Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash flows from operating activities
Net loss	$ (69,421)	$ (78,025)
Adjustments to reconcile net loss to cash used in operating activities
Depreciation	751	435
Amortization of right-of-use assets	809	553
Stock-based compensation expense	8,438	8,070
Non cash interest expense	292
Accretion of discount on marketable securities	(52)	(836)
Loss on disposal of fixed assets	262
Amortization of debt discount and debt issuance costs	4,577	4,184
Premium paid on securities purchased	(17)	(26)
Changes in operating assets and liabilities:
Accounts receivable	15,591	(9,468)
Inventory	(2,502)	(4,512)
Prepaid expenses and other current assets	328	1,287
Accounts payable	(7,540)	(271)
Accrued expenses and other current liabilities	(4,375)	787
Deferred revenue	5,000
Lease liabilities	(748)	(541)
Net cash used in operating activities	(48,607)	(78,363)
Cash flows from investing activities
Purchases of property and equipment	(5,538)	(1,068)
Purchases of marketable securities	(12,490)	(96,198)
Sale and redemption of marketable securities	49,398	138,061
Net cash provided by investing activities	31,370	40,795
Cash flows from financing activities
Proceeds from borrowings under term loan	15,000
Proceeds from revolving line of credit	20,000
Repayments of revolving line of credit	(15,000)
Proceeds from the offering of common stock	97,289
Payments of public offering costs	(107)
Payments on notes payable		(5,000)
Proceeds from the exercise of stock options	10
Proceeds from employee stock purchase plan	891	1,040
Net cash provided by (used in) financing activities	118,083	(3,960)
Net increase (decrease) in cash and cash equivalents	100,846	(41,528)
Cash and cash equivalents at beginning of period	82,253	87,229
Cash and cash equivalents at end of period	183,099	45,701
Non-cash investing and financing activities
Right-of-use asset obtained in exchange for operating lease obligation		7,046
Purchases of property and equipment in accounts payable and accrued expenses	2,126
Public offering costs included in accounts payable or accrued	418
Supplemental disclosures of cash flow information
Cash paid for interest	$ 5,048	$ 3,699