CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Cash flows from operating activities:
Net loss	$ (72,389)	$ (41,519)
Adjustments to reconcile net loss to cash used in operating activities:
Depreciation	614	243
Non-cash operating lease cost	1,307	283
Amortization of debt discount and other non-cash interest	709	75
Stock-based compensation	7,666	6,417
Loss on disposal of fixed asset		9
Change in operating assets and liabilities:
Accounts receivable	(7,171)
Prepaid expenses and other current assets	(167)	(3,350)
Inventory	(4,379)	(910)
Accounts payable	(3,284)	(220)
Accrued expenses	3,454	1,143
Lease liabilities and other long-term liabilities	(868)	(303)
Net cash used in operating activities	(74,508)	(38,132)
Cash flows from investing activities:
Purchases of property and equipment	(1,147)	(668)
Net cash used in investing activities	(1,147)	(668)
Cash flows from financing activities:
Proceeds from venture debt, net of debt issuance costs of $50		2,728
Payment of principal and prepayment penalty on venture debt		(1,667)
Payment of principal on finance lease	(30)
Payment of deferred offering costs		(163)
Proceeds from common stock offerings, net of offering cost	2,130
Proceeds from exercise of stock options and issuance of common stock under employee stock purchase plan	587	291
Net cash provided by financing activities	2,687	1,189
Net decrease in cash and restricted cash:	(72,968)	(37,611)
Cash and restricted cash at beginning of period	183,104	114,699
Cash and restricted cash at end of period	110,136	77,088
Reconciliation of cash and restricted cash:
Cash and restricted cash at end of period	183,104	114,699
Non-cash investing and financing activities:
Right-of-use asset obtained in exchange for finance lease obligation	136
Purchases of property and equipment in accounts payable		110
Supplemental disclosure:
Cash paid for interest	5,626	$ 1,138
Right-of-use assets obtained in exchange of operating lease obligations	$ 1,852