FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS - Summarized Financial Data (Details) - USD ($) $ in Thousands	6 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Balance Sheet Information
Current assets			$ 342,058	$ 431,234
Current liabilities			6,110	5,371
Income Statement Information
Total revenue			336,794	261,016	$ 261,004
Loss from operations			321,123	246,360	238,251
Net (income) loss			$ 293,814	$ 190,993	$ 406,328
Armata
Balance Sheet Information
Current assets	$ 17,024	$ 17,024
Noncurrent assets	28,651	28,651
Current liabilities	7,070	7,070
Noncurrent liabilities	13,986	13,986
Income Statement Information
Total revenue		319
Loss from operations		(15,134)
Net (income) loss		(15,557)
Entasis
Balance Sheet Information
Current assets	68,398	68,398
Noncurrent assets	1,564	1,564
Current liabilities	6,862	6,862
Noncurrent liabilities	864	$ 864
Income Statement Information
Loss from operations	(26,080)
Net (income) loss	$ (24,529)