Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
OPERATING ACTIVITIES:
Net loss	$ (45,741)	$ (58,991)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	7,963	4,967
Unrealized translation gains on obligation related to royalty	(330)	(251)
Non-cash stock-based compensation	11,882	4,288
Non-cash interest expense	0	(10)
Amortization of discounts on marketable securities	(1,953)	41
Benefit from income taxes	(1,235)	0
Changes in operating assets and liabilities:
Accounts receivable	908	(1,853)
Inventory	(5,624)	212
Prepaid expenses and other current assets	(453)	(2,483)
Other assets	(1,043)	97
Accounts payable	426	3,348
Accrued compensation	11,618	2,519
Accrued expenses and other liabilities	6,368	541
Deferred rent	3,465	1,086
Deferred revenue	(3,043)	842
Net cash used in operating activities	(16,792)	(45,647)
INVESTING ACTIVITIES:
Purchases of marketable securities	(542,468)	(48,693)
Maturity of marketable securities	223,064	110,625
Business acquisition, net of cash acquired	(7,328)	0
Purchases of property and equipment	(11,628)	(17,272)
Purchases of intangible assets and capitalized license obligations	(2,568)	0
Net cash (used in) provided by investing activities	(340,928)	44,660
FINANCING ACTIVITIES:
Payments made on royalty obligations	(228)	0
Payments made on capital lease obligations	(79)	(420)
Proceeds from issuance of common stock upon exercise of stock options	9,795	2,572
Proceeds from issuance of common stock upon the exercise of warrants	0	38
Repurchase of common stock	0	(172)
Proceeds from issuances of common stock under employee stock purchase plan	5,118	0
Proceeds from follow-on offering, net of underwriting discounts and commissions	350,432	0
Payment of offering costs related to initial public offering and follow-on offering	(811)	(221)
Net proceeds from issuance of equity interests in redeemable noncontrolling interest	0	41,000
Net cash provided by financing activities	364,227	42,797
Net effect of foreign exchange rate changes on cash, cash equivalents, and restricted cash	137	(27)
Net increase in cash, cash equivalents and restricted cash	6,644	41,783
Cash, cash equivalents and restricted cash - Beginning of period	140,544	72,596
Cash, cash equivalents and restricted cash - End of period	147,188	114,379
Supplemental Disclosures of Cash Flow Information:
Cash paid for interest	860	67
Cash paid for income taxes	298	0
Supplemental Disclosures of Noncash Investing and Financing Activities:
Purchases of property and equipment included in accounts payable and accrued expenses	6,418	1,859
Deferred offering costs included in accounts payable and accrued expenses	0	4,036
Initial fair value of contingent consideration at acquisition date	$ 1,065	$ 0