Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 297,098	$ 185,383
Investments	185,621	118,732
Prepaid expenses and other assets	4,626	3,639
Total current assets	487,345	307,754
Property and equipment, net	19,206	29,521
Goodwill	30,815	30,815
Restricted cash	1,568	1,525
Deposits	455	455
Operating lease right-of-use assets	914	2,051
Finance lease right-of-use asset	50,521	0
Total assets	590,824	372,121
Current liabilities:
Accounts payable and accrued expenses	25,472	17,352
Convertible notes, net of unamortized discount, current	4,875	0
Operating lease liabilities, current	626	957
Finance lease liabilities, current	1,644	0
Total current liabilities	32,617	18,309
Convertible notes, net of unamortized discount, non-current	35,066	45,049
Operating lease liabilities, non-current	498	1,443
Finance lease liabilities, non-current	18,988	0
Other liabilities	136	23
Total liabilities	87,305	64,824
Commitments and contingencies (Note 12)
Stockholders' equity:
Common stock, $0.01 par value, 120,000,000 shares authorized; 60,996,367 and 54,773,061 shares issued and 60,996,367 and 54,769,030 shares outstanding at December 31, 2020 and December 31, 2019, respectively	610	548
Treasury stock, at cost, 0 and 4,031 common shares at December 31, 2020 and December 31, 2019, respectively	0	(53)
Additional paid-in capital	825,794	489,925
Accumulated other comprehensive income (loss)	(42)	20
Accumulated deficit	(322,843)	(183,143)
Total stockholders' equity	503,519	307,297
Total liabilities and stockholders' equity	590,824	372,121
Series A Convertible Preferred Shares [Member]
Stockholders' equity:
Preferred stock	0	0
Series B Convertible Preferred Shares [Member]
Stockholders' equity:
Preferred stock	$ 0	$ 0