Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities:
Net loss	$ (14,770)	$ (10,533)
Adjustments to reconcile net loss to net cash used in operating activities:
Provision for uncollectible accounts	170
Write-downs of excess and obsolete inventories	106	101
Depreciation and amortization	386	445
Debt related amortization included in interest expense	301	268
Stock-based compensation	1,126	551
Amortization of operating lease right-of-use assets	104
Changes in operating assets and liabilities:
Trade accounts receivable	1,909	1,795
Inventories	(1,566)	399
Prepaid expenses and other current assets	469	94
Accounts payable and other current liabilities	(1,847)	(1,350)
Accrued compensation	(3,955)	(1,594)
Other long-term liabilities	(130)	13
Net cash used in operating activities	(17,697)	(9,811)
Cash flows from investing activities:
Acquisition of property, plant and equipment	(526)	(90)
Net cash used in investing activities	(526)	(90)
Cash flows from financing activities:
Borrowings under credit facility, net		11,711
Proceeds from the sale of common stock		24,046
Payments of financing costs related to issuance of common stock		(246)
Proceeds from the exercise of stock options	301	76
Payment of debt issuance costs and other financing activities	(8)
Net cash provided by financing activities	293	35,587
Net (decrease) increase in cash and cash equivalents	(17,930)	25,686
Cash and cash equivalents, beginning of period	99,240	28,165
Cash and cash equivalents, end of period	81,310	53,851
Supplemental Disclosure of Cash Flow Information:
Income taxes paid
Interest paid	1,076	622
Acquisition of property, plant and equipment accrued not paid	$ 48	$ 96