Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash flows from operating activities:
Net loss	$ (26,505)	$ (83,496)
Adjustments to reconcile net loss to net cash used in operating activities:
Share-based compensation	4,493	5,762
Depreciation and amortization expense	1,229	5,479
Change in fair value of warrant and private placement option liabilities	(14,256)	4,850
(Gain) loss on dispositions, net	(3,761)	4
Amortization of discount on investment securities, net	0	(29)
Amortization of right-of-use assets	297	996
Accretion of lease liability	371	590
Amortization of deferred issuance costs	550	662
Expense of issuance costs on warrants and private placement option	0	3,047
Changes in operating assets and liabilities:
Accounts receivable, interest and other receivables	178	581
Prepaid expenses and other assets	103	(1,524)
Accounts payable	(1,345)	(2,474)
Accrued liabilities and other	(4,629)	2,727
Deferred revenue	0	(2,010)
Net cash used in operating activities	(43,275)	(64,835)
Cash flows from investing activities:
Proceeds from sale of investment securities	0	45,229
Proceeds from sale of property and equipment, net	14,909	0
Purchases of property and equipment	(807)	(554)
Net cash provided by investing activities	14,102	44,675
Cash flows from financing activities:
Payment on debt	(10,000)	0
Proceeds from issuance of common stock in a public offering, net	0	8,977
Proceeds from issuance of redeemable convertible preferred stock in a public offering, net	0	22,944
Proceeds from issuance of warrants in a public offering, net	0	30,995
Proceeds upon entering into private placement agreement	0	11,254
Proceeds from issuance of stock from employee stock purchase plan	65	71
Proceeds from exercise of stock options	0	76
Payment on financing lease obligations	(56)	(30)
Net cash (used in) provided by financing activities	(9,991)	74,287
Effect of exchange rate changes on cash	(26)	(41)
Net change in cash, cash equivalents, and restricted cash	(39,190)	54,086
Cash, cash equivalents and restricted cash at beginning of period	93,816	48,668
Cash, cash equivalents and restricted cash at end of period	54,626	102,754
Supplemental cash flow information:
Cash paid during the period for interest	1,973	2,611
Non-cash investing and financing activities:
Purchases of property and equipment in accounts payables and accrued liabilities	859	0
Leasehold improvements paid by landlord	113	0
Conversion of redeemable preferred stock into common stock	160	1,336
Reclassification of property and equipment, net to assets held for sale	199	0
Accrued issuance costs for public offering	0	210
Financing leases incurred for equipment	$ 0	$ 167