Summary of Significant Accounting Policies - Narratives (Details)	Sep. 30, 2019 RevenueStream
Summary of Significant Accounting Policies [Abstract]
Number of revenue agents	3

The number of revenue agents from the collaboration agreement.

No definition available.

Name:	akca_NumberOfRevenueAgents
Namespace Prefix:	akca_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant