Property, Plant and Equipment (Tables)

12 Months Ended

Dec. 31, 2018

Property, Plant and Equipment

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

December 31,	2018			2017
(in thousands)
Land	$	21,159		$	19,991
Buildings and leasehold improvements		140,269			138,072
Operating equipment		1,429,906			1,419,670
Computer software		24,619			23,017
Furniture and fixtures		7,606			7,656
Vehicles		528,250			494,833
Gross property, plant and equipment		2,151,809			2,103,239
Less: accumulated depreciation		(1,633,827	)		(1,659,311	)
Net property, plant and equipment	$	517,982		$	443,928