Note 1 - Description of Business	12 Months Ended
Dec. 31, 2020
Notes to Financial Statements
Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block]	1. DESCRIPTION OF BUSINESS Aegion Corporation combines innovative technologies with market leading expertise to maintain, rehabilitate and strengthen pipelines and other infrastructure around the world. For 50 years, the Company has played a pioneering role in finding transformational solutions to rehabilitate aging infrastructure, primarily pipelines in the wastewater, water, energy, mining and refining industries. The Company also maintains the efficient operation of refineries and other industrial facilities and provides innovative solutions for the strengthening of buildings, bridges and other structures. Aegion is committed to Stronger. Safer. Infrastructure^®. The Company believes that the depth and breadth of its products and services platform make Aegion a leading “one-stop” provider for the world’s infrastructure rehabilitation and protection needs. The Company is primarily built on the premise that it is possible to use technology to extend the structural design life and maintain, if not improve, the performance of infrastructure, mostly pipe. The Company is proving that this expertise can be applied in a variety of markets to protect pipelines in oil, gas, mining, wastewater and water applications and extending this to the rehabilitation and maintenance of commercial structures and the provision of professional services in energy-related industries. Many types of infrastructure must be protected from the corrosive and abrasive materials that pass through or near them. The Company’s expertise in non-disruptive corrosion engineering and abrasion protection is now wide-ranging, opening new markets for growth. The Company has a long history of product development and intellectual property management. The Company manufactures most of the engineered solutions it creates as well as the specialized equipment required to install them. Finally, decades of experience give the Company an advantage in understanding municipal, energy, mining, industrial and commercial customers. Strong customer relationships and brand recognition allow the Company to support the expansion of existing and innovative technologies into new high growth markets. The Company’s predecessor was originally incorporated in Delaware in 1980 to act as the exclusive United States licensee of the Insituform^® cured-in-place pipe (“CIPP”) process, which Insituform’s founder invented in 1971. The Insituform^® CIPP process served as the first trenchless technology for rehabilitating sewer pipelines and has enabled municipalities and private industry to avoid the extraordinary expense and extreme disruption that can result from conventional “dig-and-replace” methods. For 50 years, the Company has maintained its leadership position in the CIPP market from manufacturing to technological innovations and market share. In order to strengthen the Company’s ability to service the emerging demands of the infrastructure protection market and to better position the Company for sustainable growth, the Company embarked on a diversification strategy in 2009 to expand its product and service portfolio and its geographical reach. Through a series of strategic initiatives and key acquisitions, the Company now possesses a broad portfolio of cost-effective solutions for rehabilitating and maintaining aging or deteriorating infrastructure, protecting new infrastructure from corrosion worldwide and providing integrated professional services in engineering, procurement, construction, maintenance, and turnaround services for oil and natural gas companies, primarily in the midstream and downstream markets. Recognizing that the breadth of offerings expanded beyond the Company’s flagship Insituform^®brand, which constituted less than half of the Company’s revenues in 2011, the Company reorganized Insituform Technologies, Inc. (“Insituform”), the parent company at the time, into a new holding company structure in October 2011. Aegion became the new parent company and Insituform became a wholly-owned subsidiary of Aegion. Aegion reflects the Company’s mission of extending its leadership capabilities to furnish products and services to provide: (i) long-term protection for water and wastewater pipes, oil and gas pipelines and infrastructure as well as commercial and governmental structures and transportation infrastructure; and (ii) integrated professional services to energy companies. Strategic Initiatives/Acquisitions/Divestitures Pending Merger On February 16, 2021, the Company entered into a definitive merger agreement with affiliates of New Mountain Capital, L.L.C., a leading growth-oriented investment firm headquartered in New York. The transaction is valued at approximately $963 million, or $26.00 per common share, and was unanimously approved by the Company’s board of directors. Upon completion of the transaction, Aegion will become a private company and shares of Aegion common stock will no longer be listed on any public market. The merger is expected to close in the second quarter of 2021, subject to customary closing conditions, including, among other things, approval under the Hart-Scott-Rodino Antitrust Improvements Act of 1976 (the “HSR Act”) and approval of the Company’s stockholders. In connection with the merger, any unvested restricted stock units and performance stock units will become fully vested at the time of the completed transaction and convert into the right to receive a cash payment equal to the per share transaction valuation. This conversion could be material. The merger agreement also includes customary termination provisions for both parties, subject, in certain circumstances, to the payment by the Company of a termination fee of $30,000,000. Discontinued Operations In December 2020, the Company’s board of directors approved a divestiture plan for the Energy Services reportable segment (“Energy Services”). This decision reflects an advancement of the Company’s strategy to expand its focus on core water and wastewater markets, while reducing its exposure to the oil and gas markets. The results of the former Energy Services segment are presented as discontinued operations and have been excluded from both continuing operations and segment results for the years ended December 31, 2020, 2019 and 2018. The Company has classified Energy Services’s assets and liabilities as held for sale on the Consolidated Balance Sheets at December 31, 2020 and 2019. See Note 6. Restructuring Activities In 2017, the Company’s board of directors approved a comprehensive global realignment and restructuring plan (the “Restructuring”) intended to generate more predictable and sustainable long‐term earnings growth, which included, among other things, actions to reduce upstream oil & gas exposure, the exit or divestiture of multiple smaller international businesses, the restructuring of unprofitable businesses in North America and other efforts to right‐size underperforming businesses and reduce corporate and other operating costs. See further discussion in Note 4. Infrastructure Solutions Segment (“Infrastructure Solutions”) In February 2020, the Company sold its Spanish CIPP contracting entity, Insituform Technologies Iberica, S.A. (“Insituform Spain”), to Lajusocarley S.L. In connection with the sale, the Company entered into a five-year tube supply agreement whereby Insituform Spain will buy felt liners exclusively from the Company. Insituform Spain is also entitled to use the Insituform® trade name in Spain based on a trademark license granted for the same five-year time period. The Company had classified Insituform Spain’s assets and liabilities as held for sale on the Consolidated Balance Sheet at December 31, 2019. See Note 6. In January 2020, the Company sold its Australian CIPP contracting entity, Insituform Pacific Pty Limited (“Insituform Australia”), to Insituform Holdings Pty Ltd, an entity affiliated with Killard Infrastructure Pty Ltd. In connection with the sale, the Company entered into a five-year tube supply agreement whereby Insituform Australia, under its new ownership, will buy liners exclusively from the Company. Insituform Australia is also entitled to use the Insituform® trade name in Australia based on a trademark license granted for the same five-year time period. The Company had classified Insituform Australia’s assets and liabilities as held for sale on the Consolidated Balance Sheet at December 31, 2019. See Note 6. During 2019, the Company initiated plans to sell its contracting business in Northern Ireland, Environmental Techniques Limited (“Environmental Techniques”). Accordingly, the Company has classified the assets and liabilities of this business as held for sale on the Consolidated Balance Sheets at December 31, 2020 and 2019. The Company temporarily suspended the sales process for Environmental Techniques due to COVID-19 and expects to recommence the process during the second half of 2021. See Note 6. In October 2019, the Company sold its CIPP contracting operations of Insituform Netherlands to GMB Rioleringstechnieken B.V., a Dutch company (“GMB”). In connection with the sale, the Company entered into a five-year tube supply agreement whereby GMB will buy liners from the Company. In November 2018, the Company sold substantially all of the fixed assets and inventory from its CIPP operations in Denmark. In connection with the sale, the Company entered into a five-year exclusive tube-supply agreement whereby the buyers will purchase Insituform^® CIPP liners from the Company. The buyers are also entitled to use the Insituform^® trade name based on a trademark license granted for the same five-year time period. Corrosion Protection Segment (“Corrosion Protection”) In October 2019, the Company sold its fifty-five percent (55%) interest in United Mexico, its Mexican Tite Liner^® joint venture, to its joint venture partner, Miller Pipeline de Mexico, S.A. de C.V., a Mexican company (“Miller”). Miller owned the remaining forty-five percent (45%) interest in United Mexico. In connection with the sale, the Company entered into a long-term license agreement pursuant to which United Mexico will be the exclusive licensee in Mexico with respect to certain trademarks, patents and other intellectual property relating to the Company’s pipe lining business. In August 2018, the Company sold substantially all of the assets of its wholly-owned subsidiary, The Bayou Companies, LLC and its fifty-one percent (51%) interest in Bayou Wasco Insulation, LLC. The sale price was $46 million, consisting of $38 million paid in cash at closing and $8 million in a fully secured, two-year loan payable to Aegion. During 2020, the loan was extended and now has a maturity date in March 2021. Cash proceeds, net of customary closing costs, were used to repay outstanding borrowings on the Company’s line of credit. The sale resulted in a pre-tax loss of $7.0 million during 2018, which was included in “Other expense” in the Consolidated Statements of Operations. In May 2018, the Company acquired the operations of Hebna Inc., Hebna Canada Inc. and Hebna Corporation (collectively “Hebna”), for a purchase price of $6.0 million, which included goodwill of $2.7 million, intangible assets of $2.4 million, and property, plant and equipment of $0.9 million. The transaction was funded from a combination of domestic and international cash balances, with fifty percent (50%) of the purchase price being paid by the Company’s joint venture in Oman, in which the Company is a fifty-one percent (51%) partner. Hebna provides pipeline lining services, including compressed-fit lining, slip-lining, liner and free-standing pipe fusing, pipeline assessment and integrity management, pipeline pigging and calibration, and roto-lining services primarily in the United States, Canada and Middle East.

Note 1 - Description of Business

12 Months Ended

Dec. 31, 2020

Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block]

1. DESCRIPTION OF BUSINESS

Aegion Corporation combines innovative technologies with market leading expertise to maintain, rehabilitate and strengthen pipelines and other infrastructure around the world. For 50 years, the Company has played a pioneering role in finding transformational solutions to rehabilitate aging infrastructure, primarily pipelines in the wastewater, water, energy, mining and refining industries. The Company also maintains the efficient operation of refineries and other industrial facilities and provides innovative solutions for the strengthening of buildings, bridges and other structures. Aegion is committed to Stronger. Safer. Infrastructure^®. The Company believes that the depth and breadth of its products and services platform make Aegion a leading “one-stop” provider for the world’s infrastructure rehabilitation and protection needs.

The Company is primarily built on the premise that it is possible to use technology to extend the structural design life and maintain, if not improve, the performance of infrastructure, mostly pipe. The Company is proving that this expertise can be applied in a variety of markets to protect pipelines in oil, gas, mining, wastewater and water applications and extending this to the rehabilitation and maintenance of commercial structures and the provision of professional services in energy-related industries. Many types of infrastructure must be protected from the corrosive and abrasive materials that pass through or near them. The Company’s expertise in non-disruptive corrosion engineering and abrasion protection is now wide-ranging, opening new markets for growth. The Company has a long history of product development and intellectual property management. The Company manufactures most of the engineered solutions it creates as well as the specialized equipment required to install them. Finally, decades of experience give the Company an advantage in understanding municipal, energy, mining, industrial and commercial customers. Strong customer relationships and brand recognition allow the Company to support the expansion of existing and innovative technologies into new high growth markets.

The Company’s predecessor was originally incorporated in Delaware in 1980 to act as the exclusive United States licensee of the Insituform^® cured-in-place pipe (“CIPP”) process, which Insituform’s founder invented in 1971. The Insituform^® CIPP process served as the first trenchless technology for rehabilitating sewer pipelines and has enabled municipalities and private industry to avoid the extraordinary expense and extreme disruption that can result from conventional “dig-and-replace” methods. For 50 years, the Company has maintained its leadership position in the CIPP market from manufacturing to technological innovations and market share.

In order to strengthen the Company’s ability to service the emerging demands of the infrastructure protection market and to better position the Company for sustainable growth, the Company embarked on a diversification strategy in 2009 to expand its product and service portfolio and its geographical reach. Through a series of strategic initiatives and key acquisitions, the Company now possesses a broad portfolio of cost-effective solutions for rehabilitating and maintaining aging or deteriorating infrastructure, protecting new infrastructure from corrosion worldwide and providing integrated professional services in engineering, procurement, construction, maintenance, and turnaround services for oil and natural gas companies, primarily in the midstream and downstream markets.

Recognizing that the breadth of offerings expanded beyond the Company’s flagship Insituform^®brand, which constituted less than half of the Company’s revenues in 2011, the Company reorganized Insituform Technologies, Inc. (“Insituform”), the parent company at the time, into a new holding company structure in October 2011. Aegion became the new parent company and Insituform became a wholly-owned subsidiary of Aegion. Aegion reflects the Company’s mission of extending its leadership capabilities to furnish products and services to provide: (i) long-term protection for water and wastewater pipes, oil and gas pipelines and infrastructure as well as commercial and governmental structures and transportation infrastructure; and (ii) integrated professional services to energy companies.

Strategic Initiatives/Acquisitions/Divestitures

Pending Merger

On February 16, 2021, the Company entered into a definitive merger agreement with affiliates of New Mountain Capital, L.L.C., a leading growth-oriented investment firm headquartered in New York. The transaction is valued at approximately $963 million, or $26.00 per common share, and was unanimously approved by the Company’s board of directors. Upon completion of the transaction, Aegion will become a private company and shares of Aegion common stock will no longer be listed on any public market. The merger is expected to close in the second quarter of 2021, subject to customary closing conditions, including, among other things, approval under the Hart-Scott-Rodino Antitrust Improvements Act of 1976 (the “HSR Act”) and approval of the Company’s stockholders. In connection with the merger, any unvested restricted stock units and performance stock units will become fully vested at the time of the completed transaction and convert into the right to receive a cash payment equal to the per share transaction valuation. This conversion could be material. The merger agreement also includes customary termination provisions for both parties, subject, in certain circumstances, to the payment by the Company of a termination fee of $30,000,000.

Discontinued Operations

In December 2020, the Company’s board of directors approved a divestiture plan for the Energy Services reportable segment (“Energy Services”). This decision reflects an advancement of the Company’s strategy to expand its focus on core water and wastewater markets, while reducing its exposure to the oil and gas markets. The results of the former Energy Services segment are presented as discontinued operations and have been excluded from both continuing operations and segment results for the years ended December 31, 2020, 2019 and 2018. The Company has classified Energy Services’s assets and liabilities as held for sale on the Consolidated Balance Sheets at December 31, 2020 and 2019. See Note 6.

Restructuring Activities

In 2017, the Company’s board of directors approved a comprehensive global realignment and restructuring plan (the “Restructuring”) intended to generate more predictable and sustainable long‐term earnings growth, which included, among other things, actions to reduce upstream oil & gas exposure, the exit or divestiture of multiple smaller international businesses, the restructuring of unprofitable businesses in North America and other efforts to right‐size underperforming businesses and reduce corporate and other operating costs. See further discussion in Note 4.

Infrastructure Solutions Segment (“Infrastructure Solutions”)

In February 2020, the Company sold its Spanish CIPP contracting entity, Insituform Technologies Iberica, S.A. (“Insituform Spain”), to Lajusocarley S.L. In connection with the sale, the Company entered into a five-year tube supply agreement whereby Insituform Spain will buy felt liners exclusively from the Company. Insituform Spain is also entitled to use the Insituform® trade name in Spain based on a trademark license granted for the same five-year time period. The Company had classified Insituform Spain’s assets and liabilities as held for sale on the Consolidated Balance Sheet at December 31, 2019. See Note 6.

In January 2020, the Company sold its Australian CIPP contracting entity, Insituform Pacific Pty Limited (“Insituform Australia”), to Insituform Holdings Pty Ltd, an entity affiliated with Killard Infrastructure Pty Ltd. In connection with the sale, the Company entered into a five-year tube supply agreement whereby Insituform Australia, under its new ownership, will buy liners exclusively from the Company. Insituform Australia is also entitled to use the Insituform® trade name in Australia based on a trademark license granted for the same five-year time period. The Company had classified Insituform Australia’s assets and liabilities as held for sale on the Consolidated Balance Sheet at December 31, 2019. See Note 6.

During 2019, the Company initiated plans to sell its contracting business in Northern Ireland, Environmental Techniques Limited (“Environmental Techniques”). Accordingly, the Company has classified the assets and liabilities of this business as held for sale on the Consolidated Balance Sheets at December 31, 2020 and 2019. The Company temporarily suspended the sales process for Environmental Techniques due to COVID-19 and expects to recommence the process during the second half of 2021. See Note 6.

In October 2019, the Company sold its CIPP contracting operations of Insituform Netherlands to GMB Rioleringstechnieken B.V., a Dutch company (“GMB”). In connection with the sale, the Company entered into a five-year tube supply agreement whereby GMB will buy liners from the Company.

In November 2018, the Company sold substantially all of the fixed assets and inventory from its CIPP operations in Denmark. In connection with the sale, the Company entered into a five-year exclusive tube-supply agreement whereby the buyers will purchase Insituform^® CIPP liners from the Company. The buyers are also entitled to use the Insituform^® trade name based on a trademark license granted for the same five-year time period.

Corrosion Protection Segment (“Corrosion Protection”)

In October 2019, the Company sold its fifty-five percent (55%) interest in United Mexico, its Mexican Tite Liner^® joint venture, to its joint venture partner, Miller Pipeline de Mexico, S.A. de C.V., a Mexican company (“Miller”). Miller owned the remaining forty-five percent (45%) interest in United Mexico. In connection with the sale, the Company entered into a long-term license agreement pursuant to which United Mexico will be the exclusive licensee in Mexico with respect to certain trademarks, patents and other intellectual property relating to the Company’s pipe lining business.

In August 2018, the Company sold substantially all of the assets of its wholly-owned subsidiary, The Bayou Companies, LLC and its fifty-one percent (51%) interest in Bayou Wasco Insulation, LLC. The sale price was $46 million, consisting of $38 million paid in cash at closing and $8 million in a fully secured, two-year loan payable to Aegion. During 2020, the loan was extended and now has a maturity date in March 2021. Cash proceeds, net of customary closing costs, were used to repay outstanding borrowings on the Company’s line of credit. The sale resulted in a pre-tax loss of $7.0 million during 2018, which was included in “Other expense” in the Consolidated Statements of Operations.

In May 2018, the Company acquired the operations of Hebna Inc., Hebna Canada Inc. and Hebna Corporation (collectively “Hebna”), for a purchase price of $6.0 million, which included goodwill of $2.7 million, intangible assets of $2.4 million, and property, plant and equipment of $0.9 million. The transaction was funded from a combination of domestic and international cash balances, with fifty percent (50%) of the purchase price being paid by the Company’s joint venture in Oman, in which the Company is a fifty-one percent (51%) partner. Hebna provides pipeline lining services, including compressed-fit lining, slip-lining, liner and free-standing pipe fusing, pipeline assessment and integrity management, pipeline pigging and calibration, and roto-lining services primarily in the United States, Canada and Middle East.