Document And Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2018	Feb. 25, 2019	Jun. 30, 2018
Document and Entity Information [Abstract]
Entity Registrant Name	Aegion Corp
Document Type	10-K
Current Fiscal Year End Date	--12-31
Entity Public Float			$ 831,818,679
Entity Common Stock, Shares Outstanding (in shares)		31,781,352
Amendment Flag	false
Entity Central Index Key	0000353020
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
Entity Well-known Seasoned Issuer	No
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY