CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) Non-Cash Activities - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Other Significant Noncash Transactions [Line Items]
Unrealized (loss) gain on available-for-sale securities	$ (39)	$ 451
Net change in accounts payable and accrued expenses related to purchases of property and equipment	(1,849)	(892)
Common Stock Issued to Board of Directors and Scientific Advisory Board that was Earned and Accrued for in Previous Period [Member]
Other Significant Noncash Transactions [Line Items]
Other significant noncash transaction, value of consideration received	$ 300	$ 300