SEGMENT REPORTING (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011
Segment reporting information
Third party revenues	$ 572,022	$ 434,962
Intersegment revenues, net
Direct revenues	572,022	434,962
Property, plant and equipment, net	918,684		903,947
Goodwill	125,723		122,392
Permits and other intangibles, net	138,967		139,644
Total assets	2,092,895		2,085,803
Reconciliation to Consolidated Statements of Income:
Reporting segments number	4
Number of operations for which the revenues are insignificant	2
Accretion of environmental liabilities	2,416	2,389
Depreciation and amortization	36,831	25,460
Income from operations	61,701	39,742
Other expense (income)	299	(2,899)
Interest expense, net of interest income	11,272	6,478
Income from continuing operations, before provision for income taxes	50,130	36,163
United States
Segment reporting information
Total assets	1,105,994		1,119,491
Canada
Segment reporting information
Total assets	986,901		961,936
Other foreign
Segment reporting information
Total assets	0		4,376
Reportable segments
Segment reporting information
Adjusted EBITDA, Total	100,948	67,591
Property, plant and equipment, net	918,684		903,947
Total Intangible assets	264,690		262,036
Total assets	2,092,895		2,085,803
Technical Services
Segment reporting information
Third party revenues	209,967	196,016
Intersegment revenues, net	9,554	3,346
Direct revenues	219,521	199,362
Adjusted EBITDA, Total	50,825	47,679
Property, plant and equipment, net	307,005		308,118
Goodwill	44,452		44,410
Permits and other intangibles, net	80,983		81,605
Total Intangible assets	125,435		126,015
Total assets	601,864		604,904
Field Services
Segment reporting information
Third party revenues	51,810	51,691
Intersegment revenues, net	(4,293)	(2,157)
Direct revenues	47,517	49,534
Adjusted EBITDA, Total	2,304	3,989
Property, plant and equipment, net	32,126		30,296
Goodwill	2,232		2,232
Permits and other intangibles, net	1,167		1,204
Total Intangible assets	3,399		3,436
Total assets	39,439		37,850
Industrial Services
Segment reporting information
Third party revenues	160,096	112,882
Intersegment revenues, net	(7,536)	(3,479)
Direct revenues	152,560	109,403
Adjusted EBITDA, Total	34,657	24,296
Property, plant and equipment, net	264,923		254,469
Goodwill	46,143		45,444
Permits and other intangibles, net	20,292		19,701
Total Intangible assets	66,435		65,145
Total assets	350,142		345,202
Oil and Gas Field Services
Segment reporting information
Third party revenues	149,448	74,334
Intersegment revenues, net	2,548	2,800
Direct revenues	151,996	77,134
Adjusted EBITDA, Total	38,399	13,712
Property, plant and equipment, net	268,521		267,987
Goodwill	32,896		30,306
Permits and other intangibles, net	36,525		37,134
Total Intangible assets	69,421		67,440
Total assets	425,991		429,938
Corporate Items
Segment reporting information
Third party revenues	701	39
Intersegment revenues, net	(273)	(510)
Direct revenues	428	(471)
Adjusted EBITDA, Total	(25,237)	(22,085)
Property, plant and equipment, net	46,109		43,077
Total assets	$ 675,459		$ 667,909