License, Research and Collaboration Agreements - Biogen Agreement - Additional Information (Details) $ in Millions	12 Months Ended
Dec. 31, 2020 USD ($)
Biogen
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Additional payments based on the successful achievement of future regulatory or sales milestones	$ 300
Alkermes License Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Cost Of License Payable	$ 15

Carrying value as of the balance sheet date of obligations incurred and payable for cost directly related to generating license revenue. Licensing arrangements include, but are not limited to, rights to use a patent, copyright, technology, manufacturing process, software or trademark.

No definition available.

Name:	acor_CostOfLicensePayable
Namespace Prefix:	acor_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant