THE COMPANY (Details)	12 Months Ended
Mar. 31, 2013 product
THE COMPANY
Minimum number of commercial drug products in Company's diversified portfolio	20

Represents the minimum number of commercial drug products in portfolio.

No definition available.

Name:	alks_MinimumNumberOfCommercialDrugProductsInPortfolio
Namespace Prefix:	alks_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration