Reduction in Value of Assets (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended			12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Asset Impairment Charges [Line Items]
Retirments of long-lived assets						$ 26,102
Reduction in value of long-lived assets				$ 70,887	$ 14,155	143,803
Reduction in value of goodwill				668,838		330,500
Reduction in value of assets	$ 739,725	$ 4,202	$ 9,953	739,725	14,155	500,405
Reduction in value of assets related to sale of a business				2,600
Drilling Products And Services [Member]
Asset Impairment Charges [Line Items]
Retirments of long-lived assets						26,100
Reduction in value of assets					1,356	48,903
Impairment of Property, Plant and Equipment						25,000
Technical Solutions [Member]
Asset Impairment Charges [Line Items]
Reduction in value of long-lived assets					8,100
Reduction in value of assets					8,115	25,600
Impairment of Property, Plant and Equipment					25,600
Production Services [Member]
Asset Impairment Charges [Line Items]
Reduction in value of goodwill				85,288		190,500
Reduction in value of assets				92,252		235,067
Impairment of Intangible Assets (Excluding Goodwill)				1,900		21,000
Impairment of Property, Plant and Equipment				5,100		21,400
Onshore Completion And Workover Services [Member]
Asset Impairment Charges [Line Items]
Reduction in value of long-lived assets					6,100
Reduction in value of goodwill				583,550		140,000
Reduction in value of assets				644,813	$ 4,684	190,835
Impairment of Intangible Assets (Excluding Goodwill)				19,800		45,900
Impairment of Property, Plant and Equipment				$ 41,400		$ 4,900