Income Taxes - Schedule of Changes in Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance of unrecognized tax benefits	$ 250	$ 167	$ 117
Additions for current year tax positions	65	75	50
Ending balance (excluding interest and penalties)	315	242	167
Interest and penalties	11	8
Total	$ 326	$ 250	$ 167