BUSINESS COMBINATION (Details) (USD $)	12 Months Ended		0 Months Ended	12 Months Ended	9 Months Ended	0 Months Ended
	Dec. 31, 2014	Dec. 31, 2012	Jun. 17, 2014	Dec. 31, 2013	Sep. 30, 2014	May 31, 2012
BUSINESS ACQUISITIONS
Payment to acquire business, net of cash acquired	$ 460,874,000	$ 10,743,000
Consideration paid and the fair value of assets acquired and liabilities assumed
Goodwill	217,172,000	23,105,000		21,693,000
Additional information
Goodwill recognized is expected to be deductible for income tax purposes	0
Field & Industrial Services
Consideration paid and the fair value of assets acquired and liabilities assumed
Goodwill	65,100,000
Environmental Services
Consideration paid and the fair value of assets acquired and liabilities assumed
Goodwill	152,100,000
EQ
BUSINESS ACQUISITIONS
Percentage of outstanding shares acquired			100.00%
Payment to acquire business, net of cash acquired			460,900,000
Amount of term loan which was used to funded acquisition			415,000,000
Consideration paid and the fair value of assets acquired and liabilities assumed
Current assets	111,982,000
Property and equipment	101,543,000
Identifiable intangible assets	252,874,000		252,874,000
Current liabilities	(57,585,000)
Other liabilities	(139,331,000)
Total identifiable net assets	269,483,000		269,483,000
Goodwill	197,163,000		197,163,000
Total purchase price	466,646,000		466,646,000
Additional information
Revenue since acquisition included in consolidated statements of operations	228,200,000
Operating income (loss) since acquisition included in consolidated statements of operations	18,500,000
Acquisition-related costs included in selling, general and administrative expenses	6,400,000
Pro forma combined:
Revenue	615,264,000			539,760,000
Net income	37,347,000			29,606,000
Earnings per share - Basic (in dollars per share)	$ 1.73			$ 1.59
Earnings per share - Diluted (in dollars per share)	$ 1.72			$ 1.59
EQ | Previously Reported
Consideration paid and the fair value of assets acquired and liabilities assumed
Current assets					113,199,000
Property and equipment					103,532,000
Identifiable intangible assets					250,900,000
Current liabilities					(57,438,000)
Other liabilities					(131,159,000)
Total identifiable net assets					279,034,000
Goodwill					192,633,000
Total purchase price					471,667,000
EQ | Adjustments
Consideration paid and the fair value of assets acquired and liabilities assumed
Current assets					(1,217,000)
Property and equipment					(1,989,000)
Identifiable intangible assets					1,974,000
Current liabilities					(147,000)
Other liabilities					(8,172,000)
Total identifiable net assets					(9,551,000)
Goodwill					4,530,000
Total purchase price					(5,021,000)
EQ | Environmental Services
Consideration paid and the fair value of assets acquired and liabilities assumed
Goodwill	132,100,000
EQ | Customer relationships
Consideration paid and the fair value of assets acquired and liabilities assumed
Identifiable intangible assets			98,400,000
Additional information
Weighted average amortization period			15 years
EQ | Permits and licenses
Consideration paid and the fair value of assets acquired and liabilities assumed
Identifiable intangible assets			89,600,000
Additional information
Weighted average amortization period			45 years
EQ | Permits and licenses, nonamortizing
Consideration paid and the fair value of assets acquired and liabilities assumed
Identifiable intangible assets			49,000,000
EQ | Tradename
Consideration paid and the fair value of assets acquired and liabilities assumed
Identifiable intangible assets			5,481,000
Additional information
Weighted average amortization period			3 years
EQ | Customer backlog
Consideration paid and the fair value of assets acquired and liabilities assumed
Identifiable intangible assets			4,600,000
Additional information
Weighted average amortization period			10 years
EQ | Developed software
Consideration paid and the fair value of assets acquired and liabilities assumed
Identifiable intangible assets			3,443,000
Additional information
Weighted average amortization period			9 years
EQ | Non-compete agreements
Consideration paid and the fair value of assets acquired and liabilities assumed
Identifiable intangible assets			900,000
Additional information
Weighted average amortization period			1 year
EQ | Internet domain and website
Consideration paid and the fair value of assets acquired and liabilities assumed
Identifiable intangible assets			869,000
Additional information
Weighted average amortization period			19 years
EQ | Database
Consideration paid and the fair value of assets acquired and liabilities assumed
Identifiable intangible assets			581,000
Additional information
Weighted average amortization period			15 years
Dynecol
BUSINESS ACQUISITIONS
Percentage of outstanding shares acquired						100.00%
Consideration paid and the fair value of assets acquired and liabilities assumed
Current assets						2,214,000
Property and equipment						6,552,000
Identifiable intangible assets						1,940,000
Current liabilities						(1,268,000)
Total identifiable net assets						9,438,000
Goodwill						1,327,000
Total purchase price						10,765,000
Additional information
Revenue since acquisition included in consolidated statements of operations		6,700,000
Operating income (loss) since acquisition included in consolidated statements of operations		(161,000)
Acquisition-related costs included in selling, general and administrative expenses		348,000
Number of employees	40
Number of years for which the acquired entity existed	40 years
Amortization period of goodwill recognized and expected to be deductible for income tax purposes	15 years
Pro forma combined:
Revenue		174,639,000
Net income		$ 25,513,000
Earnings per share - Basic (in dollars per share)		$ 1.40
Earnings per share - Diluted (in dollars per share)		$ 1.40