Property and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 153,195		$ 153,195		$ 139,441
Less accumulated depreciation	(97,640)		(97,640)		(94,818)
Property and equipment, net	55,555		55,555		44,623
Total depreciation and amortization	4,284	$ 2,262	$ 7,873	$ 4,674
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
Assets not held under capital leases
Property, Plant and Equipment [Line Items]
Total depreciation and amortization	3,828	2,171	$ 7,172	4,493
Assets held under finance leases
Property, Plant and Equipment [Line Items]
Total depreciation and amortization	456	$ 91	701	$ 181
Tractors and trailers
Property, Plant and Equipment [Line Items]
Property and equipment, gross	106,046		$ 106,046		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
Tractors and trailers | Assets held under finance leases
Property, Plant and Equipment [Line Items]
Property and equipment, gross	5,500		$ 5,500		4,700
Less accumulated depreciation	(1,200)		(1,200)		(700)
Field equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	24,895		$ 24,895		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
Field equipment | Assets held under finance leases
Property, Plant and Equipment [Line Items]
Property and equipment, gross	3,300		$ 3,300
Less accumulated depreciation	(200)		(200)
Buildings
Property, Plant and Equipment [Line Items]
Property and equipment, gross	16,003		$ 16,003		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	1,923		$ 1,923		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		1,790
Construction in progress
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 2,538		$ 2,538		$ 2,794