CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities:
Net loss	$ (227,413)	$ (209,383)	$ (419,503)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	35,463	29,176	21,247
Depreciation and amortization	9,455	5,465	1,268
Deferred income taxes	0	(17,425)	0
Noncash lease expense	1,143	1,137	1,221
Amortization of debt discount and issuance costs	8,812	2,143	0
Net accretion and amortization of investments in marketable securities	(20)	(570)	(4,887)
Acquired in-process research and development (IPR&D)	0	10,700	251,437
Change in fair value of contingent consideration	1,885	8,600	5,600
Other	(2)	(205)	(471)
Changes in operating assets and liabilities:
Accounts receivable	(6,315)	(3,824)	0
Inventory	(3,474)	(1,026)	0
Prepaid expenses and other current assets	(25,007)	(575)	7,573
Other assets	4,480	(1,613)	(5,723)
Accounts payable, accrued and other current liabilities	21,330	13,711	5,647
Contingent consideration liability	(1,500)	0	0
Operating lease liability	(1,691)	(1,287)	11,720
Deferred revenue	(2,451)	(2,555)	13,352
Net cash used in operating activities	(185,305)	(167,531)	(111,519)
Cash flows from investing activities:
Cash paid for IPR&D assets	0	(10,700)	(179,624)
Purchase of Tevard note receivable	0	(5,000)	0
Purchases of marketable securities	(416,155)	(509,335)	(329,641)
Proceeds from maturities of marketable securities	540,133	347,627	415,020
Proceeds from sale of marketable securities	13,500	12,987	176,858
Purchases of property and equipment	(83)	(679)	(9,492)
Net cash provided by (used in) investing activities	137,395	(165,100)	73,121
Cash flows from financing activities:
Payments for contingent consideration liability	(18,000)	(15,000)	(20,000)
Proceeds from issuance of common stock under equity incentive plans	1,962	5,515	10,182
Payments of tax withholding obligation on vesting restricted stock units	(1,788)	(2,157)	(744)
Net proceeds from issuance of convertible debt	0	223,100	0
Payment of debt issuance costs	0	(557)	0
Proceeds from issuance of common stock, net	0	226,576	42,576
Net cash provided by financing activities	(17,826)	437,477	32,014
Net increase (decrease) in cash and cash equivalents	(65,736)	104,846	(6,384)
Cash and cash equivalents at beginning of period	166,916	62,070	68,454
Cash and cash equivalents at end of period	101,180	166,916	62,070
Supplemental Cash Flow Information [Abstract]
Cash paid for interest	6,378	0	0
Noncash investing and financing activities:
Common stock issued as consideration for asset acquisition	0	0	68,124
Net liabilities assumed in connection with asset acquisition	$ 0	$ 0	$ 3,688