| Cover | Dec. 15, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K/A |
| Amendment Flag | true |
| Amendment Description | On December 15, 2021, Assertio Holdings, Inc. (the "Company") filed a Current Report on Form 8-K (the "Original Report") with the Securities and Exchange Commission to report the Company's consummation of the transaction (the "Transaction") contemplated by the Asset Purchase Agreement dated December 15, 2021 by and among the Company, Otter Pharmaceuticals, LLC and Antares Pharma, Inc. ("Antares"). |
| Document Period End Date | Dec. 15, 2021 |
| Entity File Number | 001-39294 |
| Entity Registrant Name | ASSERTIO HOLDINGS, INC. |
| Entity Central Index Key | 0001808665 |
| Entity Tax Identification Number | 85-0598378 |
| Entity Incorporation, State or Country Code | DE |
| Entity Address, Address Line One | 100 South Sanders Rd |
| Entity Address, Address Line Two | Suite 300 |
| Entity Address, City or Town | Lake Forest |
| Entity Address, State or Province | IL |
| Entity Address, Postal Zip Code | 60045 |
| City Area Code | 224 |
| Local Phone Number | 419-7106 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, $0.0001 par value |
| Trading Symbol | ASRT |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
