FAIR VALUE MEASUREMENTS (Details 2) (USD $) In Thousands, unless otherwise specified	6 Months Ended
Jun. 30, 2014 item
Roll forward of the fair value of the Company's investments whose fair value was determined using Level 3 inputs
Number of investments transferred from level 1 to level 2	0
Number of investments transferred from level 2 to level 1	0
Balance at the beginning of the period	$ 1,526
Total unrealized losses included in other comprehensive (loss) income	(383)
Sale of equity securities	$ (1,143)

Represents the number of investments transferred into level 2 from level 1 of the fair value hierarchy.

No definition available.

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Period Type:	duration

- Definition

Represents the number of investments transferred into level 1 from level 2 of the fair value hierarchy.

+ References

No definition available.

+ Details

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Namespace Prefix:	alks_
Data Type:	xbrli:integerItemType
Balance Type:	na
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- Details

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- Definition

Amount of gain (loss) recognized in other comprehensive income (loss) for financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1a)

-URI http://asc.fasb.org/extlink&oid=25499696&loc=d3e19207-110258

+ Details

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- Definition

Amount of sale of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)

-URI http://asc.fasb.org/extlink&oid=25499696&loc=d3e19207-110258

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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- Definition

Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=25499696&loc=d3e19207-110258

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant