Quarterly report pursuant to Section 13 or 15(d)

Debt - Additional Information (Details)

Debt - Additional Information (Details)						1 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended	32 Months Ended
Debt - Additional Information (Details)	Jun. 05, 2023 USD ($) $ / shares shares	Sep. 08, 2020 USD ($) Debtinstrument $ / shares	Apr. 30, 2020 USD ($)	Jan. 21, 2020 USD ($) Debtinstrument shares	Apr. 27, 2018 USD ($) $ / shares shares	Dec. 31, 2020 USD ($)	Nov. 30, 2020 USD ($)	Sep. 30, 2023 USD ($) $ / shares shares	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($) $ / shares shares	Sep. 30, 2022 USD ($)	Dec. 31, 2020 USD ($)	Sep. 30, 2023 USD ($) $ / shares shares	Mar. 01, 2022
Debt Instrument [Line Items]
Accretion of debt discounts and deferred financing costs										$ 1,753,000	$ 1,748,000
Ordinary Shares
Debt Instrument [Line Items]
Number of warrants to purchase preferred shares \| shares					1,326			1,326		1,326			1,326
Loan and Security Agreement \| Silicon Valley Bank (SVB)
Debt Instrument [Line Items]
Loan and security agreement entered date										Apr. 27, 2018
Funded amount under agreement					$ 15,000,000
Remaining borrowing facility available date					Oct. 31, 2019
Maximum amount available under agreement					$ 30,000,000
Date of first required payment of initial draw					Nov. 01, 2019
Minimum fixed interest rate per annum					8.31%
Final interest rate payment on outstanding principal					4.20%
Principal and interest payment, maturity date					Mar. 01, 2022
Final payment fee					$ 630,000
Principal payment during the period										$ 1,552,000
Effective annual interest rate on outstanding debt														12.51%
Interest expense								$ 0	$ 0	$ 0	16,000
Accretion of debt discounts and deferred financing costs									0		6,000
Loan and Security Agreement \| Silicon Valley Bank (SVB) \| Wall Street Journal Prime Rate
Debt Instrument [Line Items]
Basis spread on interest rate					3.89%
Loan and Security Agreement \| Silicon Valley Bank (SVB) \| Maximum
Debt Instrument [Line Items]
Maximum amount available under second draw					$ 15,000,000
Silicon Valley Bank and Life Sciences Fund II LLC \| Series B Convertible Preferred Shares
Debt Instrument [Line Items]
Number of warrants to purchase preferred shares \| shares					19,890			19,890		19,890			19,890
Warrants to purchase preferred shares, exercise price \| $ / shares					$ 282.75			$ 282.75		$ 282.75			$ 282.75
2025 Exchangeable Notes
Debt Instrument [Line Items]
Interest expense								$ 205,000	205,000	$ 615,000	615,000
Accretion of debt discounts and deferred financing costs								591,000	591,000	1,753,000	1,753,000
Aggregate principal amount				$ 9,891,000
Debt instrument, outstanding principal								12,607,000		$ 12,607,000			$ 12,607,000
Debt instrument, payment terms										The Company will be required to pay each holder of the Exchangeable Notes the greater of three times the outstanding principal amount of such Exchangeable Note and the consideration that would be received by the holder of such Exchangeable Note in connection with such Fundamental Change if the holder had exchanged its note for ordinary shares immediately prior to the consummation of such Fundamental Change, plus any accrued and unpaid interest.
Fair value of derivative liability				27,038,000
Fair value of derivative liability related to rights offering		$ 82,000
Financing transaction costs												$ 2,848,000
Financing transaction costs, capitalized						$ 2,814,000						$ 2,814,000
2025 Exchangeable Notes \| Private Placement
Debt Instrument [Line Items]
Aggregate principal amount				51,588,000
Debt instrument price per unit		1,000		1,000
Aggregate principal amount								39,201,000		$ 39,201,000			$ 39,201,000
Notes exchanged for ordinary shares \| shares													3,592,555
Debt instrument, outstanding principal								12,607,000		12,607,000			$ 12,607,000
2025 Exchangeable Notes \| Private Placement and Rights Offering
Debt Instrument [Line Items]
Aggregate principal amount		$ 220,000		$ 51,800,000
Debt instrument interest rate				6.50%
RLNs \| Private Placement
Debt Instrument [Line Items]
Aggregate principal amount				$ 103,000
Number of debt instruments within each notes \| Debtinstrument		50		50
RLNs \| Private Placement and Rights Offering
Debt Instrument [Line Items]
Aggregate principal amount		$ 500		$ 100,000
Securities \| Private Placement
Debt Instrument [Line Items]
Debt instrument price per unit		1,000		$ 1,000
Debt instrument, shares embedded within each unit, shares \| shares	89.9035			66.666
Debt instrument, shares embedded within each unit, value	$ 1,000	$ 1,000
Debt instrument, shares embedded within each unit, exchange price \| $ / shares	$ 11.123	$ 15
Paycheck Protection Program \| Silicon Valley Bank (SVB) \| Iterum Therapeutics US Limited
Debt Instrument [Line Items]
Interest expense								0	0	$ 0	0
Aggregate principal amount			$ 744,000
Debt instrument interest rate			1.00%
Debt instrument maturity period			2 years
Debt instrument, description										Under the terms of the agreement, there were no payments due by the Company until the SBA remitted the forgiveness amount to Iterum US Limited or until after the 10 months after the end of the six-month period beginning April 30, 2020 (the Deferral Period). Following the Deferral Period, equal monthly repayments of principal and interest were due to fully amortize the principal amount outstanding on the PPP loan by the maturity date.
Debt instrument, forgiveness loan							$ 340,000
Debt instrument, remaining amount amortized						$ 404,000
Debt Instrument, principal repayments								$ 0	$ 0	$ 0	$ 69,000