Property, Plant and Equipment (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Components of Property, Plant and Equipment
Land	$ 1,442	$ 1,220
Buildings and leasehold improvements	18,520	18,401
Machinery, equipment and rental tools	54,279	44,364
Equipment in progress	9,382	4,048
Furniture and fixtures	1,358	1,288
Property and equipment	96,860	76,074
Less accumulated depreciation	(40,361)	(32,160)
Property and equipment, net	56,499	43,914
Transportation equipment [Member]
Components of Property, Plant and Equipment
Property and equipment	5,136	4,853
Computer equipment and software [Member]
Components of Property, Plant and Equipment
Property and equipment	$ 6,743	$ 1,900