The equity interest of shareholders, partners or other equity holders in consolidated entity.

No definition available.

Name:	erna_BeneficialOwnershipPercentageOfIssuedAndOutstandingShares
Namespace Prefix:	erna_
Data Type:	dtr-types:percentItemType
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Period Type:	instant

- Definition

Number of shares of stock issued during the period pursuant to equity line of credit consideration shares.

+ References

No definition available.

+ Details

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

- Definition

The number of shares to be issued by the subsidiary or equity method investee per stock transaction.

+ References

No definition available.

+ Details

Name:	erna_SaleOfStockNumberOfSharesToIssuedInTransaction
Namespace Prefix:	erna_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

+ Details

Name:	erna_StandbySecuritiesPurchaseAgreementAbstract
Namespace Prefix:	erna_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The cash inflow from the issuance of common stock, preferred stock, treasury stock, stock options, and other types of equity.

+ 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

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.6-03(i)(1))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479886/946-10-S99-3

+ Details

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

- Definition

The number of shares issued or sold by the subsidiary or equity method investee per stock transaction.

+ References

No definition available.

+ Details

Name:	us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of stock repurchase plan authorized.

+ References

No definition available.

+ Details

Name:	us-gaap_StockRepurchaseProgramAuthorizedAmount1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=erna_StandbyEquityPurchaseAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Equity and Warrants, SEPA (Details) - USD ($) $ in Millions		12 Months Ended
Equity and Warrants, SEPA (Details) - USD ($) $ in Millions	Apr. 05, 2023	Dec. 31, 2023	Apr. 30, 2023
Lincoln Park Capital Fund, LLC [Member]
Standby Securities Purchase Agreement [Abstract]
Common stock shares issued and sold (in shares)		214,000
Gross proceeds from sale of equity		$ 0.3
Lincoln Park Capital Fund, LLC [Member] \| Maximum [Member]
Standby Securities Purchase Agreement [Abstract]
Aggregate gross purchase price	$ 10.0		$ 10.0
Beneficial owning percentage on issued and outstanding shares	4.99%
Standby Equity Purchase Agreement [Member]
Standby Securities Purchase Agreement [Abstract]
Common stock shares issued and sold (in shares)		214,000
Gross proceeds from sale of equity		$ 0.3
Number of remaining shares to be sold (in shares)		2,860,000
Standby Equity Purchase Agreement [Member] \| Lincoln Park Capital Fund, LLC [Member]
Standby Securities Purchase Agreement [Abstract]
Consideration shares of common stock (in shares)	74,000