Nature of Operations and Basis of Presentation - Additional Information (Details)

v3.20.4

Nature of Operations and Basis of Presentation - Additional Information (Details)													1 Months Ended			3 Months Ended								12 Months Ended
	Nov. 02, 2020 USD ($) $ / shares shares	Oct. 31, 2020 $ / shares shares	Oct. 27, 2020 USD ($) $ / shares shares	Oct. 22, 2020 $ / shares shares	Jul. 02, 2020 $ / shares shares	Jun. 05, 2020 $ / shares shares	Jun. 03, 2020 USD ($) $ / shares shares	Apr. 30, 2020 USD ($)	Jan. 21, 2020 USD ($) Debtinstrument $ / shares shares	Jun. 26, 2018 USD ($) $ / shares shares	May 30, 2018 USD ($) $ / shares shares	May 15, 2018 $ / shares	Dec. 31, 2020 USD ($) $ / shares shares	Nov. 30, 2020 USD ($)	Jun. 30, 2020 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) $ / shares shares	Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($) $ / shares shares	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($) $ / shares shares	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2020 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($)	Jul. 16, 2019 USD ($)	Mar. 13, 2018 $ / shares shares	Mar. 12, 2018 $ / shares	Feb. 16, 2018 $ / shares	May 18, 2017 $ / shares	Nov. 18, 2015 $ / shares	Oct. 14, 2015 $ / shares shares
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Reverse share split												0.0636
Share consolidation basis nominal value per share | $ / shares												$ 0.01571
Share consolidation basis, Renominalisation value per share | $ / shares												$ 0.01
Net proceeds from issuance of stock after deducting underwriting discounts,commissions and offering cost																								$ 24,926,000	$ 3,037,000	$ 1,362,000
Description of deferring payment on US payroll taxes																								In April 2020, the Company began deferring payment on its share of U.S. payroll taxes owed, as allowed by the Coronavirus Aid, Relief and Economic Security Act (CARES Act) through December 31, 2020. The Company is able to defer half of its share of U.S. payroll taxes owed until December 31, 2021, with the remaining half due on December 31, 2022
Ordinary shares, shares issued | shares													49,431,028			49,431,028				14,868,973				49,431,028	14,868,973			413,110					413,110
Ordinary shares, par value | $ / shares											$ 0.01		$ 0.01			$ 0.01				$ 0.01				$ 0.01	$ 0.01			$ 0.001	$ 0.0001	$ 0.01	$ 0.01	$ 0.01	$ 0.01
Proceeds from registered direct offerings, net of transaction costs																								$ 32,200,000
Net losses																$ 11,186,000	$ 12,199,000	$ 12,521,000	$ 16,100,000	$ 23,641,000	$ 31,271,000	$ 27,638,000	$ 20,580,000	52,006,000	$ 103,130,000	77,056,000
Accumulated deficit													$ 286,929,000			286,929,000				234,923,000				286,929,000	234,923,000
Cash and cash equivalents													$ 14,508,000			$ 14,508,000				$ 4,801,000				14,508,000	$ 4,801,000
Net proceeds from underwritten public offering																								$ 42,096,000
Underwritten public offering closing date																								Feb. 08, 2021
Registered direct offering closing date																								Feb. 12, 2021
Exercise of underwriters option in full to purchase additional shares closing date																								Feb. 10, 2021
June 3 SPA
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Ordinary shares, par value | $ / shares													$ 0.01			$ 0.01								$ 0.01
June 30 SPA
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Ordinary shares, par value | $ / shares													$ 0.01			0.01								$ 0.01
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%
Debt instrument maturity period								2 years
Debt instrument, description								Under the terms of the agreement, there shall be no payments due by the Company until the SBA remits the forgiveness amount to the borrower or 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 will be due to fully amortize the principal amount outstanding on the PPP loan by the maturity date																Under the terms of the agreement, there shall be no payments due by the Company until after the Deferral Period. Following the Deferral Period, equal monthly repayments of principal and interest will be 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											$ 404,000
Debt Instrument, equal monthly repayments													$ 26,000											$ 26,000
Maximum
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Aggregate initial offering price of securities authorized to issue																											$ 150,000,000
Private Placement and Rights Offering | 2025 Exchangeable Notes
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Aggregate principal amount									$ 51,800,000
Debt instrument interest rate									6.50%
Private Placement and Rights Offering | RLNs
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Aggregate principal amount									$ 100,000
IPO
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of shares issued | shares										200,000	6,150,000
Offering price per share | $ / shares										$ 13.00	$ 13.00
Net proceeds from issuance of stock after deducting underwriting discounts,commissions and offering cost										$ 2,400,000	$ 71,800,000															$ 74,153,000
Private Placement | June 3 SPA
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of warrants to purchase ordinary shares | shares						208,023
Warrants to purchase ordinary shares, exercise price | $ / shares						$ 2.1031	$ 1.62
Warrants expiry date						Jun. 03, 2025	Dec. 05, 2025
Warrants closing date							Jun. 05, 2020
Percentage of ordinary shares issued to purchase warrants						7.00%
Private Placement | June 30 SPA
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of warrants to purchase ordinary shares | shares					236,088
Warrants to purchase ordinary shares, exercise price | $ / shares					$ 1.8531										$ 1.42			$ 1.42
Warrants expiry date					Jun. 30, 2025										Jan. 02, 2026
Warrants closing date															Jul. 02, 2020
Percentage of ordinary shares issued to purchase warrants					7.00%
Private Placement | Maximum | June 3 SPA
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of warrants to purchase ordinary shares | shares							1,485,885
Private Placement | Maximum | June 30 SPA
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of warrants to purchase ordinary shares | shares															1,686,343			1,686,343
Private Placement | 2025 Exchangeable Notes
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Aggregate principal amount									51,600,000
Debt instrument price per unit									1,000
Private Placement | RLNs
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Aggregate principal amount									$ 100,000
Number of debt instruments within each notes | Debtinstrument									50
Debt instrument, aggregate potential payment capped rate									4,000 times
Private Placement | Securities
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Debt instrument, shares embedded within each unit, shares | shares	1,286.1845								1,000
Debt instrument, shares embedded within each unit, value	$ 1,000								$ 1,000
Rights Offering in Connection with Private Placement
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Maximum subscription units to be accepted | shares									220
Rights Offering in Connection with Private Placement | 2025 Exchangeable Notes
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Aggregate principal amount									$ 200,000
Debt instrument price per unit									1,000
Debt instrument price per unit									$ 1,000
Debt instrument, shares embedded within each unit, shares | shares	1,286.1845								1,000
Debt instrument, shares embedded within each unit, value	$ 1,000,000								$ 1,000
Debt instrument, shares embedded within each unit, exchange price | $ / shares	$ 0.7775								$ 1.00
Rights Offering in Connection with Private Placement | RLNs
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Aggregate principal amount									$ 20,000
Number of debt instruments within each notes | Debtinstrument									50
Aggregate amount payable per unit									$ 160.00
Debt instrument, aggregate potential payment capped rate									4,000 times
Rights Offering in Connection with Private Placement | RLNs | Minimum
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Debt instrument, percentage of net revenue from domestic sale for potential aggregate payments									15.00%
Rights Offering in Connection with Private Placement | RLNs | Maximum
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Debt instrument, percentage of net revenue from domestic sale for potential aggregate payments									20.00%
Rights Offering in Connection with Private Placement | Securities
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Proceeds from sale of securities									$ 45,000,000
Direct Offering | June 3 SPA
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Offering price per share | $ / shares							$ 1.6825
Ordinary shares, shares issued | shares							2,971,770
Ordinary shares, par value | $ / shares							$ 0.01
Aggregate gross proceeds from ordinary shares							$ 5,000,000
Proceeds from registered direct offerings, net of transaction costs							$ 4,300,000
Direct Offering | June 30 SPA
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Offering price per share | $ / shares															$ 1.4825			$ 1.4825
Ordinary shares, shares issued | shares															3,372,686			3,372,686
Ordinary shares, par value | $ / shares															$ 0.01			$ 0.01
Aggregate gross proceeds from ordinary shares															$ 5,000,000
Proceeds from registered direct offerings, net of transaction costs															$ 4,200,000
October Offering
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Ordinary shares, shares issued | shares			15,511,537
Ordinary shares, par value | $ / shares			$ 0.01										$ 0.01			$ 0.01								$ 0.01
Aggregate gross proceeds from ordinary shares			$ 17,400,000
Proceeds from registered direct offerings, net of transaction costs			$ 15,500,000																					$ 900,000
Number of warrants to purchase ordinary shares | shares		1,884,615											1,268,859			1,268,859								1,268,859
Warrants to purchase ordinary shares, exercise price | $ / shares		$ 0.8125	$ 0.65
Warrants expiry date		Oct. 22, 2025	Oct. 27, 2025
Percentage of ordinary shares issued to purchase warrants		7.00%
October Offering | Pre-Funded Warrants
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Offering price per share | $ / shares			$ 0.01
Proceeds from registered direct offerings, net of transaction costs																								$ 110,000
Number of warrants to purchase ordinary shares | shares			11,411,539
Warrants to purchase ordinary shares, exercise price | $ / shares			$ 0.64
Percentage of ordinary share at election of purchaser			9.99%
October Offering | Warrant
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Offering price per share | $ / shares			$ 0.65
Number of warrants to purchase ordinary shares | shares			20,192,307
Warrants to purchase ordinary shares, exercise price | $ / shares			$ 0.65
October Offering | Purchase Agreement
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of warrants to purchase ordinary shares | shares				1,884,615
Warrants to purchase ordinary shares, exercise price | $ / shares				$ 0.8125
Warrants expiry date				Oct. 22, 2025
Percentage of ordinary shares issued to purchase warrants				7.00%
Description of purchase agreement																								In connection with the October Offering, the Company entered into a Securities Purchase Agreement (the Purchase Agreement) on October 22, 2020 with certain institutional investors. The Purchase Agreement contains customary representations and warranties of the Company, termination rights of the parties, and certain indemnification obligations of the Company and ongoing covenants of the Company, including a prohibition on the Company entering into variable rate transactions for a period of 12 months after the closing of the October Offering, subject to certain exceptions
October Offering | Minimum | Pre-Funded Warrants
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Percentage of outstanding ordinary shares			4.99%
October Offering | Maximum
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of warrants to purchase ordinary shares | shares			20,192,307