LICENSE AGREEMENTS (Details) € in Thousands, $ in Thousands	1 Months Ended			6 Months Ended
	Sep. 30, 2016 USD ($)	Aug. 31, 2016 USD ($)	Jun. 30, 2016 USD ($) option	Jun. 30, 2020 USD ($)	Jun. 30, 2020 EUR (€)
Organization And Basis Of Presentation [Line Items]
Royalty rate				2.00%	2.00%
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%
University of Zurich | Collaborative Arrangement, Revenue Based on Clinical Development Milestone
Organization And Basis Of Presentation [Line Items]
License agreement, amount payable upon achievement of specified milestone				$ 750
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
License Agreement, royalty payment, reduction, conditions not met				1.50%	1.50%
License maintenance fees | €					€ 50
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%
Roche
Organization And Basis Of Presentation [Line Items]
Up-front license fee		$ 7,500
Additional up-front fee		262,500
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 | First Indication
Organization And Basis Of Presentation [Line Items]
License agreement, amount payable upon achievement of specified milestone		197,500
Roche | Collaborative Arrangement, Revenue Based on Development Milestone
Organization And Basis Of Presentation [Line Items]
License agreement, amount payable upon achievement of specified milestone		72,500
Roche | Collaborative Arrangement, Revenue Based on Regulatory Milestone
Organization And Basis Of Presentation [Line Items]
License agreement, amount payable upon achievement of specified milestone		50,000
Roche | Collaborative Arrangement, Revenue Based on Commercialization Milestone
Organization And Basis Of Presentation [Line Items]
License agreement, amount payable upon achievement of specified milestone		$ 75,000
Roche | Second Indication
Organization And Basis Of Presentation [Line Items]
License agreement, amount payable upon achievement of specified milestone				$ 65,000
Roche | EBI-031 | Minimum
Organization And Basis Of Presentation [Line Items]
Royalty rate				7.50%	7.50%
Roche | EBI-031 | Maximum
Organization And Basis Of Presentation [Line Items]
Royalty rate				15.00%	15.00%
Roche | EBI-031 | Collaborative Arrangement, Revenue Based on Development Milestone
Organization And Basis Of Presentation [Line Items]
License agreement, amount payable upon achievement of specified milestone	$ 22,500
Roche | IL-6
Organization And Basis Of Presentation [Line Items]
Royalty rate				50.00%	50.00%