Note 2 - Accounting Policies - Investments in Variable Interest Entities (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019		Dec. 31, 2018
Current assets		$ 477,254	$ 553,103
Current liabilities		224,808	244,376
Revenue	[1]	807,764	885,887		$ 997,861
Gross profit	[1]	196,459	205,001		225,379
Net (income) loss attributable to Aegion Corporation		(31,861)	(20,892)		2,928
Variable Interest Entity, Primary Beneficiary [Member]
Current assets		24,876	18,304
Non-current assets		7,513	7,635
Current liabilities		10,932	8,261
Non-current liabilities		3,279	1,962
Revenue		31,930	28,403	[2]	49,809	[3]
Gross profit		10,862	9,508	[2]	9,898	[3]
Net (income) loss attributable to Aegion Corporation		$ 1,209	$ (1,100)	[2]	$ (1,374)	[3]

[1] Attributed to the country of origin.

[2] Includes activity from our Tite Liner® joint venture in Mexico, which was sold during the fourth quarter of 2019.

[3] Includes activity from our pipe coating and insulation joint venture in Louisiana, which was sold during the third quarter of 2018.