Collaboration Agreements (Period End Balances) (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Intangible Asset Balance	$ 10,763.5	$ 10,858.1
Acceleron
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Intangible Asset Balance	0.0	0.0
Equity Investment Balance	$ 142.8	$ 224.9
Percentage of Outstanding Equity	15.00%	14.00%
bluebird
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Intangible Asset Balance	$ 18.1	$ 20.2
Juno
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Intangible Asset Balance	0.0	0.0
Equity Investment Balance	$ 391.4	$ 401.8
Percentage of Outstanding Equity	10.00%	9.00%
Other Collaboration Arrangements
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Intangible Asset Balance	$ 48.5	$ 52.4
Equity Investment Balance	$ 487.4	$ 702.4

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.

+ Details

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

- Definition

The percentage of ownership of common stock or equity participation in the investee 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 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571

+ Details

Name:	us-gaap_EquityMethodInvestmentOwnershipPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=35755396&loc=d3e33749-111570

Reference 2: 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

+ Details

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

- Definition

Sum of the carrying amounts of all intangible assets, excluding goodwill, as of the balance sheet date, net of accumulated amortization and impairment charges.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6388964&loc=d3e16212-109274

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph ((a)(1),(b))
-URI http://asc.fasb.org/extlink&oid=26713463&loc=d3e16323-109275

+ Details

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

- Details

Name:	celg_CollaborationAgreementsPartiesAxis=celg_AcceleronPharmaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	celg_CollaborationAgreementsPartiesAxis=celg_BluebirdBioIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	celg_CollaborationAgreementsPartiesAxis=celg_JunoTherapeuticsIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	celg_CollaborationAgreementsPartiesAxis=celg_OtherCollaborationAgreementsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: