Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash flows from operating activities:
Net loss	$ (115,454)	$ (72,829)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	30,985	19,354
Amortization of other intangible assets acquired	151	301
Depreciation and amortization	3,781	1,543
Net amortization/accretion on investment securities	20	(2,285)
Non-cash rent expense	1,060	1,548
Benefit from income taxes	0	(209)
Share of losses from equity method investments	215	0
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	4,116	(521)
Other long-term assets	2,458	(1,993)
Accounts payable	(503)	1,332
Accrued and other current liabilities	6,829	(107)
Other long-term liabilities	(1,188)	(1,282)
Net cash used in operating activities	(67,530)	(55,148)
Cash flows from investing activities:
Purchases of property and equipment	(28,307)	(18,279)
Proceeds from sales of investments	4,877	0
Proceeds from maturities of investments	221,633	197,415
Purchase of investments	(642,181)	(101,756)
Net cash (used in) provided by investing activities	(443,978)	77,380
Cash flows from financing activities:
Proceeds from issuance of common stock upon exercise of stock options	4,780	236
Proceeds from issuance of common stock under the employee stock purchase plan	1,438	684
Net cash provided by financing activities	616,761	920
Net change in cash, cash equivalents and restricted cash	105,253	23,152
Cash, cash equivalents and restricted cash — beginning of period	179,425	93,731
Cash, cash equivalents and restricted cash — end of period	284,678	116,883
Non-cash investing activities:
Property and equipment purchases in accounts payable and accrued liabilities	8,298	13,667
Supplemental disclosure:
Cash paid for amounts included in the measurement of lease liabilities	2,816	1,156
Cash received for amounts related to tenant improvement allowances	1,617	0
ATM offering
Cash flows from financing activities:
Proceeds from issuance of common stock, net of commissions and issuance costs	14,845	0
Public offering
Cash flows from financing activities:
Proceeds from issuance of common stock, net of commissions and issuance costs	$ 595,698	$ 0