Description of Business - Acquisitions/Strategic Initiatives/Divestitures (Details) $ in Thousands, € in Millions, £ in Millions, NZD in Millions												1 Months Ended		3 Months Ended		12 Months Ended
	Mar. 01, 2017 GBP (£)	Mar. 01, 2017 USD ($)	Jul. 01, 2016 NZD company	Jul. 01, 2016 USD ($) company	Jun. 02, 2016 EUR (€)	Jun. 02, 2016 USD ($)	May 13, 2016 USD ($) country	Feb. 18, 2016 USD ($)	Feb. 01, 2016 USD ($)	Mar. 01, 2015 NZD	Mar. 01, 2015 USD ($)	Jul. 31, 2015 USD ($)	Feb. 28, 2015 USD ($)	Mar. 31, 2017 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2017 USD ($) country	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2017	Mar. 01, 2017 USD ($)
Business Acquisition [Line Items]
Number of countries in which entity operates | country																80
Payment of contingent consideration															$ 500	$ 500	$ 500	$ 684
CSL and BCS
Business Acquisition [Line Items]
Total consideration recorded			NZD 8.9	$ 6,400
Number of businesses acquired | company			2	2
Payments to acquire businesses			NZD 7.5	$ 5,500
Milestone payments			NZD 2.0	$ 1,400
LMJ
Business Acquisition [Line Items]
Total consideration recorded					€ 2.9	$ 3,235
Fyfe Europe
Business Acquisition [Line Items]
Total consideration recorded							$ 3,000
Payments to acquire businesses							$ 2,800
Number of countries in which entity operates | country							72
Underground Solutions
Business Acquisition [Line Items]
Total consideration recorded								$ 88,370
Payments to acquire businesses								85,000
Discounted value of net operating loss tax assets								5,000
Consideration transferred, funds held in escrow								6,300
Foreign earnings repatriated								29,700
Foreign earnings repatriated, tax impact								$ 3,200
CRTS
Business Acquisition [Line Items]
Proceeds from settlement of escrow claims												$ 700
Payment of contingent consideration												$ 1,000
Schultz
Business Acquisition [Line Items]
Total consideration recorded										NZD 6.7	$ 7,662
Payments to acquire businesses | NZD										NZD 7.1
Payment of contingent consideration														$ 500
Environmental Techniques
Business Acquisition [Line Items]
Total consideration recorded	£ 6.5	$ 8,046
Escrow deposit	£ 1.0																			$ 1,200
Bayou Perma-Pipe Canada, Ltd
Business Acquisition [Line Items]
Ownership percentage by parent									51.00%
Consideration received									$ 9,600
Proceeds from divestiture of businesses									7,600
Disposal group note receivable									$ 2,000
Video Injection - Instituform SAS
Business Acquisition [Line Items]
Long-term purchase commitment period													5 years
Aegion South Africa Proprietary Limited [Member]
Business Acquisition [Line Items]
Ownership percentage by parent																			60.00%
Ownership percentage by noncontrolling owners																			40.00%
Video Injection - Instituform SAS
Business Acquisition [Line Items]
Gain (loss) on disposition of business													$ (2,900)
Disposed of by Sale | Bayou Perma-Pipe Canada, Ltd
Business Acquisition [Line Items]
Expected loss from disposal, before tax																		600
Operating expenses | CRTS
Business Acquisition [Line Items]
Proceeds from settlement of escrow claims																		200
Other Operating Income (Expense) | CRTS
Business Acquisition [Line Items]
Proceeds from settlement of escrow claims																		$ 800