Note 4 - Goodwill and Acquired Intangible Assets (Detail) (USD $)	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Goodwill	$ 249,888,000	[1]	$ 190,120,000	[1],[2]	$ 188,600,000	[2]
Goodwill, Acquired During Period	63,700,000	[3]	1,600,000	[4]
Amortization of Intangible Assets	7,100,000		6,400,000		5,700,000
Insituform-Singapore Subsidiary [Member]
Goodwill, Acquired During Period			1,600,000
Contract Backlog [Member]
Acquired Finite-lived Intangible Asset, Amount	1,600,000
Finite-Lived Intangible Assets, Average Useful Life	1
Scenario, Previously Reported [Member]
Goodwill			182,100,000
Scenario, Actual [Member]
Goodwill			188,600,000
Trademarks and Tradenames [Member]
Acquired Finite-lived Intangible Asset, Amount	6,400,000
Finite-Lived Intangible Assets, Average Useful Life	20
Lease Agreements [Member]
Acquired Finite-lived Intangible Asset, Amount	800,000
Finite-Lived Intangible Assets, Average Useful Life	10
Customer Relationships [Member]
Acquired Finite-lived Intangible Asset, Amount	49,700,000
Finite-Lived Intangible Assets, Average Useful Life	18
Patents and Acquired Technology [Member]
Acquired Finite-lived Intangible Asset, Amount	23,700,000
Finite-Lived Intangible Assets, Average Useful Life	19
CRTS [Member]
Goodwill, Acquired During Period	18,500,000
Hockway [Member]
Goodwill, Acquired During Period	2,000,000
Fyfe NA [Member]
Goodwill, Acquired During Period	$ 43,200,000

[1] The Company does not have any accumulated impairment charges.

[2] During 2011, the Company revised previously reported goodwill balances related to foreign currency translation. As a result of this revision, goodwill as of January 1, 2010 was revised from the previously reported amount of $182.1 million to $188.6 million. See Note 2 for additional information.

[3] During 2011, the Company recorded goodwill of $18.5 million related to the acquisition of CRTS, $2.0 million related to the acquisition of Hockway and $43.2 million related to the acquisition of Fyfe NA as discussed in Note 1.

[4] During 2010, the Company recorded goodwill of $1.6 million related to the acquisition of its licensee in Singapore.