CONSOLIDATED STATEMENT OF STOCKHOLDERS' EQUITY (Parenthetical) $ in Thousands	9 Months Ended
Sep. 30, 2017 USD ($)
IPO
Underwriting discounts, commissions, and offering costs incurred	$ 5,352
Private Placement
Underwriting discounts, commissions, and offering costs incurred	$ 691

The amount of expense incurred for costs associated with the issuance of common stock.

No definition available.

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