Note 1 - General (Detail) (USD $)	Jun. 30, 2011 CRTS Acquisition [Member]	Jun. 30, 2011 Hockway Acquisition [Member]	Jun. 30, 2011 Corrpower Joint Venture [Member]	Jun. 30, 2011 Bayou Wasco Joint Venture [Member]	Jun. 30, 2011 WCU Joint Venture [Member]	Jun. 30, 2011 Bayou Delta Subsidiary [Member]	Jun. 30, 2011 Bayou Coating Investment [Member]	Jan. 29, 2010 Insituform Singapore Subsidiary [Member]
Business Acquisition, Cost of Acquired Entity, Purchase Price (in Dollars)	$ 24,000,000	$ 4,600,000						$ 1,300,000
Business Acquisition, Contingent Consideration, Potential Cash Payment (in Dollars)	15,000,000	1,500,000
Business Acquisition, Contingent Consideration, at Fair Value (in Dollars)	13,900,000
Business Acquisition, Cost of Acquired Entity, Transaction Costs (in Dollars)	$ 300,000
Noncontrolling Interest, Ownership Percentage by Parent			70.00%	51.00%		59.00%
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners			30.00%			41.00%
Equity Method Investment, Ownership Percentage					49.00%		49.00%