Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities:
Net loss	$ (14,344)	$ (26,058)
Adjustments to reconcile net loss to net cash used by operating activities:
Depreciation and amortization expense	2,136	1,953
Stock-based compensation expense	2,106	1,784
Unrealized foreign exchange (gain)/loss, net	229	1,085
Non-cash lease expense	584
Provision for bad debts on trade receivables	(19)	(22)
Disposal of long term-assets	0	(2)
Loss on extinguishment of debt	1,085	0
Non-cash interest expense	217	55
Amortization/accretion on investments	(4)	51
Deferred tax	0	(17)
Changes in operating assets and liabilities:
Accounts receivable	2,013	1,207
Royalty receivable	(23)	0
Inventories	(1,104)	124
Prepaid expenses and other assets	(324)	207
Accounts payable, accrued expenses and other liabilities	(564)	2,054
Net cash used in operating activities	(8,012)	(17,579)
Cash flows from investing activities:
Acquisition of property and equipment	(1,298)	(2,342)
Purchase of investments	0	(14,196)
Maturity of investments	7,250	23,595
Net cash provided in investing activities	5,952	7,057
Cash flows from financing activities:
Proceeds from exercise of common stock options	121	112
Debt issuance costs	685	0
Loss on extinguishment of debt	(1,085)	0
Proceeds from issuance of debt	20,000	0
Payments on long-term debt	(15,000)	0
Net proceeds from issuance of common stock	3,000	21,324
Net cash provided by financing activities	6,351	21,436
Foreign exchange effect on cash and cash equivalents	(12)	(140)
Increase in cash and cash equivalents	4,279	10,774
Cash and cash equivalents, beginning of period	16,380	18,348
Cash and cash equivalents, end of period	20,659	29,122
Supplemental information:
Cash paid for interest	1,425	$ 1,234
Noncash Investing and Financing Items [Abstract]
Operating leases right-of-use assets obtained in exchange for lease obligations	$ 6,988