Property and Equipment

12 Months Ended

Dec. 31, 2017

Property, Plant and Equipment [Abstract]

Property and Equipment

2. Property and Equipment

Property and equipment consisted of the following as of December 31 (in thousands):

	2017			2016
Land	$	3,785		$	3,189
Buildings and leasehold improvements	18,625			18,520
Computer equipment and software	55,793			47,313
Office equipment, furniture, and fixtures	5,035			6,250
Dock, warehouse, and other equipment	9,259			8,852
Tractors and trailers	144,260			147,015
Aircraft fleet and rotable spare parts	29,827			29,171
Property and equipment, gross	266,584			260,310
Less: Accumulated depreciation	(107,037		)	(88,453		)
Property and equipment, net	$	159,547		$	171,857

As of December 31, 2017, $10.9 million of assets not yet placed into service have been included in the line items above. Property and equipment Depreciation expense was $28.5 million, $29.6 million, and $23.2 million for the years ended December 31, 2017, 2016, and 2015, respectively.