Note 2 - Accounting Policies (Details)	1 Months Ended						1 Months Ended
	Apr. 30, 2012 USD ($)	Jun. 30, 2013 USD ($)	Dec. 31, 2012 USD ($)	Jun. 30, 2012 USD ($)	Jun. 30, 2013 WCU [Member]	Jun. 30, 2013 Bayou Coating [Member]	Jun. 30, 2013 Insituform-Germany [Member] USD ($)	Jun. 30, 2013 Insituform-Germany [Member] EUR (€)	Jun. 30, 2013 Insituform-Germany [Member] GBP (£)	Jun. 30, 2013 Bayou Delta [Member]	Jun. 30, 2013 Minimum [Member]	Jun. 30, 2013 Maximum [Member]
Note 2 - Accounting Policies (Details) [Line Items]
Number of Components		3
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax		$ 6,000,000		$ 6,500,000
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax		500,000		(800,000)
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net of Tax		200,000		(300,000)
Noncontrolling Interest, Ownership Percentage by Parent							50.00%	50.00%	50.00%
Business Combination, Consideration Transferred (in Euro)	40,144,000						18,300,000	14,000,000
Business Combination, Consideration Transferred	40,144,000						18,300,000	14,000,000
Gain (Loss) on Disposition of Business							11,300,000
Business Acquisition, Transaction Costs							500,000
Long-term Purchase Commitment, Amount (in Pounds)							3,600,000		2,300,000
Long-term Purchase Commitment, Amount							3,600,000		2,300,000
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners					49.00%	49.00%				41.00%
Equity Method Investment, Ownership Percentage											20.00%	50.00%
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures		$ 10,979,000	$ 19,181,000
Number of Steps, VIE		2