Summary of Significant Accounting Policies - Additional Information (Details)

v3.20.2

Summary of Significant Accounting Policies - Additional Information (Details) $ / shares in Units, € in Thousands, $ in Thousands	9 Months Ended
	Sep. 30, 2020 USD ($) Segment $ / shares	Sep. 30, 2020 EUR (€)	Dec. 31, 2019 $ / shares
Accounting Policies [Line Items]
Ordinary shares, par value \| $ / shares	$ 0.01		$ 0.01
Number of business segments \| Segment	1
June 3 SPA
Accounting Policies [Line Items]
Warrants to purchase ordinary shares, exercise price \| $ / shares	$ 0.01
June 30 SPA
Accounting Policies [Line Items]
Warrants to purchase ordinary shares, exercise price \| $ / shares	$ 0.01
Certificates Of Deposit
Accounting Policies [Line Items]
Restricted cash	$ 90
Warrants Issued \| June 3 SPA
Accounting Policies [Line Items]
Restricted cash	17
Warrants Issued \| June 30 SPA
Accounting Policies [Line Items]
Restricted cash	19
Maximum
Accounting Policies [Line Items]
Cash, FDIC insured amount	250
Cash, DGS insured amount	$ 117	€ 100

- Definition

Accounting policies.

+ References

No definition available.

+ Details

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Namespace Prefix:	itrm_
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Balance Type:	na
Period Type:	duration

- Definition

Cash Deposit Guarantee Scheme insured amount.

+ References

No definition available.

+ Details

Name:	itrm_CashDGSInsuredAmount
Namespace Prefix:	itrm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of cash deposited in financial institutions as of the balance sheet date that is insured by the Federal Deposit Insurance Corporation.

+ References

No definition available.

+ Details

Name:	us-gaap_CashFDICInsuredAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Exercise price per share or per unit of warrants or rights outstanding.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Face amount or stated value per share of common stock.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

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Balance Type:	na
Period Type:	instant

- Definition

Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8672-108599

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of cash restricted as to withdrawal or usage. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=121583591&loc=SL98516268-108586

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(1)(a))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(2))
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

+ Details

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Namespace Prefix:	us-gaap_
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Balance Type:	debit
Period Type:	instant

- Details

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Namespace Prefix:
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Period Type:

- Details

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- Details

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Namespace Prefix:
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Period Type:

- Details

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Namespace Prefix:
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- Details

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Namespace Prefix:
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Period Type:

Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies - Additional Information (Details)