Equity Compensation Plans - Narrative (Details)	3 Months Ended
	Mar. 31, 2021 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Description	The Company has the Seelos Therapeutics, Inc. Amended and Restated 2012 Stock Long Term Incentive Plan (the "2012 Plan"), which provides for the issuance of incentive and non-incentive stock options, restricted and unrestricted stock awards, stock unit awards and stock appreciation rights. Options and restricted stock units granted generally vest over a period of one to four years and have a maximum term of ten years from the date of grant. As of March 31, 2021, an aggregate of 10,878,019 shares of common stock were authorized under the 2012 Plan, of which 1.6 million shares of common stock were available for future grants. Upon completion of the Merger, the Company assumed the Seelos Therapeutics, Inc. 2016 Equity Incentive Plan (the "2016 Plan") and awards outstanding under the 2016 Plan became awards for common stock. Effective as of the Merger, no further awards may be issued under the 2016 Plan. During the three months ended March 31, 2021, the Company's Board of Directors awarded a performance stock unit award to the Company's CEO for 2,400,000 shares of common stock. Vesting of this award is subject to the Company achieving certain performance criteria established at the grant date and the individual fulfilling a service condition (continued employment). As of March 31, 2021, none of the performance conditions had been satisfied. The Company does not believe that the achievement of the performance criteria is probable at this time and therefore has not recognized any compensation expense during the three months ended March 31, 2021. Compensation expense will be recognized only once the performance condition is probable of being achieved and only for the cumulative amount related to the service condition that has been fulfilled. On May 15, 2020, the Company's stockholders approved the Company's 2020 Employee Stock Purchase Plan (the "ESPP"), whereby qualified employees are allowed to purchase limited amounts of the Company's common stock at the lesser of 85% of the market price at the beginning or end of the offering period. The stockholders have authorized an initial amount of 1.0 million shares for purchase by employees under the ESPP. The ESPP provides that an additional number of shares will automatically be added annually to the shares authorized for issuance under the ESPP on January 1st of each year commencing on January 1, 2021 and ending on (and including) January 1, 2030, which amount shall be equal to the lesser of (i) 1% of the number of shares of the Company's common stock issued and outstanding on the immediately preceding December 31, and (ii) a number of shares of common stock set by the Company's Board of Directors or the Compensation Committee of the Board of Directors (the "Compensation Committee") of the Company on or prior to each such January 1. During the three months ended March 31, 2021, the Company sold 40,518 shares of common stock under the ESPP. On July 28, 2019, the Compensation Committee of the Board of Directors (the "Compensation Committee") of the Company adopted the Seelos Therapeutics, Inc. 2019 Inducement Plan (the "2019 Inducement Plan"), which became effective on August 12, 2019. The 2019 Inducement Plan provides for the grant of equity-based awards in the form of stock options, stock appreciation rights, restricted stock, unrestricted stock, stock units, including restricted stock units, performance units and cash awards, solely to prospective employees of the Company or an affiliate of the Company provided that certain criteria are met. Awards under the 2019 Inducement Plan may only be granted to an individual, as a material inducement to such individual to enter into employment with the Company, who (i) has not previously been an employee or director of the Company or (ii) is rehired following a bona fide period of non-employment with the Company. The maximum number of shares available for grant under the 2019 Inducement Plan is 1,000,000 shares of the Company's common stock. The 2019 Inducement Plan is administered by the Compensation Committee and expires on August 12, 2029.
Stock options exercisable (shares)	683,000
Stock options exercised (shares)	(30,000)
Weighted average exercise price per share | $ / shares	$ 4.11