Acquisitions (Allocation of Purchase Price) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Mar. 13, 2015	Jan. 13, 2015	Dec. 30, 2014	Oct. 29, 2014	Jul. 07, 2014
Business Acquisition [Line Items]
Goodwill	$ 215,130	$ 82,949
Inspection Oilfield Services (IOS) [Member]
Business Acquisition [Line Items]
Current assets			19,104
Other assets			90
Property, plant and equipment			47,968
Goodwill			123,412
Other intangibles			0
Liabilities assumed			(22,341)
Total			168,233
Tew Holdings, LTD [Member]
Business Acquisition [Line Items]
Current assets				11,957
Other assets				0
Property, plant and equipment				2,398
Goodwill				9,079
Other intangibles				14,048
Liabilities assumed				(6,647)
Total				30,835
Chemtec Energy Services, LLC [Member]
Business Acquisition [Line Items]
Current assets					15,528
Other assets					0
Property, plant and equipment					4,705
Goodwill					22,302
Other intangibles					33,130
Liabilities assumed					(6,756)
Total					68,909
FWO [Member]
Business Acquisition [Line Items]
Current assets						131
Other assets						0
Property, plant and equipment						0
Goodwill						971
Other intangibles						419
Liabilities assumed						(418)
Total						1,103
Carr Concrete [Member]
Business Acquisition [Line Items]
Current assets							3,180
Other assets							45
Property, plant and equipment							7,648
Goodwill							1,936
Other intangibles							1,348
Liabilities assumed							(1,677)
Total							$ 12,480