Property, Plant and Equipment (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Components of Property, Plant and Equipment
Land	$ 1,456	$ 1,220
Buildings and leasehold improvements	18,443	18,401
Machinery, equipment and rental tools	52,541	44,364
Equipment in progress	5,174	4,048
Furniture and fixtures	1,326	1,288
Property and equipment	90,435	76,074
Less accumulated depreciation	(38,012)	(32,160)
Property and equipment , net	52,423	43,914
Transportation equipment [Member]
Components of Property, Plant and Equipment
Property and equipment	5,318	4,853
Computer equipment and software [Member]
Components of Property, Plant and Equipment
Property and equipment	$ 6,177	$ 1,900