Number of warrants or rights are exercised.

No definition available.

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Period Type:	duration

- Definition

The number of warrants issued during the period.

+ References

No definition available.

+ Details

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Data Type:	xbrli:sharesItemType
Balance Type:	na
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- Definition

The amount of expenses associated with warrant issuance.

+ References

No definition available.

+ Details

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Namespace Prefix:	tmc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of increase in additional paid in capital (APIC) resulting from the issuance of warrants. Includes allocation of proceeds of debt securities issued with detachable stock purchase warrants.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-2

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 505
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-Name Accounting Standards Codification
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-Paragraph 1
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-Publisher FASB
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Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 505
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-Name Accounting Standards Codification
-Section S50
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480070/505-10-S50-1

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 25
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481284/470-20-25-2

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-3

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
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-Name Accounting Standards Codification
-Section S50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480738/235-10-S50-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
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-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(4))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

+ Details

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

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-3

+ Details

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

- Definition

Number of securities into which each warrant or right may be converted. For example, but not limited to, each warrant may be converted into two shares.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of warrants or rights outstanding.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Value of outstanding derivative securities that permit the holder the right to purchase securities (usually equity) from the issuer at a specified price.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)(i)
-Publisher FASB
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Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

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Period Type:	instant

- Details

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Namespace Prefix:
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- Details

Name:	us-gaap_ClassOfWarrantOrRightAxis=tmc_ClassBWarrantsMember
Namespace Prefix:
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Balance Type:
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- Details

Name:	us-gaap_ClassOfWarrantOrRightAxis=tmc_ClassCWarrantsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ClassOfWarrantOrRightAxis=tmc_KoreaZincWarrantsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ClassOfWarrantOrRightAxis=tmc_NauruWarrantsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ClassOfWarrantOrRightAxis=tmc_TongaWarrantsMember
Namespace Prefix:
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Warrants - Class A, Class B, Class C, Korea Zinc, Nauru and Tonga Warrants (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025	Dec. 31, 2025
Warrants
Additional paid-in capital, warrant issued		$ 33,079	$ 43,176	$ 33,079
Nauru warrant cost		$ 33,079		$ 33,079
Class A Warrants
Warrants
Number of warrants outstanding	4,317,500		4,317,500		4,317,500
Exercise price of warrants	$ 2		$ 2
Warrants exercised			0
Value of outstanding warrants	$ 3,600		$ 3,600		$ 3,600
Number of shares issuable per warrant	1		1
Class B Warrants
Warrants
Number of warrants outstanding	15,000		15,000		15,000
Exercise price of warrants	$ 2		$ 2
Warrants exercised	0		0
Value of outstanding warrants	$ 9		$ 9		$ 9
Number of shares issuable per warrant	1		1
Class C Warrants
Warrants
Number of warrants outstanding	10,003,333		10,003,333		10,003,333
Exercise price of warrants	$ 4.5		$ 4.5
Warrants exercised	0		0
Value of outstanding warrants	$ 10,200		$ 10,200		$ 10,200
Number of shares issuable per warrant	1		1
Korea Zinc Warrants
Warrants
Exercise price of warrants	$ 7		$ 7
Warrants exercised	0		0
Value of outstanding warrants	$ 11,500		$ 11,500		$ 11,500
Warrants issued			6,868,181		6,868,181
Nauru Warrants
Warrants
Number of warrants outstanding	9,146,268		9,146,268		9,146,268
Exercise price of warrants	$ 4.72		$ 4.72
Warrants exercised			0
Value of outstanding warrants	$ 33,100		$ 33,100		$ 33,100
Tonga Warrants
Warrants
Exercise price of warrants	$ 5.87		$ 5.87
Warrants exercised	0		0
Value of outstanding warrants	$ 5,000		$ 5,000		$ 5,000
Warrants issued			1,000,000		1,000,000