The period of written notice before termination of agreement.

No definition available.

Name:	acrs_CollaborativeAgreementPeriodForNoticeOfTermination
Namespace Prefix:	acrs_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum aggregate payments owed upon achievement of specified pre-commercialization milestones under the terms of the agreement.

+ References

No definition available.

+ Details

Name:	acrs_CollaborativeArrangementsMaximumAdditionalPaymentsOwedUponAchievementOfSecondSetOfDevelopmentMilestones
Namespace Prefix:	acrs_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Maximum aggregate payments owed upon achievement of specified pre-commercialization milestones under the terms of the agreement, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	acrs_CollaborativeArrangementsMaximumAggregatePaymentsOwedUponAchievementOfSpecifiedPreCommercializationMilestones
Namespace Prefix:	acrs_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Period from the first commercial product sale that royalties are owed, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	acrs_CollaborativeArrangementsPeriodFromFirstCommercialProductSaleRoyaltiesAreOwed
Namespace Prefix:	acrs_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount that the entity will pay the Licensors as an annual license maintenance fee, which is offset by any milestone payments or royalties paid during that year.

+ References

No definition available.

+ Details

Name:	acrs_LicenseArrangementAnnualMaintenanceFee
Namespace Prefix:	acrs_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The minimum period before expiration of the agreement, starting from agreememt effective date.

+ References

No definition available.

+ Details

Name:	acrs_TermOfAgreementMinimum
Namespace Prefix:	acrs_
Data Type:	xbrli:durationItemType
Balance Type:	na
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

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

- Definition

The cash outflow to acquire asset without physical form usually arising from contractual or other legal rights, excluding goodwill.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3213-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Investing Activities
-URI http://asc.fasb.org/extlink&oid=6516133

+ Details

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

- Definition

The aggregate costs incurred (1) in a planned search or critical investigation aimed at discovery of new knowledge with the hope that such knowledge will be useful in developing a new product or service, a new process or technique, or in bringing about a significant improvement to an existing product or process; or (2) to translate research findings or other knowledge into a plan or design for a new product or process or for a significant improvement to an existing product or process whether intended for sale or the entity's use, during the reporting period charged to research and development projects, including the costs of developing computer software up to the point in time of achieving technological feasibility, and costs allocated in accounting for a business combination to in-process projects deemed to have no alternative future use.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 730
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6420194&loc=d3e21568-108373

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 985
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6501960&loc=d3e128462-111756

+ Details

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

- Details

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

- Details

Name:	us-gaap_ProductOrServiceAxis=acrs_A101ProductMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_CounterpartyNameAxis=acrs_RigelPharmaceuticalsIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ProductOrServiceAxis=acrs_JakInhibitorsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_CounterpartyNameAxis=acrs_JakpharmAndKeyOrganicsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ProductOrServiceAxis=acrs_ProductsContainingSpecifiedCompoundsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Agreements Related to Intellectual Property (Details) - USD ($) $ in Thousands		1 Months Ended			12 Months Ended
	Aug. 27, 2015	Feb. 29, 2016	Nov. 30, 2015	Aug. 31, 2012	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
License Agreement
Upfront payment recorded as research and development expense					$ 15,339	$ 6,507	$ 3,488
Assignment Agreement and Finder's Services Agreement [Member] \| A-101
License Agreement
Milestone payment		$ 300					$ 400
Maximum aggregate payments owed upon achievement of specified pre-commercialization milestones					1,000
Maximum additional payments owed upon achievement of second set of development milestones					4,500
Term of Agreeement, Minimum				15 years
License and collaboration agreement \| Rigel \| JAK inhibitors
License Agreement
Maximum aggregate payments owed upon achievement of specified pre-commercialization milestones	$ 80,000
Maximum additional payments owed upon achievement of second set of development milestones	$ 10,000
Upfront payment recorded as research and development expense					8,000
Period from first commercial product sale that royalties are owed (in years)	10 years
Commercial License Agreement \| JAKPharm and Key Organics [Member] \| Products Containing Specified Compounds [Member]
License Agreement
Maximum aggregate payments owed upon achievement of specified pre-commercialization milestones			$ 2,350
Upfront payment recorded as research and development expense					$ 250
Period from first commercial product sale that royalties are owed (in years)			10 years
Written termination notice period			3 months
Annual maintenance fee			$ 50