Summary of Significant Accounting Policies - Recently Issued Accounting Pronouncements (Details) - USD ($)		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
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue		$ 8,030,000	$ 7,817,000	$ 8,021,000	$ 7,799,000	$ 7,498,000	$ 8,179,000	$ 8,061,000	$ 8,647,000	$ 31,667,000	[1]	$ 32,385,000	[1]
Net loss		(1,202,000)	(852,000)	(1,370,000)	(1,199,000)	(1,237,000)	(1,228,000)	(763,000)	(875,000)	$ (4,623,000)		$ (4,103,000)
Basic and diluted net loss per share										$ (1.04)		$ (0.93)
Accounts receivable, net	[2]	(2,721,000)				(3,015,000)				$ (2,721,000)		$ (3,015,000)
Deferred cost of goods sold		1,767,000				1,104,000				1,767,000		1,104,000
Accrued liabilities		1,878,000				2,174,000				1,878,000		2,174,000
Deferred revenues		(4,805,000)				(3,671,000)				(4,805,000)		(3,671,000)
Stockholders' equity		21,887,000				24,678,000				21,887,000		24,678,000		$ 28,921,000
Cumulative Effect of New Accounting Principle in Period of Adoption														0
Cost of Revenue		(3,858,000)	$ (3,337,000)	$ (3,495,000)	$ (3,326,000)	(3,375,000)	$ (3,707,000)	$ (3,415,000)	$ (3,805,000)	(14,016,000)	[3]	(14,302,000)	[3]
Additional Paid-in Capital
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' equity		359,339,000				358,123,000				359,339,000		358,123,000		356,746,000
Cumulative Effect of New Accounting Principle in Period of Adoption														$ (675,000)
Accounting Standards Update 2016-09 | New Accounting Pronouncement, Early Adoption, Effect | Additional Paid-in Capital
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption						$ 675,000						$ 675,000
Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue										274,000
Accounts receivable, net		400,000								400,000
Deferred revenues		3,000,000								3,000,000
Cost of Revenue										728,000
Pro Forma [Member] | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue	[1]									31,941,000
Net loss										$ (4,419,000)
Basic and diluted net loss per share										$ (0.99)
Accounts receivable, net	[2]	(2,326,000)								$ (2,326,000)
Deferred cost of goods sold		1,039,000								1,039,000
Deferred revenues		(1,842,000)								(1,842,000)
Stockholders' equity		23,727,000								23,727,000
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue	[1]									274,000
Net loss										$ 204,000
Basic and diluted net loss per share										$ 0.05
Accounts receivable, net	[2]	395,000								$ 395,000
Deferred cost of goods sold		(728,000)								(728,000)
Deferred revenues		2,963,000								2,963,000
Stockholders' equity		$ 1,840,000								$ 1,840,000

[1] Includes related party amounts of $0 and $1,313 in 2017 and 2016, respectively. See Note 13 for additional information on related party transactions.

[2] {F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjcwMjE5NjdjZTI5OTQyODBiNmZlMDMwMWNlNDY3OWQzfFRleHRTZWxlY3Rpb246RkQ1QUNDNTgxNjI0OUE2MzI5RjZERDk4NDlDMEUyNUYM}

[3] See Note 7 for summary of amounts included representing stock-based compensation expense.