Liabilities for additional milestone payment.

No definition available.

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Namespace Prefix:	alrn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Number of additional milestones achieved.

+ References

No definition available.

+ Details

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- Definition

Payments for milestone.

+ References

No definition available.

+ Details

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Balance Type:	credit
Period Type:	duration

- Definition

Amount of contractual obligation, including but not limited to, long-term debt, capital lease obligations, operating lease obligations, purchase obligations, and other commitments.

+ References

No definition available.

+ Details

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Balance Type:	credit
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- Definition

The aggregate costs related to goods produced and sold and services rendered by an entity during the reporting period. This excludes costs incurred during the reporting period related to financial services rendered and other revenue generating activities.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 924
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 11.L)
-URI http://asc.fasb.org/extlink&oid=6472922&loc=d3e499488-122856

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.2(a),(d))
-URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227

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Balance Type:	debit
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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Balance Type:	na
Period Type:	duration

- Definition

The amount of cash paid for royalties during the current period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 25
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3536-108585

+ Details

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

- Details

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- Details

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Commitments and Contingencies - Additional Information (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) Milestone	Jun. 30, 2019 USD ($)	Feb. 28, 2010 USD ($)	Dec. 31, 2006 USD ($)
Harvard and Dana-Farber Agreement [Member]
Other Commitments [Line Items]
Milestone payments	$ 0	$ 0	$ 0	$ 0
Additional milestones achieved \| Milestone			0
Additional liabilities for milestone payments	0		$ 0
Payments for royalties			0
Harvard and Dana-Farber Agreement [Member] \| Therapeutic Product [Member]
Other Commitments [Line Items]
Aggregate milestones payments					$ 7,700,000
Harvard and Dana-Farber Agreement [Member] \| Diagnostic Product [Member]
Other Commitments [Line Items]
Aggregate milestones payments					$ 700,000
Harvard and Dana-Farber Agreement [Member] \| License [Member]
Other Commitments [Line Items]
Annual license maintenance fees			145,000	145,000
Umicore Agreement [Member]
Other Commitments [Line Items]
Aggregate milestones payments						$ 6,400,000
Milestone payments	0	$ 0	$ 0	0
Additional milestones achieved \| Milestone			0
Additional liabilities for milestone payments	$ 0		$ 0
Umicore Agreement [Member] \| License [Member]
Other Commitments [Line Items]
Annual license maintenance fees			50,000	$ 50,000
Umicore Agreement [Member] \| License and Maintenance [Member]
Other Commitments [Line Items]
Annual license maintenance fees			$ 50,000