Earnings Per Share (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	1 Months Ended	3 Months Ended
	Feb. 28, 2013	Mar. 31, 2013	Mar. 31, 2012
Earnings Per Share
Net income		$ 384.9	$ 401.5
Weighted average shares:
Basic (in shares)		417.9	438.3
Effect of dilutive securities:
Options, restricted stock units, warrants and other incentives (in shares)		14.3	10.3
Diluted (in shares)		432.2	448.6
Net income per share attributable to Celgene:
Basic (in dollars per share)		$ 0.92	$ 0.92
Diluted (in dollars per share)		$ 0.89	$ 0.90
Anti-dilutive securities
Antidilutive securities excluded from computation of earnings per share (in shares)		2.0	5.2
Approved common share repurchase amount	600.0	6,500.0
Aggregate common stock repurchased under the program (in shares)		81.6
Shares repurchased under share repurchase program		3.0
Shares purchased under share repurchase program		300.0
Amount included in Additional paid-in capital		300.0
Common stock repurchased under the program during the period (in shares)		7.2
Amount paid under the ASR		600.0
Remaining open-ended repurchase authorization		$ 834.2