Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Sales:
Net sales	$ 170,761	$ 160,088	$ 176,122
Costs and expenses:
Research and development	14,951	15,858	16,030
Sales, marketing and support	34,910	33,896	33,942
General and administrative	27,964	28,932	28,172
Total costs and expenses	177,925	168,852	177,444
Loss from operations	(7,164)	(8,764)	(1,322)
Interest income	635	659	513
Interest expense	1,793	1,467	1,436
Other income (expense), net	655	(366)	275
Loss before income tax expense	(7,667)	(9,938)	(1,970)
Income tax expense	565	1,096	5,547
Net loss	$ (8,232)	$ (11,034)	$ (7,517)
Earnings per share, basic and diluted (in dollars per share)	$ (0.48)
Per share information:
Net loss per share, basic (in dollars per share)		$ (0.67)	$ (0.47)
Net loss per share, diluted (in dollars per share)	$ (0.48)	$ (0.67)	$ (0.47)
Number of shares used in per share calculation:
Basic (in shares)	17,072	16,419	15,834
Diluted (in shares)	17,072	16,419	15,834
Product
Sales:
Net sales	$ 63,277	$ 56,968	$ 73,075
Costs and expenses:
Cost of product and service sales	39,510	37,474	46,334
Service
Sales:
Net sales	107,484	103,120	103,047
Costs and expenses:
Cost of product and service sales	$ 60,590	$ 52,692	$ 52,966