Note 2 - Accounting Policies (Details)	3 Months Ended		24 Months Ended
	Jun. 30, 2013 USD ($)	Jun. 30, 2013 EUR (€)	Jun. 30, 2015 USD ($)	Jun. 30, 2015 GBP (£)	Sep. 30, 2013 USD ($)	Dec. 31, 2012 USD ($)	Sep. 30, 2012 USD ($)	Sep. 30, 2013 Bayou Delta [Member]	Jun. 30, 2013 Insituform-Germany [Member]	Sep. 30, 2013 WCU [Member]	Sep. 30, 2013 Bayou Coating [Member]
Note 2 - Accounting Policies [Line Items]
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax					$ 2,100,000		$ 8,500,000
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax					1,300,000		900,000
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	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
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners										49.00%
Equity Method Investment, Ownership Percentage								41.00%			49.00%
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures					$ 10,920,000	$ 19,181,000