Asset transfer and license agreement termination notice period if bankruptcy petition filed.

No definition available.

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- Definition

Asset transfer and license agreement termination period after written notice.

+ References

No definition available.

+ Details

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- Definition

Asset transfer and license agreement termination period notice of failure.

+ References

No definition available.

+ Details

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- Definition

Milestone payment.

+ References

No definition available.

+ Details

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

- Definition

Obligation to payment upon maximum achievement of certain clinical and commercial milestones.

+ References

No definition available.

+ Details

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- Definition

Operating lease liability percentage.

+ References

No definition available.

+ Details

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Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of rent expense incurred for leased assets, including but not limited to, furniture and equipment, that is not directly or indirectly associated with the manufacture, sale or creation of a product or product line.

+ References

No definition available.

+ Details

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

- Definition

Remaining lease term of operating lease, 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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI https://asc.fasb.org/extlink&oid=128292326&loc=SL77918673-209980

+ Details

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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

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- Details

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- Details

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- Details

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- Details

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Commitments and Contingencies - Additional Information (Details) - USD ($)	1 Months Ended	3 Months Ended		6 Months Ended
	Apr. 30, 2018	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Loss Contingencies [Line Items]
Operating leases, rent expense		$ 47,000	$ 72,000	$ 100,000	$ 100,000
Remaining lease term		6 months		6 months
Incremental borrowing rate used to determine operating lease liability percentage				4.25%
Teva Agreement
Loss Contingencies [Line Items]
Payment upon achievement of certain clinical and commercial milestones	$ 135,000,000.0
Asset transfer and license agreement, termination period after written notice				120 days
Asset transfer and license agreement, termination period notice of breach				60 days
Asset transfer and license agreement termination notice period if bankruptcy petition filed				60 days
Teva Agreement \| Research and Development Expenses
Loss Contingencies [Line Items]
Milestone payments		$ 0	$ 0	$ 0	$ 0
Teva Agreement \| Teva's GlycoPEGylated FGF21 Program
Loss Contingencies [Line Items]
Payment upon achievement of certain clinical and commercial milestones	67,500,000
Teva Agreement \| Teva's Development Program
Loss Contingencies [Line Items]
Payment upon achievement of certain clinical and commercial milestones	$ 67,500,000