LICENSE AGREEMENTS (Details) $ in Thousands		3 Months Ended	12 Months Ended
	Jun. 10, 2016 USD ($) option indication	Sep. 15, 2016 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2019 EUR (€)
University of Zurich
Organization And Basis Of Presentation [Line Items]
License agreement, royalty on net product sales, percentage			4.00%	4.00%
License agreement, rate requiring reduction in the amount of royalties owed			10.00%	10.00%
License agreement, royalty on net product sales, minimum			2.00%	2.00%
Roche
Organization And Basis Of Presentation [Line Items]
License agreement, up-front fee	$ 7,500
License agreement, additional up-front fee	$ 262,500
License agreement, number of unrelated Indications | indication	2
License agreement, option periods | option	2
License agreement, buyout amount under first option period	$ 135,000
License agreement, period to pay buyout option once exercised	30 days
License agreement, buyout amount under second option period	$ 265,000
License agreement, buyout amount under second option period, upon non-issuance of patent rights or licensed product	$ 220,000
License agreement, period for termination where sufficient development activities are not performed	12 months
Roche | EBI-031 | Minimum
Organization And Basis Of Presentation [Line Items]
License agreement, royalty rate	7.50%
Roche | EBI-031 | Maximum
Organization And Basis Of Presentation [Line Items]
License agreement, royalty rate	15.00%
Roche | IL-6
Organization And Basis Of Presentation [Line Items]
License agreement, royalty rate	50.00%
Micromet AG
Organization And Basis Of Presentation [Line Items]
License agreement, royalty on net product sales, percentage			3.50%	3.50%
Potential milestone payments | €				€ 3,600,000
License Agreement, royalty payment, reduction, conditions not met			1.50%	1.50%
License maintenance fees | €				€ 50,000
XOMA Ireland Limited
Organization And Basis Of Presentation [Line Items]
License agreement, amount payable upon achievement of specified milestone			$ 250
License agreement, royalty on net product sales, percentage			2.50%	2.50%
License agreement, rate requiring reduction in the amount of royalties owed			50.00%	50.00%
License agreement, royalty on net product sales, minimum			1.75%	1.75%
Collaborative Arrangement, Revenue Based on Clinical Development Milestone | University of Zurich
Organization And Basis Of Presentation [Line Items]
License agreement, amount payable upon achievement of specified milestone			$ 750
First Indication | Roche
Organization And Basis Of Presentation [Line Items]
License agreement, amount payable upon achievement of specified milestone	$ 197,500
Collaborative arrangement, revenue based on development milestone | Roche
Organization And Basis Of Presentation [Line Items]
License agreement, amount payable upon achievement of specified milestone	72,500
Collaborative arrangement, revenue based on development milestone | Roche | EBI-031
Organization And Basis Of Presentation [Line Items]
License agreement, amount payable upon achievement of specified milestone		$ 22,500
Collaborative arrangement, revenue based on regulatory milestone | Roche
Organization And Basis Of Presentation [Line Items]
License agreement, amount payable upon achievement of specified milestone	50,000
Collaborative arrangement, revenue based on commercialization milestone | Roche
Organization And Basis Of Presentation [Line Items]
License agreement, amount payable upon achievement of specified milestone	75,000
Second Indication | Roche
Organization And Basis Of Presentation [Line Items]
License agreement, amount payable upon achievement of specified milestone	$ 65,000