The Company, Adoption of New Accounting Standards (Details) - USD ($) $ in Thousands	3 Months Ended						6 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2018	Jun. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Operations and Other Comprehensive Loss [Abstract]
Revenues, net	$ 7,729	$ 7,388	$ 6,738	$ 7,456	$ 8,445	$ 7,269	$ 14,126	$ 15,714	$ 21,856	$ 23,169	$ 29,855	$ 31,763
Balance Sheet [Abstract]
Deferred revenue	1,877	1,802	1,725	1,952	2,210	2,132	1,802	2,210	1,877	1,952	2,099	1,871	$ 2,230
Other liabilities	$ 269	$ 288	$ 649	$ 412	$ 724	$ 752	$ 288	$ 724	$ 269	$ 412	388	444
ASU 2014-09 [Member]
Net Assets, Adjusted Balance [Abstract]
Cumulative accounting adjustment from adoption of new standard, net of tax												(234)
ASU 2014-09 [Member] | Accumulated Deficit [Member]
Net Assets, Adjusted Balance [Abstract]
Cumulative accounting adjustment from adoption of new standard, net of tax												(234)
ASU 2014-09 [Member] | Additional Paid-In Capital [Member]
Net Assets, Adjusted Balance [Abstract]
Cumulative accounting adjustment from adoption of new standard, net of tax												0
ASU 2017-11 [Member]
Net Assets, Adjusted Balance [Abstract]
Cumulative accounting adjustment from adoption of new standard, net of tax												67
ASU 2017-11 [Member] | Accumulated Deficit [Member]
Net Assets, Adjusted Balance [Abstract]
Cumulative accounting adjustment from adoption of new standard, net of tax												(2,547)
ASU 2017-11 [Member] | Additional Paid-In Capital [Member]
Net Assets, Adjusted Balance [Abstract]
Cumulative accounting adjustment from adoption of new standard, net of tax												$ 2,614
ASU 2016-02 [Member]
Balance Sheet [Abstract]
Right-of-use assets											848
Lease liabilities											848
Balances Without Adoption of ASC 606 [Member] | ASU 2014-09 [Member]
Statement of Operations and Other Comprehensive Loss [Abstract]
Revenues, net											30,051
Balance Sheet [Abstract]
Deferred revenue											1,937
Other liabilities											120
Effect of Adoption Higher / (Lower) [Member] | ASU 2014-09 [Member]
Statement of Operations and Other Comprehensive Loss [Abstract]
Revenues, net											(196)
Balance Sheet [Abstract]
Deferred revenue											162
Other liabilities											$ 268