Collaboration and Contract Research Agreements (Details) (USD $)	12 Months Ended						1 Months Ended			12 Months Ended			1 Months Ended		12 Months Ended					1 Months Ended					3 Months Ended	12 Months Ended			1 Months Ended	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Collaboration Agreement with Sanofi [Member] Integer	Dec. 31, 2010 Collaboration Agreement with Sanofi [Member]	Dec. 31, 2009 Collaboration Agreement with Sanofi [Member]	Jan. 31, 2006 Collaboration Agreement with Sanofi [Member] ZALTRAP Agreement [Memeber]	Jan. 31, 2005 Collaboration Agreement with Sanofi [Member] ZALTRAP Agreement [Memeber]	Jan. 31, 2003 Collaboration Agreement with Sanofi [Member] ZALTRAP Agreement [Memeber]	Dec. 31, 2011 Collaboration Agreement with Sanofi [Member] ZALTRAP Agreement [Memeber] Percent	Dec. 31, 2010 Collaboration Agreement with Sanofi [Member] ZALTRAP Agreement [Memeber]	Dec. 31, 2009 Collaboration Agreement with Sanofi [Member] ZALTRAP Agreement [Memeber]	Dec. 31, 2007 Collaboration Agreement with Sanofi [Member] Antibody Collaboration [Member]	Nov. 30, 2007 Collaboration Agreement with Sanofi [Member] Antibody Collaboration [Member]	Dec. 31, 2011 Collaboration Agreement with Sanofi [Member] Antibody Collaboration [Member] Percent Integer	Dec. 31, 2010 Collaboration Agreement with Sanofi [Member] Antibody Collaboration [Member]	Dec. 31, 2009 Collaboration Agreement with Sanofi [Member] Antibody Collaboration [Member]	Nov. 30, 2009 Collaboration Agreement with Sanofi [Member] Antibody Collaboration [Member]	Dec. 31, 2011 Collaboration Agreement with Sanofi [Member] VelociGene Agreement [Member]	Jan. 31, 2011 Collaboration Agreement with Bayer HealthCare LLC [Member]	Dec. 31, 2010 Collaboration Agreement with Bayer HealthCare LLC [Member]	Jul. 31, 2009 Collaboration Agreement with Bayer HealthCare LLC [Member]	Aug. 31, 2007 Collaboration Agreement with Bayer HealthCare LLC [Member]	Oct. 31, 2006 Collaboration Agreement with Bayer HealthCare LLC [Member]	Dec. 31, 2010 Collaboration Agreement with Bayer HealthCare LLC [Member] Integer	Dec. 31, 2011 Collaboration Agreement with Bayer HealthCare LLC [Member] Percent	Dec. 31, 2010 Collaboration Agreement with Bayer HealthCare LLC [Member]	Dec. 31, 2009 Collaboration Agreement with Bayer HealthCare LLC [Member]	Sep. 30, 2006 Grant from National Institutes of Health [Member]	Dec. 31, 2011 Grant from National Institutes of Health [Member]	Dec. 31, 2010 Grant from National Institutes of Health [Member]	Dec. 31, 2009 Grant from National Institutes of Health [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Total number of newly issued unregistered shares of common stock purchased (in shares)				15,816,953
Collaboration development revenue										$ 17,500,000	$ 26,400,000	$ 36,500,000			$ 309,100,000	$ 284,900,000	$ 210,700,000									$ 43,100,000	$ 75,400,000	$ 67,300,000
Amount of non-refundable payment received for collaboration agreement							25,000,000	25,000,000	80,000,000					85,000,000										75,000,000
Number of newly issued, unregistered shares of Common Stock purchased (in shares)									2,799,552				12,000,000
Cash price of newly issued, unregistered shares of Common Stock purchased									45,000,000				312,000,000
Royalty based on percentage of annual sales in Japan (in hundredths)										35.00%
Maximum amount of milestone payments that may be received relating to marketing approvals				400,000,000
Maximum amount of milestone payments that may be received if certain sales are achieved															250,000,000
Maximum amount of milestone payments that may be received relating to marketing approvals in the U.S. or European Union				360,000,000
Maximum number of product candidates for which milestone payments may be received relating to marketing approvals in the U.S. or European Union				8
Maximum amount of milestone payments that may be received relating to marketing approvals in Japan				40,000,000
Maximum number of product candidates for which milestone payments may be received relating to marketing approvals in Japan				5
Percentage of development expenses to be reimbursed due to profitability of agreement (in hundredths)										50.00%					50.00%											50.00%
Development expenses incurred to date				763,400,000											582,300,000											370,900,000
Number of years of first commercial sale of the product (in years)										2Y
Reimbursement of development expenses in accordance with formula until first commercial sale										7,500,000
Minimum advance notice required to terminate collaboration agreement										12M					3M											six months or twelve months
Increase (decrease) in collaboration revenue recognized based on shortened (extended) performance period															(5,300,000)
Amounts receivable from collaboration agreements	74,781,000	79,603,000									3,900,000				78,500,000	75,700,000										4,500,000
Deferred revenue										22,900,000	32,600,000				83,100,000	84,000,000					47,000,000				47,000,000	42,400,000	47,000,000
Annual funding maximum of research activities through 2017 per amended agreement																		160,000,000
Adjusted maximum amount of annual funding per amended agreement																	120,000,000
Amount of research funded during the period																137,700,000
Balance between amount funded and annual funding maximum																22,300,000
Option to extend (in years)															3Y
Substantive milestone payment to be received if option to license rights is exercised															10,000,000
Number of therapeutic antibodies currently under development															7
Percentage of Shared Phase 3 Trial Costs borne by collaborating party (in hundredths)															80.00%
Percentage of Shared Phase 3 Trial Costs borne by entity (in hundredths)															20.00%
Percentage of Shared Phase 3 Trial Costs to be reimbursed due to profitability of agreement															30.00%
Excess share of profit not required to to be applied to reimburse development cost (in hundredths)															10.00%
Starting share of profits outside the United States, based on sales, for collaborating party (in hundredths)															65.00%
Starting share of profits outside the United States, based on sales, for Company (in hundredths)															35.00%
Ending share of profits outside the United States, based on sales, for collaborating party (in hundredths)															55.00%
Ending share of profits outside the United States, based on sales, for Company (in hundredths)															45.00%
Share of losses outside the United States, for collaborating party (in hundredths)															55.00%
Share of losses outside the United States, for Company (in hundredths)															45.00%
Conditions for commencement of sales milestone payments															only if and after aggregate annual sales outside the United States exceed $1.0 billion on a rolling 12-month basis
Amount of funding of agreed-upon cost incurred to expand manufacturing capacity															30,000,000
Amount of funding to expand manufacturing capacity that has been received or is receivable															28,200,000
Period of notice to opt-out of further development and/or commercialization (in months)															12M
Period of notice to opt-out of further development upon entering of joint development product (in days)															30D
Minimum payments expected to be received under the agreement																			21,500,000
Amount of milestone payment received																				10,000,000	10,000,000	20,000,000	20,000,000
Number of substantive milestone payments earned																									2
Amount of milestone payments earned																									20,000,000
Maximum amount of milestone payments that may be received related to marketing approvals in major market countries outside the U.S.																										50,000,000
Maximum amount of sales milestone payments if total sales achieve specific levels																										135,000,000
Starting specified levels of annual sales at which sales milestone payments may be received																										200,000,000
Additional research and development expenses obligated to reimburse																										47,800,000	48,900,000	37,700,000
Expenses under the collaboration payable to collaborating party										3,700,000
Minimum amount of research funding																													25,300,000
Period of funding (in years)																													5Y
Additional funding to optimize certain existing technology																													1,500,000
Contract research revenue	6,599,000	6,945,000	6,434,000																											3,600,000	4,600,000	5,500,000
Shared Pre-Launch Commercialization Expenses With Collaborator										9,300,000
Company-incurred expenses associated with Sanofi collaborations				381,200,000	282,400,000	209,400,000
Payable to Bayer HealthCare																					$ 2,300,000				$ 2,300,000		$ 2,300,000