Stock-Based Compensation Plans - Additional Information (Details)									1 Months Ended	3 Months Ended		9 Months Ended		48 Months Ended
	Sep. 30, 2025 USD ($) $ / shares shares	Jul. 07, 2025 tranche $ / shares shares	Jun. 04, 2025 shares	Mar. 04, 2024 $ / shares shares	Jan. 08, 2024	Jun. 28, 2023 shares	Aug. 01, 2021 shares	Apr. 25, 2021 shares	Jul. 31, 2019 shares	Sep. 30, 2025 USD ($) $ / shares shares	Sep. 30, 2024 USD ($)	Sep. 30, 2025 USD ($) $ / shares shares	Sep. 30, 2024 USD ($) $ / shares	Dec. 31, 2023 shares	Sep. 30, 2017 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options repriced (in shares)				3,317,596
Stock-based compensation, exercise price (in usd per share) \| $ / shares				$ 1.72
Share-based payment arrangement \| $												$ 1,200,000
Repricing cost during the period \| $										$ 0	$ 86,000	$ 100,000	$ 1,000,000
Expected dividend yield				0.00%	0.00%							0.00%
Options exercisable (in shares)		5,000,000
Series A Warrants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options exercisable (in shares)		10,000,000
Options issued (in shares)		86,666,667
Grant-date fair value (in usd per share) \| $ / shares	$ 0.326									$ 0.326		$ 0.326
Series B Warrants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options exercisable (in shares)		10,000,000
Options issued (in shares)		86,666,667
Grant-date fair value (in usd per share) \| $ / shares	0.394									0.394		0.394
January 2024 Pre-Funded Warrants \| Tranche 2
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options exercisable (in shares)		5,000,000
Options issued (in shares)		46,620,046
Grant-date fair value (in usd per share) \| $ / shares	0.013									0.013		0.013
January 2024 Pre-Funded Warrants \| Tranche 3
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options exercisable (in shares)		5,000,000
Options issued (in shares)		46,620,046
Grant-date fair value (in usd per share) \| $ / shares	$ 0.013									0.013		0.013
SARs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield	0.00%	0.00%
Authorized (in shares)		35,000,000
Options exercisable, ending balance (in usd per share) \| $ / shares		$ 0.765
Number of tranches \| tranche		5
Grant-date fair value (in usd per share) \| $ / shares	$ 0.404									$ 0.404		$ 0.404
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term of options (in years)				4 years 7 months 28 days	4 years 9 months 21 days
Exercised (in usd per share) \| $ / shares				$ 3.00
Maximum \| SARs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term of options (in years)	2 years 9 months 18 days	2 years 10 months 24 days
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term of options (in years)				1 year 7 months 28 days	1 year 9 months 21 days
Exercised (in usd per share) \| $ / shares				$ 1.72
Minimum \| SARs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term of options (in years)	10 months 24 days	1 year
2021 Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum annual contributions per employee (as a percent)								15.00%
Purchase price of the stock, at discount from market price at purchase date (as a percent)								85.00%
Shares available for grant (in shares)				1,200,000				200,000
Additional shares authorized (in shares)				1,000,000
Shares issued under the ESPP (in shares)							491,839
Share-based compensation expense \| $										$ 22,000	24,000	$ 70,000	$ 24,000
2019 Omnibus Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for grant (in shares)									1,500,000
Expected term of options (in years)												5 years 10 months 28 days	5 years 11 months 12 days
Expected dividend yield												0.00%	0.00%
Options granted in period, weighted-average grant date fair value (in usd per share) \| $ / shares												$ 0.67	$ 0.99
Total unrecognized compensation expense \| $	$ 13,900,000									13,900,000		$ 13,900,000
Period over which compensation cost will be recognized (in years)												3 years
2019 Omnibus Equity Incentive Plan \| Incentive stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (in years)												4 years
2019 Omnibus Equity Incentive Plan \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term of options (in years)												10 years
2019 Omnibus Equity Incentive Plan \| Maximum \| Non-statutory options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (in years)												4 years
2019 Omnibus Equity Incentive Plan \| Minimum \| Non-statutory options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (in years)												3 years
2019 Omnibus Equity Incentive Plan, Evergreen Provision
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional shares authorized (in shares)									4,900,000					4,408,871
Additional shares authorized (as a percent)									4.00%
Increase in other share (in shares)			7,000,000	9,100,000		4,440,000
SARs Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense \| $										1,500,000		$ 1,500,000
Total unrecognized compensation expense \| $	$ 7,800,000									$ 7,800,000		$ 7,800,000
Period over which compensation cost will be recognized (in years)												1 year 3 months 21 days
2014 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for grant (in shares)	0									0		0
2017 Inducement Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for grant (in shares)															46,250
Share-based compensation expense \| $										$ 0	$ 0	$ 0	$ 0

IMMUNIC, INC. 10-Q