Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net loss	$ (121,175)	$ (92,633)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization of property and equipment	14,349	10,507
Loss on disposal of property and equipment	853	301
Deferred tax benefit		(231)
Stock-based compensation	44,554	23,002
Amortization of debt discount	18,559
Amortization of debt issuance costs	1,597
Amortization of other liabilities	(1,809)	(1,199)
Amortization of deferred financing costs	86	40
Amortization of premium on short-term investments	(2,581)	56
Amortization of intangible assets	1,847	645
Changes in assets and liabilities, net effects of acquisition:
Accrued interest	1,901
Accounts receivable, net	(15,497)	(15,663)
Inventory, net	(12,590)	(11,231)
Prepaid expenses and other current assets	(13,777)	(1,391)
Accounts payable	16,603	8,022
Accrued liabilities	(1,600)	9,306
Other short-term liabilities	87	(29)
Lease incentive obligation	504	(462)
Net cash used in operating activities	(68,089)	(70,960)
Cash flows from investing activities:
Purchases of marketable securities	(1,081,662)	(345,039)
Maturities of marketable securities	407,287	195,485
Purchases of property and equipment	(97,987)	(24,442)
Business acquisition, net of cash acquired		(2,996)
Purchases of intangible assets		(8,442)
Internally developed software	(135)	(25)
Net cash used in investing activities	(772,497)	(185,459)
Cash flows from financing activities:
Proceeds from issuance of convertible notes, net	896,431
Proceeds from financing obligation	6,750
Proceeds from exercise of common stock options	6,376	3,350
Proceeds from sale of common stock, net of issuance costs		253,389
Proceeds in connection with the Company's employee stock purchase plan	2,663	1,629
Payments of deferred financing costs	(25)
Proceeds from construction loan	17,271
Payments on mortgage payable	(4,678)	(130)
Net cash provided by financing activities	924,788	258,238
Effects of exchange rate changes on cash and cash equivalents	12	97
Net increase in cash and cash equivalents	84,214	1,916
Cash and cash equivalents, beginning of period	77,491	48,921
Cash and cash equivalents, end of period	161,705	50,837
Supplemental disclosure of non-cash investing and financing activities:
Property and equipment acquired but not paid	25,714	3,930
Unrealized gain (loss) on available-for-sale investments	(668)	7
Issuance of 86,882 and 158,717 shares of common stock to fund the Company’s 401(k) matching contribution for 2017 and 2016, respectively	4,303	3,008
Interest paid	$ 4,638	$ 151