CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities:
Net loss	$ (181,915)	$ (141,214)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation, amortization and accretion, net	12,210	3,178
Stock-based compensation	32,032	19,584
Charge for 401(k) company stock match	1,089	942
Fair value adjustments on marketable equity securities	(21)
Changes in operating assets and liabilities:
Accounts receivable, net	(15,041)	(16,766)
Proceeds from landlord lease incentive for tenant improvements	12,386
Inventory	(7,134)
Prepaid expenses and other assets	(9,418)	(27,540)
Accounts payable	(17,133)	(9,042)
Accrued expenses and other	(14,731)	(11,767)
Deferred revenue	(834)	26,961
Net cash used in operating activities	(188,510)	(155,664)
Cash flows from investing activities:
Purchases of property, plant and equipment	(44,049)	(21,257)
Purchases of marketable debt securities	(256,996)	(358,433)
Sales and maturities of marketable securities	403,697	244,876
Net cash provided by (used in) investing activities	102,652	(134,814)
Cash flows from financing activities:
Proceeds from exercise of stock options and other types of equity	9,083	42,094
Offering proceeds, net of costs	381,900
Payments for repurchase of common stock for employee tax withholding	(52)	(572)
Net cash provided by financing activities	390,931	41,522
Net increase (decrease) in cash, cash equivalents and restricted cash	305,073	(248,956)
Cash, cash equivalents and restricted cash, beginning of period	422,631	646,832
Cash, cash equivalents and restricted cash, end of period	727,704	397,876
Supplemental disclosure of noncash investing activities:
Capital expenditures included in accounts payable and accrued expenses	$ 13,033	$ 10,437