Acquisition of Confluence - Summary of fair value consideration (Details) - USD ($) $ in Thousands	1 Months Ended	9 Months Ended
Aug. 31, 2017	Sep. 30, 2017
Fair value of consideration
Cash consideration paid		$ 9,647
Confluence
Business Acquisition [Line Items]
Additional contingent consideration based on milestones, maximum, per Agreement	$ 80,000
Additional contingent consideration based on milestones, portion payable in shares	$ 2,500
Royalty term	10 years
Fair value of consideration
Cash consideration paid	$ 10,269
Aclaris common stock issued	9,675
Contingent consideration	4,378
Total fair value of consideration to Confluence equity holders	$ 24,322

Amount recognized from contingent consideration in a business combination.

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- Definition

In a business combination, the portion of the maximum contingent consideration based upon achievement of certain milestones which is payable in shares of the acquiror's stock.

+ References

No definition available.

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- Definition

In a business combination, the maximum contingent consideration to be paid based upon achievement of certain milestones as set forth in the Agreement and Plan of Merger.

+ References

No definition available.

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The period of time for which royalties are to be paid per the Agreement and Plan of Merger

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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.

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- Definition

Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
-Paragraph 8
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-SubTopic 30
-Section 30
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- Definition

Amount of equity interests of the acquirer, including instruments or interests issued or issuable in consideration for the business combination.

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- Definition

The cash outflow associated with the acquisition of a business, net of the cash acquired from the purchase.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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