Acquisitions (Narrative) (Details) - USD ($) $ in Thousands						3 Months Ended	6 Months Ended
	Mar. 13, 2015	Jan. 13, 2015	Dec. 30, 2014	Oct. 29, 2014	Jul. 07, 2014	Jun. 30, 2015	Jun. 30, 2015	Jun. 30, 2014
Business Acquisition [Line Items]
Payments to Acquire Businesses, Net of Cash Acquired							$ 193,871	$ 495
Acquisition related costs						$ 225	$ 595
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.
Payments to Acquire Businesses, Net of Cash Acquired	$ 167,404
Working capital adjustment	2,363
Earn out provision proceeds	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