Property and Equipment (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Components of Property, Plant and Equipment
Land	$ 1,442	$ 1,442
Buildings and leasehold improvements	19,263	18,520
Machinery, equipment and rental tools	54,869	54,279
Equipment in progress	10,909	9,382
Furniture and fixtures	1,354	1,358
Property and equipment	99,656	96,860
Less accumulated depreciation	(42,498)	(40,361)
Property and equipment , net	57,158	56,499
Transportation equipment [Member]
Components of Property, Plant and Equipment
Property and equipment	5,479	5,136
Computer equipment and software [Member]
Components of Property, Plant and Equipment
Property and equipment	$ 6,340	$ 6,743