Note 2 - Accounting Policies (Details)	3 Months Ended			6 Months Ended		24 Months Ended								3 Months Ended
	Jun. 30, 2014 USD ($)	Jun. 30, 2013 USD ($)	Jun. 30, 2013 EUR (€)	Jun. 30, 2014 USD ($)	Jun. 30, 2013 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2015 GBP (£)	Dec. 31, 2013 USD ($)	Jun. 30, 2014 Minimum [Member]	Jun. 30, 2014 Maximum [Member]	Jun. 30, 2013 Insituform Germany [Member]	Jun. 30, 2014 WCU [Member]	Jun. 30, 2014 Delta Double Jointing [Member]	Jun. 30, 2014 Bayou Coating [Member] USD ($)	Jun. 30, 2013 Bayou Coating [Member] USD ($)	Mar. 31, 2014 Bayou Coating [Member]	Dec. 31, 2013 Bayou Coating [Member]
Note 2 - Accounting Policies [Line Items]
PercentOfBookValue																49.00%	49.00%
Sale of interests in German joint venture				$ 9,065,000	$ 0
Equity Method Investment, Other than Temporary Impairment															2,700,000
Equity Method Investment Other Than Temporary Impairment Net Of Tax															1,800,000
Equity Method Investment, Summarized Financial Information, Net Income (Loss)	0	1,310,000		677,000	2,212,000									1,200,000
Proceeds from Equity Method Investment, Dividends or Distributions				684,000	2,269,000
Gain (Loss) on Sale of Equity Investments				(472,000)	0
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax	2,500,000	6,000,000		2,500,000	6,000,000
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax	(800,000)	(500,000)		(800,000)	(500,000)
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net of Tax	(200,000)	(200,000)		(200,000)	(200,000)
Noncontrolling Interest, Ownership Percentage by Parent											50.00%		59.00%
Total consideration recorded		18,300,000	14,000,000	0	(18,300,000)
Gain (Loss) on Disposition of Business		11,300,000		0	11,771,000
Business Acquisition, Transaction Costs		500,000			500,000
Long-term Purchase Commitment, Amount (in Pounds)						3,600,000	2,300,000
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners												49.00%	41.00%	51.00%
Payments to Noncontrolling Interests				617,000	0
Equity Method Investment, Ownership Percentage									20.00%	50.00%
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	$ 0			$ 0				$ 9,101,000