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LICENSES AND AGREEMENTS (Details) - USD ($) $ in Thousands	1 Months Ended			3 Months Ended			6 Months Ended		12 Months Ended	15 Months Ended	18 Months Ended
LICENSES AND AGREEMENTS (Details) - USD ($) $ in Thousands	Apr. 17, 2017	Nov. 30, 2016	Aug. 31, 2011	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2020	Jun. 30, 2020	May 31, 2017
Research and development expenses				$ 49,274		$ 39,298	$ 106,226	$ 70,203
Research and Development Arrangement
Prepaid expense, current												$ 1,400
Research Collaboration And Clinical Grant Agreement
Research and development expenses				100		200	300	500
Research Collaboration And Clinical Grant Agreements With Moffitt
Research and development expenses						400	200	1,600
Maximum \| Research and Development Arrangement
Research and development arrangement, contract to perform for others, costs incurred, gross	$ 14,200
National Cancer Institute
Research and development expenses							$ 500
Moffitt License Agreement
Agreement term							20 years
Novartis Pharma AG - License Agreement [Member]
Research and development expenses					$ 10,000		$ 10,000
Cooperative Research and Development Agreement
Agreement term			5 years
Research and development expenses										$ 500	$ 1,000
WuXi Apptech, Inc - Manufacturing and Services Agreement
Research and development expenses				5,700		$ 6,800	12,300	$ 10,700
WuXi Apptech, Inc - Manufacturing and Services Agreement \| Manufacturing Suites
Manufacturing and services agreement, amount payable		$ 1,200
WuXi Apptech, Inc - Manufacturing and Services Agreement \| Commercial Manufacturing cGMP Suite
Manufacturing and services agreement, amount payable		$ 2,700
Moffitt License Agreement Two
Research and development expenses										100	100
Payments for upfront licensing fee									$ 100
Additional milestone payable				400			400			$ 400	$ 400
Moffitt License Agreement One
Payments for upfront licensing fee							100
Cellectis S.A
Research and development expenses				$ 100			$ 200