Acquisitions (Narrative) (Detail) $ in Thousands	1 Months Ended			4 Months Ended	6 Months Ended
	Mar. 31, 2015 USD ($)	Jan. 31, 2015 USD ($) territory	Mar. 31, 2014 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2015 USD ($) entity	Jun. 30, 2014 USD ($) entity
Business Acquisition [Line Items]
Cash consideration, net of cash acquired					$ 91,724	$ 29,596
Acquisition related costs					$ 594	$ 648
Number of individual businesses acquired that are not specifically described | entity					5	1
Dunn & Company LLC [Member]
Business Acquisition [Line Items]
Contingent consideration payable period			2 years
Contingent consideration			$ 2,923
Dunn & Company LLC [Member] | Maximum [Member]
Business Acquisition [Line Items]
Contingent consideration payment discount rate			2.70%
Contingent consideration			$ 3,000
Dunn & Company LLC [Member] | Minimum [Member]
Business Acquisition [Line Items]
Contingent consideration payment discount rate			2.40%
Shale Gas [Member]
Business Acquisition [Line Items]
Number of E&P waste stream treatment and recycling operations acquired | territory		2
Cash consideration, net of cash acquired		$ 41,000
Contingent consideration payable period		2 years
Contingent consideration		$ 0
DNCS [Member]
Business Acquisition [Line Items]
Cash consideration, net of cash acquired	$ 30,000
Debt fair value discount rate	4.75%
Long-term note payment period	20 years
Long-term note issued to former owners	$ 5,088
Payment terms					The long-term note requires ten annual principal payments of $500, followed by an additional ten annual principal payments of $250, for total future cash payments of $7,500. The fair value of the long-term note was determined by applying a discount rate of 4.75% to the payments over the 20-year payment period.
Total future cash payments				$ 7,500
DNCS [Member] | First 10 Years [Member]
Business Acquisition [Line Items]
Annual principal payment				500	$ 500
DNCS [Member] | Years 11 Through 20 [Member]
Business Acquisition [Line Items]
Annual principal payment				$ 250	$ 250
Screwbean Landfill, LLC [Member] | Dunn & Company LLC [Member]
Business Acquisition [Line Items]
Cash consideration, net of cash acquired			$ 27,020