Summary of Significant Accounting Policies - Reconciliation of Basic and Diluted Income (Loss) per Share (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Numerator:
Loss from continuing operations									$ (9,111)	$ (11,267)	$ (16,875)
Loss from discontinued operations									0	0	(12)
Net loss	$ (3,000)	$ (1,920)	$ (1,801)	$ (2,390)	$ (1,858)	$ (1,773)	$ (3,114)	$ (4,522)	$ (9,111)	$ (11,267)	$ (16,887)
Denominator:
Basic weighted average common shares outstanding (in shares)									11,997	11,806	11,673
Potential common shares from options and warrants (in shares)									0	0	0
Diluted weighted average shares (in shares)									11,997	11,806	11,673