Collaborative and Other Relationships (Details Textual)	12 Months Ended				3 Months Ended		12 Months Ended			3 Months Ended	12 Months Ended	3 Months Ended			1 Months Ended	12 Months Ended	1 Months Ended			3 Months Ended			12 Months Ended			12 Months Ended			12 Months Ended							1 Months Ended		12 Months Ended
	Dec. 31, 2012 USD ($)	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)	Jan. 31, 2007 Biogen Idec Hemophilia	Mar. 31, 2009 Elan USD ($)	Sep. 30, 2008 Elan USD ($)	Dec. 31, 2012 Elan USD ($)	Dec. 31, 2011 Elan USD ($)	Dec. 31, 2010 Elan USD ($)	Sep. 30, 2011 Acorda USD ($)	Dec. 31, 2012 Acorda USD ($)	Dec. 31, 2011 Portola Pharmaceuticals USD ($)	Dec. 31, 2012 Portola Pharmaceuticals USD ($)	Dec. 31, 2012 AbbVie USD ($)	Jun. 30, 2011 Genentech USD ($)	Dec. 31, 2012 Swedish Orphan Biovitrum USD ($)	Dec. 31, 2012 ISIS Pharmaceuticals USD ($)	Jun. 30, 2012 ISIS Pharmaceuticals USD ($)	Jan. 31, 2012 ISIS Pharmaceuticals USD ($)	Dec. 31, 2012 ISIS Pharmaceuticals USD ($)	Jun. 30, 2012 ISIS Pharmaceuticals USD ($)	Mar. 31, 2012 ISIS Pharmaceuticals USD ($)	Dec. 31, 2012 RITUXAN USD ($)	Dec. 31, 2011 RITUXAN	Dec. 31, 2010 RITUXAN	Dec. 31, 2012 RITUXAN Maximum	Dec. 31, 2012 RITUXAN Minimum	Jun. 30, 2011 RITUXAN Genentech USD ($)	Dec. 31, 2012 New Anti-CD20	Dec. 31, 2012 Ocrelizumab Maximum	Dec. 31, 2012 Ocrelizumab Minimum	Dec. 31, 2012 GA101 USD ($)	Dec. 31, 2010 GA101 USD ($)	Dec. 31, 2012 GA101 Maximum	Dec. 31, 2012 GA101 Minimum	Feb. 29, 2012 Samsung Biosimilar Agreement USD ($)	Feb. 29, 2012 Samsung Biosimilar Agreement KRW	Dec. 31, 2012 Samsung Biosimilar Agreement USD ($)	Dec. 31, 2012 Samsung Biosimilar Agreement KRW	Dec. 31, 2012 New Anti-CD20 Third Party Anti CD-20 Roche Group - Genentech USD ($)	Dec. 31, 2011 New Anti-CD20 Third Party Anti CD-20 Roche Group - Genentech USD ($)	Dec. 31, 2010 New Anti-CD20 Third Party Anti CD-20 Roche Group - Genentech USD ($)
Collaborative arrangements and non-collaborative arrangement transactions
Significant Receivables Or Payables Related To Cost Sharing Arrangements With Unconsolidated Variable Interest Entities	$ 0	$ 0
Investments By Third Party In Joint Venture As Per Agreement.																																				250,000,000	280,500,000,000
Collaborative and Other Relationships (Textual)
Future royalties percentage to be received on sale of ocrelizumab																														24.00%	13.50%
Percentage of future development and commercialization expenses payable related to GA101																																35.00%
Profit sharing on sale of GA 101, percentage																																		39.00%	35.00%
Sharing percentage of development expenses of GA 101, Prior to Amendment																																30.00%
Compensation payment under terms of Amendment for reimbursement of increased share of previously incurred expenses																																	10,000,000
Percentage of royalties as per collaboration																										12.00%	10.00%
Royalties to be received under the collaboration agreement																							10% and 12% on sales of RITUXAN outside the U.S. and Canada, with the royalty period lasting 11 years
Period of collaboration agreement																							11 years						11 years
Royalty period for substantially all of the remaining royalty-bearing sales of RITUXAN in the rest of world																							expire through 2012
Percentage of Co promotion Operating Profits first fifty million																							30.00%
Percentage of share of co-promotion profits exceeding $50 million, prior to October 2010 amendment.																							40.00%
Co-promotion operating profit threshold for Rituxan in U S and Canada to determine share of co promotion operating profit prior to amendment																							50,000,000
GA101 CLL Sales Trigger - US GA101 gross sales threshold																																500,000,000
Limit of gross sale of GA 101 to be achieved in preceding 12 months under option one																																150,000,000
Limit of gross sale of GA 101 to be achieved in any 12 months under option one																																150,000,000
Limit of gross sale of new product to be achieved in any calendar year under sub option one and two of option two																							150,000,000
Threshold of gross sales of GA 101 to be achieved in any 12 consecutive months under option two																							150,000,000
Threshold of gross sales of new product to be achieved in any calendar year under sub option three of option two																							350,000,000
Estimates of compensatory damages and interest															125,000,000
Estimated range of possible loss, related to reduction of share of revenues																												50,000,000
Percentage of share of Co promotion profits exceeding $50 million																							40.00%	40.00%	40.00%
Research and development	1,334,919,000	1,219,602,000	1,248,604,000									36,800,000								30,000,000	12,000,000	29,000,000																		35,400,000	26,900,000	50,600,000
Milestone payments received under collaboration agreement					50,000,000	75,000,000
Milestone payment to be amortized							92,400,000
Deferred revenue for the inventory pending shipment of TYSABRI							24,900,000	23,800,000
Reimbursements of research and developments expense from Elan							43,700,000	47,500,000	49,800,000
Reimbursements of selling general and administrative expenses from Elan							99,900,000	77,300,000	68,500,000
Amount reflected in collaboration profit sharing line for collaboration							317,900,000	317,800,000	258,100,000
Total milestone payments										25,000,000
Expected additional milestone payments for successful achievement of regulatory and commercial sales milestones											375,000,000		406,800,000
Expected additional milestone payments when certain sales threshold is met											15,000,000
Foreign sales required to trigger milestone											100,000,000
Stock acquired in acquisition				100.00%
Consideration per product																10,000,000
Percentage of reimbursement expenses																50.00%
Percentage of development reimbursement expenses																100.00%
Reimbursement cost achieving period																6 years
Time period for paying remaining balance due																90 days
Term for revocation option right																18 months
Estimated additional payments upon achievement of development and commercial milestones.														60,000,000
Amount paid to purchase Portola equity												8,200,000
Payments to Acquire Equity Method Investments																																						32,100,000	36,000,000,000
Remaining obligation of financing arrangements																																						12,500,000	13,500,000,000
Joint Venture Owner Ship Percentage By Third Party.																																				85.00%	85.00%
Equity Method Investments																																				45,000,000	49,500,000,000	27,800,000	29,700,000,000
Percentage of equity interest to the portion of total capital stock																																				15.00%	15.00%
Equity Method Investment Ownership Percentage Maximum																																				49.90%	49.90%
Income (Loss) from Equity Method Investments	(4,518,000)	0	0																																			(4,500,000)
Revenues Related To Technical Development And Technology Transfer Services																																						13,300,000
Deferred revenue	148,000,000	69,600,000																																				11,200,000
Additional Milestone Payment																	10,000,000	59,000,000	45,000,000	10,000,000	59,000,000
Phase Two By Three Milestone Payment																			18,000,000
License Fee																	70,000,000	70,000,000	75,000,000
Expected License Fee And Regulatory Milestone Payments																	$ 148,000,000	$ 130,000,000	$ 150,000,000	$ 148,000,000	$ 130,000,000