Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities
Net loss	$ (232,569)	$ (145,105)	$ (99,059)
Adjustments to reconcile net loss to net cash used in operating activities
Depreciation	2,442	1,410	970
Amortization of debt issuance costs and fees	1,577	306	303
Amortization and accretion of premium or discount on investments, net	69	9	525
Acquisition of assets expensed to research and development	0	24,802	0
Stock-based compensation	38,728	26,078	16,794
Induced conversion of convertible notes	24,059	0	0
Unrealized foreign exchange (gain) loss	(270)	601	0
Changes in operating assets and liabilities
Accounts receivable, net	(2,715)	0	0
Inventory	(9,689)	0	0
Prepaid, current and other assets	(791)	(2,239)	(1,852)
Accounts payable, accrued expenses and other current liabilities	26,583	925	2,479
Net cash used in operating activities	(152,576)	(93,213)	(79,840)
Cash flows from investing activities
Acquisition of assets from Envisia	0	(10,500)	0
Purchase of available-for-sale investments	(56,195)	(104,490)	(35,169)
Proceeds from sales and maturities of investments	108,297	88,153	58,346
Purchase of property, plant and equipment	(31,313)	(15,970)	(5,077)
Net cash provided by (used in) investing activities	20,789	(42,807)	18,100
Cash flows from financing activities
Proceeds from sale of common stock, net	135,972	134,215	167,383
Proceeds related to issuance of stock for stock-based compensation arrangements, net	3,630	1,429	1,242
Payments of debt issuance costs	(1,883)	0	0
Other financing	(683)	0	0
Net cash provided by financing activities	137,036	135,644	168,625
Net change in cash and cash equivalents	5,249	(376)	106,885
Cash and cash equivalents, at beginning of period	197,569	197,945	91,060
Cash and cash equivalents, at end of period	202,818	197,569	197,945
Supplemental disclosures
Cash paid for interest	1,774	2,188	2,192
Cash paid for income taxes	0	0	1,790
Non-cash investing and financing activities:
Conversion of convertible notes to common stock (Note 9)	148,078	0	0
Purchases of property, plant and equipment	3,526	4,176	482
Acquisition of capital lease obligation	0	689	0
Deferred costs from the sale of common stock	0	403	70
Build-to-suit lease transaction (Note 7)
Envisia Therapeutics Inc.
Non-cash investing and financing activities:
Equity issued for Envisia Asset Acquisition	$ 0	$ 14,302	$ 0