Property and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 123,782		$ 123,782		$ 126,276
Less accumulated depreciation, depletion and amortization	(96,478)		(96,478)		(96,914)
Property and equipment, net	27,304		27,304		29,362
Total depreciation, depletion and amortization	2,262	$ 3,563	$ 4,674	$ 7,532
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	83,686		$ 83,686		88,065
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	19,811		$ 19,811		18,490
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			5 years
Buildings
Property, Plant and Equipment [Line Items]
Property and equipment, gross	15,727		$ 15,727		15,727
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	1,808		$ 1,808		1,929
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	960		960		275
Assets not held under capital leases
Property, Plant and Equipment [Line Items]
Total depreciation, depletion and amortization	2,171	3,563	4,493	7,532
Assets held under capital leases
Property, Plant and Equipment [Line Items]
Property and equipment, gross	1,800		1,800		1,800
Less accumulated depreciation, depletion and amortization	(300)		(300)		$ (100)
Total depreciation, depletion and amortization	$ 91	$ 0	$ 181	$ 0