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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

STOCKHOLDERS' EQUITY - 2018 Stock grant agreements (Details) - Nonemployees - shares	1 Months Ended		12 Months Ended
	Sep. 30, 2018	Aug. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Individual with stock grant agreement with issuance at IPO
Share-Based Compensation Awards
Issuance of common stock to nonemployees (in shares)	96,000
Researchers, Employees of MSK
Share-Based Compensation Awards
Issuance of common stock to nonemployees (in shares)		448,000	448,000	448,000	448,000	560,000