CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Current assets
Cash and cash equivalents	$ 44,626	$ 40,833
Marketable securities (current)	265,813	275,340
Restricted cash (current)	16,216	25,032
Accounts receivable, net	168	978
Inventories	2,735	2,751
Prepaid expenses and other current assets	5,861	6,857
Total current assets	335,419	351,791
Property, plant and equipment, net	156,896	139,141
Long-term marketable securities	32,724	64,396
Long-term restricted cash	70,238	70,168
Operating right-of-use assets	2,209	2,414
Finance right-of-use assets	26,887	27,297
Intangible assets, net	8,656	8,938
Deposits and other assets	5,631	2,331
Total assets	638,660	666,476
Current liabilities
Accounts payable and accrued liabilities	13,410	28,288
Operating lease liabilities (current)	416	772
Finance lease liabilities (current)	4,029	3,413
Loans payable - other (current)	89	158
Total current liabilities	17,944	32,631
2021 Bonds payable (long-term)	66,669	66,486
Loans payable - other (long-term)	276	318
Operating lease liabilities (long-term)	1,838	1,902
Finance lease liabilities (long-term)	17,403	17,797
Other long-term liabilities	95	87
Total liabilities	104,225	119,221
Stockholders' Equity
Common stock, $0.01 par value per share; 500,000,000 and 250,000,000 shares authorized at March 31, 2022 and December 31, 2021, respectively; 201,752,722 and 201,988,662 shares issued and outstanding at March 31, 2022 and December 31, 2021, respectively.	2,019	2,020
Additional paid-in capital	1,107,051	1,103,224
Accumulated other comprehensive loss	(1,587)	(614)
Accumulated deficit	(573,048)	(557,375)
Total stockholders' equity	534,435	547,255
Total liabilities and stockholders' equity	$ 638,660	$ 666,476
Common stock, shares authorized (in shares)	500,000,000	250,000,000