ACQUISITIONS - Acquisition Date Fair Value of Consideration Transferred (Details) - Spectrum Pharmaceuticals, Inc. - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	Jul. 31, 2023	Sep. 30, 2023
Business Acquisition [Line Items]
Assertio shares issued (in shares)	38,013
Assertio closing price per share as of the Effective Date (in dollars per share)	$ 5.69
Fair value of Assertio shares issued	$ 216,294
Repayment of Spectrum's long-term debt	32,647
CVRs	3,932	$ 0
Consideration transferred	$ 252,873

Number of shares of equity interests issued or issuable to acquire entity.

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