Note 2 - Accounting Policies - Investments in Variable Interest Entities (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Current assets		$ 435,580		$ 435,580		$ 450,215
Current liabilities		213,212		213,212		234,041
Revenue	[1]	245,017	$ 318,740	532,392	$ 595,644
Gross profit	[1]	53,575	67,437	103,459	115,732
Net income (loss) attributable to Aegion Corporation		3,856	(8,366)	2,224	(12,367)
Variable Interest Entity, Primary Beneficiary [Member]
Current assets		16,546		16,546		18,304
Non-current assets		7,892		7,892		7,635
Current liabilities		5,764		5,764		8,261
Non-current liabilities		2,521		2,521		$ 1,962
Revenue		5,727	7,519	13,456	13,444
Gross profit		2,078	2,416	4,381	4,051
Net income (loss) attributable to Aegion Corporation		$ 70	$ (652)	$ 355	$ (619)

[1] Revenues and gross profit are attributed to the country of origin