Note 1 - General (Details)	3 Months Ended			6 Months Ended		12 Months Ended	24 Months Ended		3 Months Ended			6 Months Ended		3 Months Ended
	Jun. 30, 2014 USD ($)	Jun. 30, 2013 USD ($)	Jun. 30, 2013 EUR (€)	Jun. 30, 2014 USD ($)	Jun. 30, 2013 USD ($)	Dec. 31, 2013 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2015 GBP (£)	Jun. 30, 2013 Goodwill and Intagible Assets [Member] USD ($)	Jun. 30, 2013 Tangible Assets [Member] USD ($)	Jun. 30, 2013 Brinderson LP [Member] USD ($)	Jun. 30, 2014 Brinderson LP [Member] USD ($)	Jul. 02, 2013 Brinderson LP [Member] USD ($)	Jun. 30, 2014 Bayou Coating [Member] USD ($)	Jun. 30, 2013 Bayou Coating [Member] USD ($)	Mar. 31, 2014 Bayou Coating [Member]	Dec. 31, 2013 Bayou Coating [Member]	Jun. 30, 2014 Delta Double Jointing [Member]	Jun. 30, 2014 Brinderson LP [Member] USD ($)	Jul. 02, 2013 2013 Credit Facility [Member] USD ($)	Jun. 30, 2013 Insituform Germany [Member]
General [Line Items]
Goodwill, Acquired During Period				$ 1,100,000
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net													150,000,000
Debt Instrument, Face Amount																				650,000,000
Goodwill and Intangible Asset Impairment		3,900,000
Goodwill and Intangible Asset Impairment, Net of Tax		2,400,000
Impairment Effect on Earnings Per Share, after Tax (in Dollars per share)									$ 0.06	$ 0.02
Tangible Asset Impairment Charges		1,100,000
Tangible Asset Impairment Charges, Net of Tax		700,000
Business Exit Costs						100,000
Noncontrolling Interest, Ownership Percentage by Parent																		59.00%			50.00%
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners														51.00%				41.00%
Sale of interests in German joint venture				9,065,000	0
Payments to Noncontrolling Interests				617,000	0
PercentOfBookValue																49.00%	49.00%
Gain (Loss) on Sale of Equity Investments				(472,000)	0
Equity Method Investment, Other than Temporary Impairment															2,700,000
Equity Method Investment Other Than Temporary Impairment Net Of Tax															1,800,000
Total consideration recorded		18,300,000	14,000,000	0	(18,300,000)						147,600,000	147,605,000
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
Equity in earnings of affiliated companies	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
Loss Contingency Accrual																			$ 14,500,000