Acquisitions (Narrative) (Details) - USD ($) $ in Thousands						9 Months Ended
	Mar. 13, 2015	Jan. 13, 2015	Dec. 30, 2014	Oct. 29, 2014	Jul. 07, 2014	Sep. 30, 2015	Sep. 30, 2014
Business Acquisition [Line Items]
Payments to Acquire Businesses, Net of Cash Acquired						$ 193,871	$ 12,786
Inspection Oilfield Services (IOS) [Member]
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition	Mar. 13, 2015
Business Acquisition, Name of Acquired Entity	IOS Holdings, Inc. ("IOS")
Payments to Acquire Businesses, Net of Cash Acquired	$ 167,404
Working capital adjustment	2,363
Earn out provision	60,000
Business Combination, Indemnification Assets, Amount as of Acquisition Date	7,600
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net	$ 168,704
Tew Holdings, LTD [Member]
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition		Jan. 13, 2015
Business Acquisition, Name of Acquired Entity		Tew Holdings, LTD ("Tew")
Payments to Acquire Businesses, Net of Cash Acquired		$ 26,467
Working capital adjustment		4,200
Business Combination, Indemnification Assets, Amount as of Acquisition Date		600
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net		$ 30,878
Chemtec Energy Services, LLC [Member]
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition			Dec. 30, 2014
Business Acquisition, Name of Acquired Entity			Chemtec Energy Services, L.L.C. ("Chemtec")
Payments to Acquire Businesses, Net of Cash Acquired			$ 66,719
Working capital adjustment			1,867
Business Combination, Indemnification Assets, Amount as of Acquisition Date			5,000
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net			$ 68,909
FWO [Member]
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition				Oct. 29, 2014
Business Acquisition, Name of Acquired Entity				FWO
Payments to Acquire Businesses, Net of Cash Acquired				$ 1,103
Working capital adjustment				161
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net				$ 1,103
Carr Concrete [Member]
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition					Jul. 07, 2014
Business Acquisition, Name of Acquired Entity					Carr Concrete Corporation ("Carr")
Payments to Acquire Businesses, Net of Cash Acquired					$ 12,480
Working capital adjustment					189
Business Combination, Indemnification Assets, Amount as of Acquisition Date					1,000
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net					$ 12,480