Supplemental Disclosure of Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Supplemental disclosure of cash flow activities:
Cash paid for income taxes	$ 416	$ 941	$ 505
Cash paid for interest expense	101	12	10
Supplemental disclosure of non-cash investing and financing activities:
Common stock issued for settlement of restricted stock unit awards	3,206	1,020	1,308
Purchase of property and equipment in accounts payable and accrued expenses	13	158	1,093
Contingent consideration on acquisition	$ 0	$ 0	$ 926