Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($)	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
OPERATING ACTIVITIES:
Net loss	$ (58,991,000)	$ (68,161,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	4,967,000	3,814,000
Unrealized translation losses on obligation related to royalty	(251,000)	854,000
Non-cash stock-based compensation	4,288,000	2,098,000
Non-cash interest expense	(10,000)	573,000
Loss on debt extinguishment	0	5,075,000
Amortization of premium or discounts on marketable securities	41,000	329,000
Changes in operating assets and liabilities:
Accounts receivable	(1,853,000)	(3,849,000)
Inventory	212,000	(2,620,000)
Prepaid expenses and other current assets	(2,483,000)	(247,000)
Other assets	97,000	(22,000)
Accounts payable	3,348,000	3,289,000
Accrued compensation	2,519,000	1,240,000
Accrued expenses and other current liabilities	541,000	1,807,000
Deferred rent	1,086,000	(456,000)
Deferred revenue	842,000	2,030,000
Net cash used in operating activities	(45,647,000)	(54,246,000)
INVESTING ACTIVITIES:
Purchase of marketable securities	(48,693,000)	(119,714,000)
Maturity of marketable securities	110,625,000	49,944,000
Purchase of property and equipment	(17,272,000)	(3,719,000)
Payment in connection with a license agreement	0	(1,102,000)
Net cash provided by (used in) investing activities	44,660,000	(74,591,000)
FINANCING ACTIVITIES:
Payment related to settlement of debt and buyout of royalty obligations	0	(25,844,000)
Payments made on capital lease obligations	(420,000)	(199,000)
Proceeds from issuance of convertible preferred stock, net of issuance costs	0	319,536,000
Proceeds from issuance of common stock upon exercise of stock options	2,572,000	669,000
Proceeds from issuance of common stock upon the exercise of warrants	38,000	7,000
Repurchase of convertible preferred stock	0	(5,335,000)
Repurchase of common stock	(172,000)	(7,222,000)
Payment of offering costs related to initial public offering	(221,000)	0
Net proceeds from issuance of equity interests in redeemable noncontrolling interest	41,000,000	0
Net cash provided by financing activities	42,797,000	281,612,000
Net effect of foreign exchange rate changes on cash, cash equivalents, and restricted cash	(27,000)	0
Net increase in cash, cash equivalents and restricted cash	41,783,000	152,775,000
Cash, cash equivalents and restricted cash - Beginning of period	72,596,000	33,591,000
Cash, cash equivalents and restricted cash - End of period	114,379,000	186,366,000
Supplemental Disclosures of Cash Flow Information:
Cash paid for interest	67,000	1,318,000
Cash paid for income taxes	0	26,000
Supplemental Disclosures of Noncash Investing and Financing Activities:
Capitalized license fees financed through future royalty payment	0	6,302,000
Increase in purchases of property and equipment included in accounts payable and accrued expenses	0	346,000
Property and equipment acquired under capital leases	1,234,000	2,243,000
Purchases of capitalized license fee included in accrued expenses	0	1,200,000
Deferred offering costs included in accounts payable and accrued expenses	4,036,000	0
Convertible Preferred Stock
Supplemental Disclosures of Noncash Investing and Financing Activities:
Stock issued	0	1,060,000
Common Stock
Supplemental Disclosures of Noncash Investing and Financing Activities:
Stock issued	$ 0	$ 36,000