Nature of Business and Basis of Presentation (Details)	6 Months Ended
Jun. 30, 2012
Nature of Business and Basis of Presentation
Maximum equity interest in investment to be accounted for by either the equity or cost method (as a percent)	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