Property and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 144,263		$ 139,441
Less accumulated depreciation	(95,346)		(94,818)
Property and equipment, net	48,917		44,623
Total depreciation and amortization	$ 3,589	$ 2,412
Minimum
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	2 years
Maximum
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	39 years
Tractors and trailers
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 101,470		96,523
Tractors and trailers | Minimum
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	5 years
Tractors and trailers | Maximum
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	6 years
Field equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 21,378		20,725
Field equipment | Minimum
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	2 years
Field equipment | Maximum
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	20 years
Buildings
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 15,821		15,746
Buildings | Minimum
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	5 years
Buildings | Maximum
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	39 years
Office equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 1,886		1,863
Office equipment | Minimum
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	2 years
Office equipment | Maximum
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	5 years
Land
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 1,790		1,790
Construction in progress
Property, Plant and Equipment [Line Items]
Property and equipment, gross	1,918		2,794
Assets Held Under Finance Leases
Property, Plant and Equipment [Line Items]
Property and equipment, gross	5,300
Less accumulated depreciation	(900)
Total depreciation and amortization	245
Assets held under capital leases
Property, Plant and Equipment [Line Items]
Property and equipment, gross			4,700
Less accumulated depreciation			$ (700)
Total depreciation and amortization		90
Assets not held under capital leases
Property, Plant and Equipment [Line Items]
Total depreciation and amortization	$ 3,344	$ 2,322