Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net income (loss)	$ (66,235)	$ 29,160	$ (7,990)
Adjustments to reconcile to net cash provided by operating activities:
Depreciation and amortization	44,419	46,719	43,791
Gain on sale of fixed assets	(59)	(1,916)	(929)
Equity-based compensation expense	11,162	9,261	7,987
Deferred income taxes	(9,376)	1,772	924
Non-cash restructuring charges	10,080	300	1,816
Non-cash portion of litigation settlement	0	(3,000)	0
Definite-lived intangible asset impairment	41,032	0	0
Goodwill impairment	45,390	0	43,484
Debt issuance costs	0	0	3,377
Loss on sale of businesses	0	0	3,414
Loss on foreign currency transactions	2,152	911	80
Other	(1,562)	(1,044)	(168)
Changes in operating assets and liabilities (net of acquisitions):
Restricted cash related to operating activities	1,258	2,055	(382)
Receivables net, retainage and costs and estimated earnings in excess of billings	(29,847)	52,774	12,283
Inventories	(1,926)	(2,569)	6,984
Prepaid expenses and other assets	8,732	16,759	(28,895)
Accounts payable and accrued expenses	18,803	(49,259)	(582)
Billings in excess of costs and estimated earnings	(5,924)	(27,761)	45,700
Other operating	(1,798)	(946)	1,129
Net cash provided by operating activities	66,301	73,216	132,023
Cash flows from investing activities:
Capital expenditures	(30,830)	(38,760)	(29,454)
Proceeds from sale of fixed assets	707	3,310	3,173
Patent expenditures	(379)	(1,043)	(1,503)
Restricted cash related to investing activities	2,000	(1,086)	(3,538)
Purchase of Underground Solutions, Inc., net of cash acquired	0	(84,740)	0
Other acquisition activity, net of cash acquired	(9,045)	(11,567)	(6,662)
Sale of interest in Bayou Perma-Pipe Canada, Ltd., net of cash disposed	0	6,599	0
Payment to Fyfe Asia sellers for final net working capital	0	0	(1,098)
Net cash used in investing activities	(37,547)	(127,287)	(39,082)
Cash flows from financing activities:
Proceeds from issuance of common stock upon stock option exercises, including tax effects	823	1,818	2,466
Repurchase of common stock	(37,849)	(44,454)	(27,804)
Investments from non-controlling interest	158	0	0
Sale of non-controlling interest	0	0	239
Purchase of or distributions to non-controlling interests	(71)	(1,276)	(472)
Payment of contingent consideration	(500)	(500)	(684)
Credit facility financing fees	0	0	(4,360)
Proceeds from (payments on) notes payable, net	639	0	(370)
Proceeds from (payments on) line of credit, net	2,000	36,000	(45,500)
Proceeds from long-term debt	0	0	350,000
Principal payments on long-term debt	(21,647)	(17,500)	(323,750)
Net cash used in financing activities	(56,447)	(25,912)	(50,235)
Effect of exchange rate changes on cash	4,899	(2,213)	(5,975)
Net increase (decrease) in cash and cash equivalents for the year	(22,794)	(82,196)	36,731
Cash and cash equivalents, beginning of year	129,500	211,696	174,965
Cash and cash equivalents, end of year	106,706	129,500	211,696
Cash and cash equivalents associated with assets held for sale, end of year	(989)	0	(2,443)
Cash and cash equivalents, end of year	105,717	129,500	209,253
Supplemental disclosures of cash flow information:
Interest	14,998	11,118	9,873
Income taxes	$ 5,649	$ (517)	$ 8,753