Condensed Consolidated Statements of Operations (Unaudited) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Sales and service revenue
Product sales	$ 42,221	$ 39,044	$ 82,386	$ 76,398
Service revenue	27,106	24,304	53,690	47,849
Net sales	69,327	63,348	136,076	124,247
Cost of sales and service revenue
Cost of product sales	29,189	27,857	56,574	54,506
Cost of service revenue	23,171	20,246	46,017	39,938
Cost of sales	52,360	48,103	102,591	94,444
Gross profit	16,967	15,245	33,485	29,803
Selling, general and administrative expenses	8,881	8,523	17,961	17,174
Income from operations	8,086	6,722	15,524	12,629
Other income (expense):
Interest expense	(293)	(131)	(494)	(270)
Other, net	(62)	(572)	107	(547)
Total other expense	(355)	(703)	(387)	(817)
Income before income taxes	7,731	6,019	15,137	11,812
Provision for income taxes	2,626	2,053	5,240	3,577
Net income	$ 5,105	$ 3,966	$ 9,897	$ 8,235
Amounts per common share:
Net income per common share (in dollars per share)	$ 0.44	$ 0.34	$ 0.85	$ 0.71
Net income per common share assuming dilution (in dollars per share)	$ 0.43	$ 0.34	$ 0.84	$ 0.70
Weighted average common shares outstanding (in shares)	11,671,388	11,548,139	11,644,698	11,528,776
Weighted average dilutive common shares outstanding (in shares)	11,833,503	11,747,230	11,809,972	11,721,361