Property, Plant and Equipment (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Components of Property, Plant and Equipment
Land	$ 1,452	$ 1,220
Buildings and leasehold improvements	18,588	18,401
Machinery, equipment and rental tools	51,766	44,364
Equipment in progress	4,679	4,048
Furniture and fixtures	1,327	1,288
Property, plant and equipment	85,067	76,074
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	(36,149)	(32,160)
Property, plant and equipment , net	48,918	43,914
Transportation Equipment [Member]
Components of Property, Plant and Equipment
Property, plant and equipment	5,314	4,853
Computer Equipment [Member]
Components of Property, Plant and Equipment
Property, plant and equipment	$ 1,941	$ 1,900