Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash flow from operating activities:
Net loss	$ (79,124)	$ (72,965)
Adjustments to reconcile net loss to net cash used in operating activities
Stock-based compensation	14,697	9,581
Depreciation and amortization	740	552
Deferred income taxes	(17,425)	0
Noncash lease expense	619	0
Net accretion and amortization of investments in marketable securities	(380)	(3,299)
Change in fair value of warrant liabilities	(162)	158
Acquired in-process research and development expense	3,000	0
Change in fair value of contingent consideration	4,300	2,300
Changes in operating assets and liabilities:
Inventory, net	(475)	0
Prepaid expenses and other current assets	251	6,071
Other assets	(1,171)	(5,963)
Accounts payable, accrued and other liabilities	(5,737)	(5,193)
Operating lease liability	(634)	12,588
Deferred revenue	(2,281)	14,431
Net cash used in operating activities	(83,782)	(41,739)
Cash flow from investing activities:
Cash paid for in-process research and development asset	(3,000)	0
Purchases of marketable securities	(180,832)	(251,782)
Proceeds from maturities of marketable securities	114,205	289,357
Proceeds from sales of marketable securities	2,988	0
Purchases of property and equipment	(415)	(8,922)
Net cash (used in) provided by investing activities	(67,054)	28,653
Cash flow from financing activities:
Payment of contingent consideration	0	(10,000)
Proceeds from issuance of common stock under equity incentive plans	4,498	6,026
Taxes paid related to net share settlement of equity awards	(569)	(606)
Proceeds from issuance of common stock, net of issuance costs	221,708	0
Net cash provided by (used in) financing activities	225,637	(4,580)
Net increase (decrease) in cash and cash equivalents	74,801	(17,666)
Cash and cash equivalents, beginning of the period	62,070	68,454
Cash and cash equivalents, end of the period	$ 136,871	$ 50,788