Property and Equipment (Tables)

3 Months Ended

Mar. 31, 2018

Property, Plant and Equipment [Abstract]

Property and equipment

Components of depreciation, depletion and amortization expense were as follows for the periods indicated (in thousands):

	Three Months Ended
	March 31,
	2018		2017
Depreciation, depletion and amortization, excluding amounts
under capital leases	$	2,322	$	3,969
Amortization of property and equipment under capital leases	90		—
Total depreciation, depletion and amortization	$	2,412	$	3,969

The historical costs of our property and equipment and related accumulated depreciation balances were as follows at the dates indicated (in thousands):

	Estimated
	Useful Life	March 31,			December 31,
	in Years	2018			2017
Tractors and trailers (1)	5 – 6	$	86,492		$	88,065
Field equipment	2 – 5	18,827			18,490
Buildings	5 – 39	15,728			15,727
Office equipment	1 – 5	1,831			1,929
Land		1,790			1,790
Construction in progress		761			275
Total		125,429			126,276
Less accumulated depreciation		(97,685		)	(96,914		)
Property and equipment, net		$	27,744		$	29,362

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(1) Amounts include assets held under capital leases for certain tractors in our marketing segment. Gross property and equipment associated with assets held under capital leases were $1.8 million and $1.8 million at March 31, 2018 and December 31, 2017, respectively. Accumulated amortization associated with assets held under capital leases were $0.2 million and $0.1 million at March 31, 2018 and December 31, 2017, respectively (see Note 11 for further information).