Accounting Policies - VIE Income Statement (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Accounting Policies [Abstract]
Revenue	$ 16,405	$ 11,457	$ 39,179	$ 72,916
Gross profit	3,238	1,984	6,982	11,704
Net income (loss) attributable to Aegion Corporation	$ (946)	$ 1,121	$ (886)	$ 3,071