Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018		Mar. 31, 2017
Cash flows from operating activities:
Net loss	$ (12,669)		$ (6,695)
Adjustments to reconcile net loss to net cash used in operating activities:
Provision for doubtful accounts	42
Depreciation and amortization	150		107
Stock-based compensation	753		372
Non-cash interest expense	386		35
Loss from minority interest in limited liability company	249
Changes in assets and liabilities:
Accounts receivable	(828)		(1,929)
Inventory	(1,497)		40
Prepaid expenses and other current assets	(561)		(174)
Other noncurrent assets	(2)		(16)
Accounts payable	(934)		273
Accrued and other liabilities	(366)		(99)
Other noncurrent liabilities	86		37
Net cash used in operating activities	(15,191)		(8,049)
Cash flows from investing activities:
Purchase of property and equipment	(462)		(151)
Net cash used in investing activities	(462)		(151)
Cash flows from financing activities:
Proceeds from sale of common stock, net of issuance costs	33,236		31,503
Proceeds from issuance of common shares from employee stock purchase plan	65
Net cash provided by financing activities	33,301		31,503
Net increase in cash and cash equivalents	17,648		23,303
Cash and cash equivalents - beginning of period	20,730	[1]	8,086
Cash and cash equivalents - end of period	38,378		31,389
Supplemental disclosure:
Cash paid for interest	653		194
Cash paid for income taxes
Supplemental disclosure of cash flow information as of end of period:
Issuance of note payable in settlement of accrued interest	305
Net transfer of equipment between inventory and property and equipment	$ 59		$ 264

[1] The condensed consolidated balance sheet as of December 31, 2017 has been derived from the audited consolidated financial statements as of that date.