Name:	alks_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentOtherThanOptionsCountAgainstNumberOfSharesAvailableForGrantRatio
Namespace Prefix:	alks_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

Represents the number of equity-based compensation plans under which awards are currently made.

No definition available.

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

Represents the number of equity-based compensation plans under which no further awards will be made.

No definition available.

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

Amount of cost capitalized for award under share-based payment arrangement.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (h)(1)(ii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Name:	us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Number of additional shares authorized for issuance under share-based payment arrangement.

No definition available.

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2