Property, Plant and Equipment (Tables)

12 Months Ended

Dec. 31, 2017

Property, Plant and Equipment

Schedule of property, plant and equipment at cost net of accumulated depreciation

December 31,	2017			2016
(in thousands)
Land	$	19,991		$	19,070
Buildings and leasehold improvements		138,072			142,741
Operating equipment		1,419,670			1,432,007
Computer software		23,017			22,050
Furniture and fixtures		7,656			8,056
Vehicles		494,833			469,570
Construction in progress		—			—
Gross property, plant and equipment		2,103,239			2,093,494
Less: accumulated depreciation		(1,659,311	)		(1,595,508	)
Net property, plant and equipment	$	443,928		$	497,986