Property, Plant and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment
Property, plant and equipment, gross	$ 13,929,857	$ 13,556,735
Less: accumulated depreciation and amortization	(7,820,292)	(7,289,152)
Property, Plant and Equipment, Net, Total	6,109,565	6,267,583	$ 7,027,802
Depreciation	835,900	885,400	951,400
Repair and maintenance expense	241,400	151,400	304,700
Interest costs capitalized	2,500	6,700	$ 20,400
Land
Property, Plant and Equipment
Property, plant and equipment, gross	52,000	46,319
Buildings
Property, Plant and Equipment
Property, plant and equipment, gross	134,318	115,502
Drilling, workover and well-servicing rigs, and related equipment
Property, Plant and Equipment
Property, plant and equipment, gross	12,997,470	12,638,749
Marine Transportation and Supply Vessels
Property, Plant and Equipment
Property, plant and equipment, gross	4,377
Oilfield Hauling and Mobile Equipment
Property, Plant and Equipment
Property, plant and equipment, gross	272,384	274,137
Other Machinery and Equipment
Property, Plant and Equipment
Property, plant and equipment, gross	172,674	181,069
Oil and Gas Properties
Property, Plant and Equipment
Property, plant and equipment, gross	12,286	12,286
Construction in Progress
Property, Plant and Equipment
Property, plant and equipment, gross	$ 284,348	$ 288,673