The adjustment to lease liability and right of use asset due to remeasurement in noncash financing activities.

No definition available.

Name:	erna_AdjustmentToLeaseLiabilityAndRightOfUseAssetDueToRemeasurement
Namespace Prefix:	erna_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of operating lease expense to be paid for the month of February, March, April or May 2024 including share amounts related to property taxes and common area maintenance costs.

+ References

No definition available.

+ Details

Name:	erna_OperatingLeaseExpenseToBePaid
Namespace Prefix:	erna_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Weighted average incremental borrowing rate for operating lease calculated at point in time.

+ References

No definition available.

+ Details

Name:	erna_OperatingLeaseIncrementalBorrowingRate
Namespace Prefix:	erna_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The percentage increase in base rent per year after first year for operating leases.

+ References

No definition available.

+ Details

Name:	erna_OperatingLeasesIncreaseInBaseRentPercentage
Namespace Prefix:	erna_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of rental expense payable per month for operating leases.

+ References

No definition available.

+ Details

Name:	erna_OperatingLeasesMonthlyBaseRent
Namespace Prefix:	erna_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The company incurred additional out-of-pocket expenses for sublessor/lessor owned assets.

+ References

No definition available.

+ Details

Name:	erna_OutOfPocketExpenses
Namespace Prefix:	erna_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of tenant improvement allowance received.

+ References

No definition available.

+ Details

Name:	erna_ReceivedAmountOfTenantImprovementAllowance
Namespace Prefix:	erna_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of tenant improvement allowance to improvements of the Premises.

+ References

No definition available.

+ Details

Name:	erna_TenantImprovementAllowance
Namespace Prefix:	erna_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of tenant improvement allowance per rentable square foot for the improvements of premises.

+ References

No definition available.

+ Details

Name:	erna_TenantImprovementAllowancePerRentableSquareFoot
Namespace Prefix:	erna_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The company has to pay sublease for owned assets.

+ References

No definition available.

+ Details

Name:	erna_UnpaidOutOfPocketCostsTenantImprovementAllowance
Namespace Prefix:	erna_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Area of a real estate property.

+ References

No definition available.

+ Details

Name:	us-gaap_AreaOfRealEstateProperty
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:areaItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount before accumulated depreciation of additions or improvements to assets held under a lease arrangement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 360
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482099/360-10-50-1

+ Details

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

- References

No definition available.

+ Details

Name:	us-gaap_LesseeOperatingLeaseDescriptionAbstract
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

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

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-SubTopic 10
-Topic 210
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16)(a)(2))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479440/944-210-S99-1

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479853/942-210-S99-1

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
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- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=erna_ERSquibbSonsLLCMember
Namespace Prefix:
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LEASES, Operating Lease (Details)	1 Months Ended		3 Months Ended		12 Months Ended
LEASES, Operating Lease (Details)	Feb. 29, 2024 USD ($)	Oct. 31, 2022 USD ($) ft²	Mar. 31, 2024 USD ($)	Mar. 31, 2023 USD ($)	Dec. 31, 2023	May 03, 2024 USD ($)
Operating Leases [Abstract]
Area of premises \| ft²		45,500
Letter of credit		$ 4,100,000
Out-of-pocket expenses	$ 400,000
Unpaid out of pocket costs	$ 600,000
Incremental borrowing rate	11.10%				14.40%
Adjustment to lease liability and ROU asset due to remeasurement	$ 4,200,000		$ 4,245,000	$ 0
Subsequent Event [Member]
Operating Leases [Abstract]
Past due rent amount						$ 2,300,000
E.R. Squibb & Sons, L.L.C. [Member]
Operating Leases [Abstract]
Area of premises \| ft²		45,500
Extension term of sublease			5 years
Monthly base rent payable		$ 500,000
Percentage increase in base rent after first year		3.00%
Letter of credit		$ 4,100,000
Tenant improvement allowance per rentable square foot		190
Tenant improvement allowance		8,600,000
Cost improvement		$ 1,600,000
Company received tenant improvement allowance			$ 8,600,000