INCOME TAXES - Provision for income taxes (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
INCOME. TAXES.
Loss before income taxes, as reported in the consolidated statements of operations	$ (348,101,000)	$ (279,381,000)	$ (172,871)
Computed "expected" tax benefit	(73,101,000)	(58,670,000)	(36,303)
Increase (decrease) in income taxes resulting from:
Expected benefit from state and local taxes	(3,445,000)	(10,801,000)	(2,128)
Research and development credits	(8,337,000)	(5,265,000)	(7,266)
Other	867,000	1,065,000	641
Stock awards	(6,726,000)	(1,558,000)	1,292
Enactment of federal tax reform	0	(14,763,000)	0
Change in the balance of the valuation allowance for deferred tax assets	90,742,000	89,992,000	43,764
Income Tax Expense (Benefit)	$ 0	$ 0	$ 0