Summary of Significant Accounting Policies - New Accounting Pronouncements (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Change in Contract with Customer, Liability [Abstract]
Beginning balance		$ 1,812	$ 1,057
Deferred revenues added		146	220
Elimination of deferred revenues due to joint venture liquidation		(986)	0
Previously deferred revenues recognized		(123)	(109)
Ending balance		849	1,168
Revenues	[1]	7,837	7,703
Net loss		$ (1,379)	$ (1,261)
Basic and diluted net loss per share (usd per share)		$ (0.30)	$ (0.28)
Accounts receivable, net		$ 2,556		$ 2,296
Deferred cost of revenues		529		1,039
Deferred revenues		849		1,812
Total stockholders’ equity		$ 22,611		23,727
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Change in Contract with Customer, Liability [Abstract]
Revenues			$ 7,799
Net loss			$ (1,199)
Basic and diluted net loss per share (usd per share)			$ (0.27)
Accounts receivable, net				2,721
Deferred cost of revenues				1,767
Deferred revenues				4,805
Total stockholders’ equity				21,887
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Change in Contract with Customer, Liability [Abstract]
Revenues			$ (96)
Net loss			$ (62)
Basic and diluted net loss per share (usd per share)			$ (0.01)
Accounts receivable, net				(425)
Deferred cost of revenues				(728)
Deferred revenues				(2,993)
Total stockholders’ equity				$ 1,840

[1] Represents the portfolio of available for sale securities that is included in restricted investments and short-term investments in the Company’s condensed consolidated balance sheets