Supplemental Cash Flow Information - Cash Payments and Non-Cash Activity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Supplemental cash flow information:
Cash paid for interest	$ 6	$ 4	$ 9
Cash paid for income taxes	5,498	5,813	2,488
Supplemental noncash investing and financing activities:
Transfer of service and sales demonstration inventory to fixed assets	$ 3,044	$ 964	$ 2,844