The number of warrants issued during the period.

No definition available.

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- Definition

The cash outflow for cost incurred directly with the issuance of a private placement.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
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Period Type:	duration

- Definition

The cash outflow for cost incurred directly with the issuance of a Registered direct offering.

+ References

No definition available.

+ Details

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

- Definition

The cash inflow associated with the amount received from private placement, net of stock issuance costs.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
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Period Type:	duration

- Definition

The cash inflow associated with the amount received from entity's Registered direct offering of stock to the public.

+ References

No definition available.

+ Details

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

- Definition

The cash inflow associated with the amount received from entity's Registered direct offering of stock, net of stock issuance costs.

+ References

No definition available.

+ Details

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

- Definition

The amount of remaining committed funding to be received from investors.

+ References

No definition available.

+ Details

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

- Definition

The number of shares agreed to issue or sell by the subsidiary or equity method investee per stock transaction.

+ References

No definition available.

+ Details

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Namespace Prefix:	tmc_
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Period Type:	instant

- Definition

Number of new stock issued for private placement during the period.

+ References

No definition available.

+ Details

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Namespace Prefix:	tmc_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of share issued under Registered direct offering during the period.

+ References

No definition available.

+ Details

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Namespace Prefix:	tmc_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of securities into which the class of warrant or right may be converted. For example, but not limited to, 500,000 warrants may be converted into 1,000,000 shares.

+ 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

+ Details

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

- Definition

The cash inflow associated with the amount received from entity's raising of capital via private rather than public placement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 45
-Paragraph 14
-Subparagraph (a)
-SubTopic 10
-Topic 230
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-14

+ Details

Name:	us-gaap_ProceedsFromIssuanceOfPrivatePlacement
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Cash received on stock transaction after deduction of issuance costs.

+ References

No definition available.

+ Details

Name:	us-gaap_SaleOfStockConsiderationReceivedOnTransaction
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Per share or per unit amount of equity securities issued.

+ References

No definition available.

+ Details

Name:	us-gaap_SharesIssuedPricePerShare
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

No definition available.

+ Details

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

- Details

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- Details

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Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_StatementEquityComponentsAxis=us-gaap_CommonStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

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Namespace Prefix:
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- Details

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Financing Activity (Details) - USD ($) $ / shares in Units, $ in Thousands			12 Months Ended
	Jun. 16, 2025	May 12, 2025	Dec. 31, 2025	Dec. 31, 2024	Feb. 06, 2025
Financing Activity
Gross proceeds from registered direct offerings			$ 42,000	$ 23,900
Expenses paid for registered direct offering			734	$ 357
Gross proceeds from private placement			85,118
Agreement with Korea Zinc
Financing Activity
Number of shares agreed to sell and issue	19,623,376
Purchase price per share	$ 4.34
Gross proceeds from private placement	$ 85,200		$ 85,200
Warrants to purchase an aggregate of common shares	6,868,181		6,868,181
Issuance of shares to Korea Zinc (in shares)			19,623,376
Total expenses related to agreement paid in equity			$ 1,900
Class B Warrants
Financing Activity
Number of warrants issued			2,500,000	7,450,000
Class C Warrants
Financing Activity
Number of warrants issued			12,333,333
Common Shares
Financing Activity
Number of issuance of shares under Registered Direct Offering (in shares)				19,400,000
Issuance of shares to Korea Zinc (in shares)			19,623,376
2024 Registered Direct Offering
Financing Activity
Remaining committed fund					$ 5,000
Net proceeds from Registered Direct Offering			$ 5,000
2024 Registered Direct Offering \| Class B Warrants
Financing Activity
Number of shares agreed to sell and issue					2,500,000
Purchase price per share				$ 1
Net proceeds from Registered Direct Offering			2,800
2024 Registered Direct Offering \| Common Shares
Financing Activity
Number of shares agreed to sell and issue				19,900,000	5,000,000
Net proceeds from Registered Direct Offering			$ 2,200
Number of issuance of shares under Registered Direct Offering (in shares)			5,000,000	14,900,000
2024 Registered Direct Offering \| Common Shares \| Class B Warrants
Financing Activity
Number of shares agreed to sell and issue				9,950,000
2025 Registered Direct Offering
Financing Activity
Gross proceeds from issuance		$ 37,000
Gross proceeds from registered direct offerings			$ 37,000
Number of issuance of shares under Registered Direct Offering (in shares)			12,333,333
Expenses paid for registered direct offering			$ 300
Net proceeds			$ 36,700
2025 Registered Direct Offering \| Class C Warrants
Financing Activity
Purchase price per share		$ 3
Number of warrants issued		12,333,333	12,333,333
2025 Registered Direct Offering \| Common Shares
Financing Activity
Number of shares agreed to sell and issue		12,333,333
Number of issuance of shares under Registered Direct Offering (in shares)			12,333,333
2025 Registered Direct Offering \| Common Shares \| Class C Warrants
Financing Activity
Number of shares agreed to sell and issue		12,333,333