Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 232,694	$ 297,098
Investments	156,046	185,621
Prepaid expenses and other current assets	3,319	4,626
Total current assets	392,059	487,345
Property and equipment, net	22,299	19,206
Goodwill	30,815	30,815
Restricted cash	1,343	1,568
Deposits	455	455
Operating lease right-of-use assets	1,569	914
Finance lease right-of-use asset	48,480	50,521
Total assets	497,020	590,824
Current liabilities:
Accounts payable and accrued expenses	19,615	25,472
Convertible notes, net of unamortized discount, current	0	4,875
Operating lease liabilities, current	863	626
Finance lease liability, current	1,689	1,644
Total current liabilities	22,167	32,617
Convertible notes, net of unamortized discount, non-current	0	35,066
Operating lease liabilities, non-current	905	498
Finance lease liability, non-current	19,144	18,988
Other liabilities	80	136
Total liabilities	42,296	87,305
Commitments and contingencies (Note 12)
Stockholders' equity:
Common stock, $0.01 par value, 120,000,000 shares authorized; 64,505,889 and 60,996,367 shares issued and outstanding at December 31, 2021 and 2020, respectively	645	610
Additional paid-in capital	946,152	825,794
Accumulated other comprehensive loss	(161)	(42)
Accumulated deficit	(491,912)	(322,843)
Total stockholders' equity	454,724	503,519
Total liabilities and stockholders' equity	497,020	590,824
Series A Convertible Preferred Stock [Member]
Stockholders' equity:
Preferred stock	0	0
Series B Convertible Preferred Stock [Member]
Stockholders' equity:
Preferred stock	$ 0	$ 0