Lease Base Rent

No definition available.

Name:	hyln_LeaseBaseRent
Namespace Prefix:	hyln_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Lessee Lease Renewal Option Number

+ References

No definition available.

+ Details

Name:	hyln_LesseeLeaseRenewalOptionNumber
Namespace Prefix:	hyln_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Lessee, Operating Lease, Extended Term of Contract

+ References

No definition available.

+ Details

Name:	hyln_LesseeOperatingLeaseExtendedTermOfContract
Namespace Prefix:	hyln_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

- Definition

Lessee, Operating Lease, Renewal Rent Abatement Term

+ References

No definition available.

+ Details

Name:	hyln_LesseeOperatingLeaseRenewalRentAbatementTerm
Namespace Prefix:	hyln_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

- Definition

Operating Lease, Tenant Improvement Allowance

+ References

No definition available.

+ Details

Name:	hyln_OperatingLeaseTenantImprovementAllowance
Namespace Prefix:	hyln_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Area of a real estate property.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 275
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482861/275-10-50-2

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 970
-SubTopic 360
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-28(Column A)(Footnote 2))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478979/970-360-S99-1

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 970
-SubTopic 360
-Name Accounting Standards Codification
-Section 30
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478150/970-360-30-2

+ Details

Name:	us-gaap_AreaOfRealEstateProperty
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:areaItemType
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 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478964/842-20-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 7A
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478964/842-20-50-7A

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478964/842-20-50-3

+ Details

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

- Definition

Term of lessee's operating lease renewal, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478964/842-20-50-3

+ Details

Name:	us-gaap_LesseeOperatingLeaseRenewalTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of sublease income excluding finance and operating lease expense.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 53
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479589/842-20-55-53

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478964/842-20-50-4

+ Details

Name:	us-gaap_SubleaseIncome
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis=hyln_CedarParkMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis=hyln_CedarParkSubleaseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Leases (Details) ft² in Thousands, $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended
Leases (Details) ft² in Thousands, $ in Millions	Aug. 11, 2026 USD ($) ft² option	Jun. 30, 2026 USD ($)	Jun. 30, 2025 USD ($)	Jun. 30, 2026 USD ($)	Jun. 30, 2025 USD ($)
Lessee, Lease, Description [Line Items]
Sublease operating income		$ 0.1	$ 0.1	$ 0.2	$ 0.1
Cedar Park \| Subsequent Events
Lessee, Lease, Description [Line Items]
Area of real estate property \| ft²	125
Lessee operating lease term of contract	63 months
Lease base rent	$ 9.8
Rent abatement period	3 months
Tenant improvement allowance	$ 0.6
Number of renewal options \| option	2
Lease term	5 years
Cedar Park Sublease \| Subsequent Events
Lessee, Lease, Description [Line Items]
Area of real estate property \| ft²	27