Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities:
Net loss	$ (39,424)	$ (34,946)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization of fixed assets	4,281	3,247
Loss on disposal of property and equipment	98	20
Stock-based compensation	12,463	6,129
Amortization of debt discount	4,651
Amortization of debt issuance costs	402
Amortization of other liabilities	(533)	(377)
Amortization of deferred financing costs	23	14
Amortization of premium on short-term investments	(515)	37
Amortization of intangible assets	612	50
Changes in assets and liabilities, net effects of acquisition:
Accrued interest	1,407
Accounts receivable, net	(8,156)	(7,688)
Inventory, net	(6,353)	(1,026)
Prepaid expenses and other current assets	(2,812)	(329)
Accounts payable	(3,861)	181
Accrued liabilities	(623)	1,204
Other short-term liabilities	(29)	(154)
Lease incentive obligation	(153)
Net cash used in operating activities	(38,522)	(33,638)
Cash flows from investing activities:
Purchases of marketable securities	(628,502)	(30,563)
Maturities of marketable securities	81,161	57,236
Purchases of property and equipment	(15,328)	(2,745)
Internally developed software	(62)
Net cash (used in) provided by investing activities	(562,731)	23,928
Cash flows from financing activities:
Proceeds from issuance of convertible notes, net	671,091
Proceeds from exercise of common stock options	1,391	47
Payments on mortgage payable	(45)	(44)
Net cash provided by financing activities	672,437	3
Effects of exchange rate changes on cash and cash equivalents	20	(8)
Net increase (decrease) in cash and cash equivalents	71,204	(9,715)
Cash and cash equivalents, beginning of period	77,491	48,921
Cash and cash equivalents, end of period	148,695	39,206
Supplemental disclosure of non-cash investing and financing activities:
Property and equipment acquired but not paid	12,513	775
Unrealized gain (loss) on available-for-sale investments	(1,606)	(5)
Issuance of 86,828 and 158,717 shares of common stock to fund the Company’s 401(k) matching contribution for 2017 and 2016, respectively	4,300	3,008
Interest paid	$ 48	$ 50