Quarterly Financial Results (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2017		Sep. 30, 2017		Jun. 30, 2017		Mar. 31, 2017		Dec. 31, 2016		Sep. 30, 2016		Jun. 30, 2016		Mar. 31, 2016		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Product sales	$ 13,613		$ 14,169		$ 14,323		$ 14,863		$ 18,611		$ 19,020		$ 20,062		$ 15,382		$ 56,968	$ 73,075	$ 76,213
Service sales	25,365		26,281		26,126		25,348		25,319		26,826		25,904		24,998		103,120	103,047	108,421
Cost of Goods Sold	8,062		9,578		9,295		10,539		11,674		11,001		12,989		10,670		37,474	46,334	47,404
Cost of Services	12,956		13,374		13,094		13,268		13,140		13,576		13,259		12,991		52,692	52,966	54,816
Operating Expenses	19,085		19,299		19,428		20,874		19,384		18,256		20,411		20,093
Operating Income (Loss)	(1,125)		(1,801)		(1,368)		(4,470)		(268)		3,013		(693)		(3,374)		(8,764)	(1,322)	3,208
Net loss	$ (1,685)		$ (2,438)		$ (2,026)		$ (4,885)		$ (6,783)		$ 2,863		$ (806)		$ (2,791)		$ (11,034)	$ (7,517)	$ 2,253
Net (loss) income per share:
Basic (in dollars per share)	$ (0.10)	[1]	$ (0.15)	[1]	$ 0	[1]	$ (0.30)	[1]	$ (0.43)	[1]	$ 0.18	[1]	$ 0	[1]	$ (0.18)	[1]	$ (0.67)	$ (0.47)	$ 0.14
Diluted (in dollars per share)	$ (0.10)	[1]	$ (0.15)	[1]	$ 0	[1]	$ (0.30)	[1]	$ (0.43)	[1]	$ 0.18	[1]	$ 0	[1]	$ (0.18)	[1]	$ (0.67)	$ (0.47)	$ 0.14

[1] Net (loss) income per share is computed independently for each of the quarters. Therefore, the net (loss) income per share for the four quarters may not equal the annual net (loss) income per share data.