Quarterly report pursuant to Section 13 or 15(d)

Basis of Presentation - Additional Information (Details)

Basis of Presentation - Additional Information (Details)			3 Months Ended		12 Months Ended
	Apr. 30, 2020 USD ($)	Jan. 21, 2020 USD ($) Debtinstrument shares	Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)	Jul. 16, 2019 USD ($)
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Net losses			$ 16,100,000	$ 20,580,000	$ 103,130,000
Accumulated deficit			$ 251,023,000		$ 234,923,000
Subsequent Event \| Iterum Therapeutics US Limited \| Silicon Valley Bank (SVB) \| Paycheck Protection Program
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Aggregate principal amount	$ 700,000
Debt instrument interest rate	1.00%
Debt instrument maturity period	2 years
Minimum percentage of loan proceeds used for payroll costs	75.00%
Debt instrument, description	Under the terms of the agreement, there shall be no payments due by the Company during 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 note on the last day of the Deferral Period by the maturity date. Under the terms of the Program, the SBA will forgive the portion of loan proceeds used for payroll costs and other designated operating expenses for up to eight weeks, provided at least 75% of the loan proceeds are used for payroll costs. The Company expects to incur qualifying payroll costs and other operating expenses in the eight weeks from April 30, 2020 such that the Company may be able to request forgiveness of some portion of the loan from the Lender.
Maximum
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Aggregate initial offering price of securities authorized to issue						$ 150,000,000
Private Placement \| 2025 Exchangeable Notes
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Aggregate principal amount		$ 51,600,000
Debt instrument interest rate		6.50%
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 value		$ 160,000
Debt instrument, aggregate potential payment capped rate		4,000 times
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%
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%
Private Placement \| Securities
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Debt instrument price per unit		$ 1,000
Debt instrument, shares embedded within each unit, shares \| shares		1,000
Debt instrument, shares embedded within each unit, value		$ 1,000
Proceeds from sale of securities		$ 46,400,000