Description of Business and Basis of Financial Statements (Details) $ in Thousands, € in Millions						9 Months Ended		18 Months Ended
	Apr. 27, 2020 USD ($)	Apr. 23, 2020 USD ($) shares	Apr. 12, 2019 shares	Apr. 11, 2019 USD ($) shares	Apr. 11, 2019 EUR (€) shares	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)
Business Acquisition [Line Items]
Accumulated deficit | $						$ 92,769		$ 92,769	$ 59,911
Proceeds from issuance of private placement | $								208,600
Cash and cash equivalents | $						133,183		$ 133,183	$ 29,369
Conversion ratio			0.025
Vital Therapies, Inc.
Business Acquisition [Line Items]
Percentage of shares owned			11.75%
Immunic AG
Business Acquisition [Line Items]
Percentage of shares owned			88.25%
Vital Therapies, Inc. | Immunic AG
Business Acquisition [Line Items]
Exchange ratio				17.17	17.17
Immunic AG | Vital Therapies, Inc.
Business Acquisition [Line Items]
Aggregate consideration issuable (in shares)			8,927,130
Shares owned prior to transaction (in shares)			1,059,269
Immunic AG | Restricted Stock Units | Vital Therapies, Inc.
Business Acquisition [Line Items]
RSUs owned prior to transaction (in shares)			127,500	5,100,000	5,100,000
Private Placement | Immunic AG
Business Acquisition [Line Items]
Shares issued in private placement transaction (in shares)				2,197,742	2,197,742
Aggregate consideration from private placement				$ 29,900	€ 26.7
April 2020 Equity Issuances
Business Acquisition [Line Items]
Proceeds from issuance of common stock | $	$ 13,900	$ 15,000				$ 13,918	$ 0
Shares issued in private placement transaction (in shares)		1,764,706