Period (Month)			24 months
Collection Period for Municipalities (Day)			90 days
Retainage, Percent of Contract Value Withheld			15.00%
Collection Period for Other than Municipalities (Day)			45 days
Maximum [Member] \| Measurement Input, Long-term Revenue Growth Rate [Member]
Goodwill, Measurement Input	0.089
Maximum [Member] \| Measurement Input, Discount Rate [Member]
Goodwill, Measurement Input	0.157
Stock Options and Restricted and Deferred Stock Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount (in shares) \| shares				529,539	652,621
Share-based Payment Arrangement, Option [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount (in shares) \| shares					4,049