Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
OPERATING ACTIVITIES:
Net loss	$ (32,651)	$ (35,483)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	5,011	2,964
Unrealized translation gains on obligation related to royalty	(51)	(205)
Non-cash stock-based compensation	6,397	2,457
Non-cash interest expense	0	(7)
Amortization of discounts on marketable securities	(1,276)	150
Changes in operating assets and liabilities:
Accounts receivable	234	2,224
Inventory	(5,040)	559
Prepaid expenses and other current assets	1,122	(1,496)
Deferred tax assets	(1,235)	0
Other assets	(1,129)	255
Accounts payable	3,413	823
Accrued compensation	701	51
Accrued expenses and other liabilities	2,939	2,482
Deferred rent	3,068	866
Deferred revenue	358	760
Net cash used in operating activities	(18,139)	(23,600)
INVESTING ACTIVITIES:
Purchase of marketable securities	(418,841)	(44,070)
Maturity of marketable securities	129,160	75,625
Business acquisitions, net of cash acquired	(9,765)	0
Purchase of property and equipment	(5,752)	(11,360)
Net cash (used in) provided by investing activities	(305,198)	20,195
FINANCING ACTIVITIES:
Payments made on royalty obligations	(151)	0
Payments made on capital lease obligations	(62)	(399)
Proceeds from issuance of common stock upon exercise of stock options	5,530	1,734
Proceeds from issuance of common stock upon the exercise of warrants	0	6
Repurchase of common stock	0	(172)
Proceeds from issuances of common stock under employee stock purchase plan	1,933	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	(326)	(168)
Net proceeds from issuance of equity interests in redeemable noncontrolling interest	0	41,000
Net cash provided by financing activities	357,356	42,001
Net effect of foreign exchange rate changes on cash, cash equivalents, and restricted cash	90	0
Net increase in cash, cash equivalents and restricted cash	34,109	38,596
Cash, cash equivalents and restricted cash - Beginning of period	140,544	72,596
Cash, cash equivalents and restricted cash - End of period	174,653	111,192
Supplemental Disclosures of Cash Flow Information:
Cash paid for interest	580	51
Supplemental Disclosures of Noncash Investing and Financing Activities:
Purchases of property and equipment included in accounts payable and accrued expenses	3,874	4,986
Deferred offering costs included in accounts payable and accrued expenses	485	1,794
Initial fair value of contingent consideration at acquisition date	$ 1,135	$ 0