Discontinued Operations (Schedule Of Calculation Of Net loss On Disposal) (Detail) (USD $) In Millions, unless otherwise specified	1 Months Ended	12 Months Ended
Mar. 13, 2012	Dec. 31, 2012
Schedule of Variable Interest Entities for Loans to Commercial Borrowers [Line Items]
Carrying value of equity method investment divested		$ (394.2)
Alkermes Plc [Member]
Schedule of Variable Interest Entities for Loans to Commercial Borrowers [Line Items]
Share proceeds	380.9
Initial carrying value of available for sale investment		126.5
Carrying value of equity method investment divested		(394.2)
Net loss		(13.3)
Alkermes Plc [Member] \| Discontinued Operations [Member]
Schedule of Variable Interest Entities for Loans to Commercial Borrowers [Line Items]
Share proceeds		398.5
Initial carrying value of available for sale investment		126.5
Carrying value of equity method investment divested		(520.7)
Transaction costs		(17.6)
Net loss		$ (13.3)

Equity Method Investments Available for Sale Carrying Amount

No definition available.

Name:	eln_EquityMethodInvestmentsAvailableForSaleCarryingAmount
Namespace Prefix:	eln_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	eln_ScheduleOfVariableInterestEntitiesForLoansToCommercialBorrowersLineItems
Namespace Prefix:	eln_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

This element represents the aggregate cost of investments accounted for under the equity method of accounting.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.12)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 12

-Article 5

+ Details

Name:	us-gaap_EquityMethodInvestmentAggregateCost
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

This item represents the amount of net sales proceeds received on disposal of an equity method investment.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 323

-SubTopic 10

-Section 35

-Paragraph 35

-URI http://asc.fasb.org/extlink&oid=7658923&loc=d3e32847-111569

+ Details

Name:	us-gaap_EquityMethodInvestmentNetSalesProceeds
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

This item represents the amount of gain (loss) arising from the disposal of an equity method investment.

+ References

No definition available.

+ Details

Name:	us-gaap_EquityMethodInvestmentRealizedGainLossOnDisposal
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

This item represents the carrying amount of the entity's equity method investment which has been sold. This item is used only for purposes of disclosing the calculated gain (loss) on disposal of the subject equity method investment and not for reporting the carrying value of equity method investments as presented on the entity's balance sheet. For reporting the carrying value of equity method investments presented on the entity's balance sheet, the EquityMethodInvestments (Equity Method Investments) element would be used.

+ References

No definition available.

+ Details

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