Nature of Business and Basis of Presentation (Narrative) (Details)	9 Months Ended
Sep. 30, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Maximum equity ownership percentage, investments	50.00%

Represents the maximum ownership percentage held by the entity for the investment to be accounted for under the equity or cost method.

No definition available.

Name:	celg_MaximumEquityOwnershipPercentageInvestments
Namespace Prefix:	celg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration