BUSINESS COMBINATIONS (Details)	3 Months Ended		12 Months Ended							1 Months Ended	3 Months Ended		12 Months Ended
	Dec. 31, 2011 Other Acquisitions USD ($)		Dec. 31, 2011 Other Acquisitions USD ($)		Dec. 31, 2010 Other Acquisitions USD ($)	Sep. 30, 2011 Other Acquisitions USD ($)	Dec. 31, 2011 Other Acquisitions Oil and Gas Field Services USD ($)	Dec. 31, 2011 Other Acquisitions Technical Services [Member] USD ($)	Dec. 31, 2011 Other Acquisitions Industrial Services USD ($)	Jun. 30, 2011 Peak Energy Services Ltd.'s ('Peak') USD ($) persons	Dec. 31, 2011 Peak Energy Services Ltd.'s ('Peak') USD ($)		Dec. 31, 2011 Peak Energy Services Ltd.'s ('Peak') USD ($)		Dec. 31, 2010 Peak Energy Services Ltd.'s ('Peak') USD ($)	Jun. 10, 2011 Peak Energy Services Ltd.'s ('Peak') USD ($) TermLoanFacilities		Jun. 10, 2011 Peak Energy Services Ltd.'s ('Peak') CAD	Dec. 31, 2011 Peak Energy Services Ltd.'s ('Peak') Oil and Gas Field Services USD ($)	Dec. 31, 2011 Peak Energy Services Ltd.'s ('Peak') Industrial Services USD ($)	Sep. 30, 2011 Badger Daylighting Ltd. ("Badger") USD ($)	Jan. 25, 2011 Badger Daylighting Ltd. ("Badger") CAD
Summary of consideration paid at the acquisition date
Cash Consideration	$ 112,450,000		$ 112,450,000													$ 162,585,000
Fair value of previously owned common shares																4,117,000	[1]
Net debt assumed	25,183,000		25,183,000													38,431,000	[2]	37,500,000
Estimated net amount due to the sellers for working capital adjustments	3,694,000		3,694,000
Total consideration for acquisition	141,327,000		141,327,000								205,133,000		205,133,000			205,133,000		200,200,000
Outstanding common shares acquired (as a percent)																100.00%		100.00%
Percentage of outstanding common shares of acquiree already owned by company (as a percent)											3.15%		3.15%			3.15%		3.15%
Gain loss recognized in other income previously held as common shares										1,900,000
Fair value of common shares in acquiree																4,100,000
Cash assumed for repayment of outstanding debt																15,700,000
Number of term loan facilities																3		3
Cash paid in exchange for acquisition																158,700,000
Cash paid per share in exchange for acquisition (in dollars per share)																$ 0.95
Exchange rate translation																0.976057		0.976057
Number of employees										900
Summary of Recognised Amounts of Identifiable Assets and Liabilities Assumed [Roll Forward]
Current assets	40,028,000	[3]									44,986,000	[4]
Property, plant and equipment	60,109,000										150,265,000
Identifiable intangible assets	23,371,000										13,186,000
Other assets	196,000										1,109,000
Current liabilities	(19,522,000)										(28,360,000)
Asset retirement obligations	(193,000)										(103,000)
Other liabilities	(4,469,000)										(8,126,000)
Total identifiable net assets	99,520,000										172,957,000
Goodwill	44,637,000	[5]					13,200,000	10,200,000	13,900,000		32,176,000	[6]							8,200,000	16,000,000
Total	144,157,000										205,133,000					205,133,000		200,200,000
Current assets, Measurement Period Adjustments	1,357,000	[3]									1,557,000	[4]
Property, plant, and equipment, Measurement Period Adjustments	2,857,000										1,309,000
Customer relationships and other intangibles, , Measurement Period Adjustments	0										0
Other assets, Measurement Period Adjustments	1,602,000										5,822,000
Current liabilities, Measurement Period Adjustments	(3,039,000)										(676,000)
Asset retirement obligations, Measurement Period Adjustments	(7,000)										0
Other liabilities, Measurement Period Adjustments	1,728,000										(49,000)
Total identifiable net assets, Measurement Period Adjustments	4,498,000										7,963,000
Goodwill, Measurement Period Adjustments	(7,328,000)	[5]									(7,963,000)	[6]
Total, Measurement Period Adjustments	(2,830,000)										0
Current assets, (As adjusted)	41,385,000	[3]	41,385,000	[3]							46,543,000	[4]	46,543,000	[4]
Property, plant and equipment, (As adjusted)	62,966,000		62,966,000								151,574,000		151,574,000
Identifiable intangible assets ( As adjusted)	23,371,000		23,371,000								13,186,000		13,186,000
Other assets (As adjusted)	1,798,000		1,798,000								6,931,000		6,931,000
Current liabilities (As adjusted)	(22,561,000)		(22,561,000)								(29,036,000)		(29,036,000)
Asset retirement obligations (As adjusted)	(200,000)		(200,000)								(103,000)		(103,000)
Other liabilities (As adjusted)	(2,741,000)		(2,741,000)								(8,175,000)		(8,175,000)
Total identifiable net assets	104,018,000		104,018,000								180,920,000		180,920,000
Goodwill (As adjusted)	37,309,000	[5]	37,309,000	[5]			13,200,000	10,200,000	13,900,000		24,213,000	[6]	24,213,000	[6]					8,200,000	16,000,000
Total (As adjusted)	141,327,000		141,327,000								205,133,000		205,133,000			205,133,000		200,200,000
Business Combination, Acquired Receivables, Fair Value						21,400,000					33,300,000		33,300,000
Customer receivables, gross amount due						22,100,000					34,700,000		34,700,000
Acquisition related costs			800,000										700,000
Revenues attributable to acquiree, included in the Company's consolidated statements of income			56,000,000										125,300,000
Unaudited pro forma combined summary data
Pro forma combined revenues			2,091,102,000		1,892,906,000								2,079,329,000		1,879,749,000
Pro forma combined net income			129,106,000		138,549,000								129,103,000		128,481,000
Minimum Affirmative Percentage of Acquirees Shareholders Vote Required for Acquisition Approval																						66.6667%
Maximum amount of obligation of acquiree to reimburse the out of pocket expenses incurred																						1,500,000
Reimbursement received from acquiree																					$ 1,100,000

[1] The Company previously owned a 3.15% interest in Peak which was recorded in marketable securities. On June 10, 2011, the Company acquired the remaining outstanding shares of Peak and as a result, the Company remeasured the fair value of its previously held common shares and recognized the resulting gain of $1.9 million in other income. The unrealized gain on the Peak investment was previously recorded in accumulated other comprehensive income. For this purpose, the fair value of the Company’s previous investment in Peak was deemed to be $4.1 million, calculated based on the closing price of Peak’s shares on the Toronto Stock Exchange on the date before the acquisition was publicly announced.

[2] The outstanding Peak debt, net of $15.7 million of cash assumed, which consisted of three term loan facilities, was paid off on June 10, 2011.

[3] (i)The preliminary fair value of the financial assets acquired includes customer receivables with a preliminary aggregate fair value of $21.4 million. Combined gross amounts due were $22.1 million.

[4] The preliminary fair value of the financial assets acquired includes customer receivables with a preliminary fair value of $33.3 million. The gross amount due was $34.7 million.

[5] (ii)Goodwill represents the excess of the fair value of the net assets acquired over the purchase price. Goodwill of $13.2 million, $10.2 million and $13.9 million has been assigned to the Oil and Gas Field Services segment, the Technical Services segment, and the Industrial Services segment, respectively. Certain amounts will not be deductible for tax purposes.

[6] Goodwill, which is attributable to expected operating and cross-selling synergies, will not be deductible for tax purposes. Goodwill of $8.2 million and $16.0 million has been recorded in the Oil and Gas Field Services and Industrial Services segments, respectively; however, the amount and the allocation are subject to change pending the finalization of the Company’s valuation.