Accounting Policies - VIE Income Statement (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Accounting Policies [Abstract]
Revenue	$ 6,723	$ 27,398	$ 22,773	$ 61,459
Gross profit	434	4,190	3,744	9,720
Net income (loss) attributable to Aegion Corporation	$ (1,188)	$ 678	$ 60	$ 1,950