Nature of Business and Basis of Presentation - Amendment to Certificate of Incorporation (Details)	Mar. 31, 2019 product
Nature of Business and Basis of Presentation
Number of late-stage candidates in Company's product candidate portfolio	4

Represents the number of late-stage candidates included in the Company's product candidate portfolio.

No definition available.

Name:	axsm_NumberOfLateStageProductCandidates
Namespace Prefix:	axsm_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant