Quarterly report pursuant to Section 13 or 15(d)

Basis of Presentation - Additional Information (Details)

Basis of Presentation - Additional Information (Details)		3 Months Ended		9 Months Ended		12 Months Ended
	Jan. 21, 2020 USD ($) Debtinstrument	Sep. 30, 2022 USD ($) $ / shares	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($) $ / shares	Sep. 30, 2021 USD ($)	Dec. 31, 2021 USD ($) $ / shares	Aug. 17, 2022 $ / shares shares	Feb. 03, 2021 $ / shares	Jan. 28, 2021 $ / shares	Sep. 08, 2020 USD ($)	Apr. 30, 2020 USD ($)
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Net losses		$ 29,109,000	$ (3,741,000)	$ 39,344,000	$ 87,382,000	$ 91,564,000
Accumulated deficit		417,837,000		417,837,000		378,493,000
Cash and cash equivalents		20,489,000		20,489,000		$ 27,446,000
Short-term investments		$ 43,834,000		$ 43,834,000
Description of reverse share split				The Company's shareholders approved a reverse share split of the Company's ordinary shares on June 15, 2022, which became effective on August 17, 2022, (the Reverse Share Split). As of 5:00 p.m. Eastern Standard Time on August 17, 2022, every fifteen ordinary shares of $0.01 each (nominal value) in the authorized and unissued and authorized and issued share capital of the Company were consolidated into one ordinary share of $0.15 each (nominal value), and the nominal value of each ordinary share was subsequently reduced from $0.15 to $0.01 nominal value per share.
Ordinary shares, par value \| $ / shares		$ 0.01		$ 0.01		$ 0.01	$ 0.01		$ 0.01
Reverse share split previous nominal value \| $ / shares							$ 0.15
0.01 Nominal Value
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Common Stock, shares authorized and unissued \| shares							15
Ordinary shares, par value \| $ / shares							$ 0.01
0.15 Nominal Value
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Common stock, shares authorized and issued \| shares							1
Ordinary shares, par value \| $ / shares							$ 0.15
Iterum Therapeutics US Limited \| Silicon Valley Bank (SVB) \| Paycheck Protection Program
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Aggregate principal amount											$ 744,000
Debt instrument interest rate											1.00%
2025 Exchangeable Notes
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Aggregate principal amount		$ 12,607,000		$ 12,607,000
Private Placement and Rights Offering \| 2025 Exchangeable Notes
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Aggregate principal amount										$ 51,808,000
Debt instrument interest rate	6.50%
Private Placement and Rights Offering \| RLNs
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Aggregate principal amount	$ 104,000
Private Placement \| 2025 Exchangeable Notes
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Aggregate principal amount	51,588,000
Debt instrument price per unit	1,000
Private Placement \| RLNs
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Aggregate principal amount	$ 103,000
Number of debt instruments within each notes \| Debtinstrument	50
October Offering
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Ordinary shares, par value \| $ / shares		$ 0.01		$ 0.01
February Underwritten Offering \| Underwriting Agreement
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Ordinary shares, par value \| $ / shares								$ 0.01