Acquisitions (Narrative) (Details) - USD ($) $ in Thousands				6 Months Ended
	Nov. 23, 2015	Mar. 13, 2015	Jan. 13, 2015	Jun. 30, 2016	Jun. 30, 2015
Business Acquisition [Line Items]
Payments to Acquire Businesses, Net of Cash Acquired				$ 0	$ 193,871
TEW Plus LTD [Member]
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition	Nov. 23, 2015
Business Acquisition, Percentage of Voting Interests Acquired	75.00%
Business Acquisition, Name of Acquired Entity	TEW Plus, LTD ("Tew Plus")
Payments to Acquire Businesses, Net of Cash Acquired	$ 2,130
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" or "test and inspection services")
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
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