Earnings Per Share (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	1 Months Ended		3 Months Ended		9 Months Ended		54 Months Ended
	Jun. 30, 2013	Feb. 28, 2013	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013
Earnings Per Share [Abstract]
Net income			$ 372,500,000	$ 424,200,000	$ 1,235,500,000	$ 1,193,100,000
Weighted average shares:
Basic (in shares)			412.3	427.2	414.7	434.1
Effect of dilutive securities:
Options, restricted stock units, warrants and other incentives			16.5	9.1	15.8	9.3
Diluted (in shares)			428.8	436.3	430.5	443.4
Net income per share attributable to Celgene:
Basic (in dollars per share)			$ 0.90	$ 0.99	$ 2.98	$ 2.75
Diluted (in dollars per share)			$ 0.87	$ 0.97	$ 2.87	$ 2.69
Anti-dilutive securities
Antidilutive securities excluded from computation of earnings per share (in shares)			4.1	11.6	5.1	11.5
Approved common share repurchase amount	$ 3,000,000,000	$ 600,000,000			$ 2,790,000,000		$ 9,500,000,000
Shares repurchased under share repurchase program					5.2
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price					$ 114.30
Common stock repurchased under the program during the period (in shares)			1.5		17.8