Long-Term Debt - 2026 Capped Calls (Details) - 2026 Capped Calls $ / shares in Units, $ in Millions	6 Months Ended
Jun. 30, 2021 USD ($) $ / shares shares
Debt Instrument [Line Items]
Aggregate number of common shares subject to capped calls \| shares	28,675,900
Initial strike price	$ 6.97
Initial cap price	$ 8.42
Aggregate cost of capped call transactions \| $	$ 10.6

Aggregate cost for capped call transactions in connection with issuance of convertible debt instruments.

No definition available.

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Namespace Prefix:	hlx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Cap price stated in the contract for options indexed to the issuer's equity shares.

+ References

No definition available.

+ Details

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Namespace Prefix:	hlx_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- 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

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

- Definition

The number of issuer's shares to which the option contract is indexed.

+ References

+ Details

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

- Definition

Exercise or strike price stated in the contract for options indexed to the issuer's equity shares.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 40
-Section 50
-Paragraph 5
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=120519210&loc=d3e90205-114008

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 480
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (f)(1)
-URI http://asc.fasb.org/extlink&oid=109262807&loc=d3e22047-110879

+ Details

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Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Details

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Data Type:	na
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