Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities:
Net loss	$ (121,479)	$ (75,811)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization of property, plant and equipment	13,399	8,808
Loss on disposal of property, plant and equipment	211	96
Deferred tax benefit	(984)
Stock-based compensation	36,309	28,056
Loss on settlement of convertible notes	10,558
Non-cash lease expense	1,762
Amortization of liabilities	18,483	10,655
Amortization of premium on short-term investments	(2,580)	(1,392)
Amortization of intangible assets	1,615	1,228
Changes in assets and liabilities:
Accrued interest	(1,302)	4,154
Accounts receivable, net	(18,574)	(9,849)
Inventory, net	(8,633)	(9,382)
Prepaid expenses and other current assets	(4,282)	(6,410)
Accounts payable	(8,245)	(5,143)
Accrued liabilities	33,487	(9,798)
Other short-term liabilities	84	69
Other long-term liabilities	16,980	683
Other long-term assets	(24,055)
Net cash used in operating activities	(57,246)	(64,036)
Cash flows from investing activities:
Purchases of marketable securities	(511,587)	(894,856)
Maturities of marketable securities	447,674	245,842
Purchases of property, plant and equipment	(79,448)	(44,364)
Internally developed software	(380)	(131)
Net cash used in investing activities	(143,741)	(693,509)
Cash flows from financing activities:
Proceeds from issuance of convertible notes, net	729,479	896,425
Proceeds from exercise of common stock options	4,998	5,645
Proceeds in connection with the Company's employee stock purchase plan	4,137	2,661
Payments on settlement of convertible notes	(493,356)
Payments of deferred financing costs		(24)
Proceeds from construction loan	319	1,097
Payments on mortgage payable		(90)
Net cash provided by financing activities	245,577	905,714
Effects of exchange rate changes on cash and cash equivalents	38	2
Net increase in cash and cash equivalents	44,628	148,171
Cash and cash equivalents, beginning of period	160,430	77,491
Cash and cash equivalents, end of period	205,058	225,662
Supplemental disclosure of non-cash investing and financing activities:
Property, plant and equipment acquired but not paid	24,402	25,021
Unrealized gain (loss) on available-for-sale investments, before tax	4,128	(1,130)
Issuance of 86,532 and 86,882 shares of common stock to fund the Company's 401(k) matching contribution for 2018 and 2017, respectively	7,409	4,303
Issuance of 2,158,991 shares of common stock upon settlement of convertible notes	182,435
Retirement of equity component of convertible notes settled	(300,768)
Interest paid	$ 5,388	$ 97