Nature of Business and Basis of Presentation Nature of Business and Basis of Presentation (Details)	9 Months Ended
Sep. 30, 2013 Systemic_Therapy
Nature of Business and Basis of Presentation [Abstract]
Number of Prior Systemic Therapies	2
Period for Demonstration of Disease Progression from Completion of Last Therapy	60 days
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