Collaboration Agreements (Sanofi) (Details) (USD $)	3 Months Ended						12 Months Ended			1 Months Ended		3 Months Ended	11 Months Ended	1 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jul. 31, 2014	Nov. 30, 2007	Jun. 30, 2013	Nov. 30, 2009	Jan. 31, 2006	Jan. 31, 2005	Sep. 30, 2003
Collaboration Agreements [Line Items]
Revenue Recognition, Milestone Method, Revenue Recognized	$ 30,000,000	$ 30,000,000	$ 15,000,000	$ 30,000,000	$ 25,000,000	$ 45,000,000
Research and Development Expense							1,271,353,000	859,947,000	625,554,000
Revenue from Related Parties							541,299,000	430,111,000	423,814,000
Number of therapeutic antibodies currently under development							5
Period for Achieving Sales Target for Milestone Payment, Rolling Basis							12 months
Collaboration Agreement with Sanofi
Collaboration Agreements [Line Items]
Common Stock, shares issued (in shares)	22,859,144						22,859,144
Antibody Collaboration
Collaboration Agreements [Line Items]
Contingent reimbursement obligation	1,304,000,000						1,304,000,000
Recognition of Deferred Revenue							10,243,000	10,243,000	10,233,000
Net profit (loss) from commercialization of products under collaboration agreement							(41,378,000)	0	0
Research and Development Arrangement, Contract to Perform for Others, Compensation Earned							547,761,000	453,489,000	365,245,000
Contracts Revenue							19,480,000	1,868,000	0
Research and Development Asset Acquired Other than Through Business Combination, Written-off							0	(20,000,000)	0
Due from Related Parties, Current	110,600,000				106,100,000		110,600,000	106,100,000
Research and Development Expense							109,700,000	17,600,000
Deferred Revenue	64,400,000				71,200,000		64,400,000	71,200,000
Revenue from Related Parties							536,106,000	445,600,000	375,478,000
Proceeds from Collaborators											85,000,000
Percentage of repayment of development balance out of profits							50.00%
Minimum advance notice required to terminate collaboration agreement							3 months
Annual funding maximum of research activities per amended agreement													160,000,000
Additional years to extend the agreement													3 years
Substantive milestone payment to the Company							10,000,000
Percentage of Trial Costs borne by collaborating party							80.00%
Percentage of Trial Costs borne by entity							20.00%
Percentage of 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							10.00%
Starting share of profits outside the United States, based on sales, for collaborating party							65.00%
Starting share of profits outside the United States, based on sales, for Company							35.00%
Ending share of profits outside the United States, based on sales, for collaborating party							55.00%
Ending share of profits outside the United States, based on sales, for Company							45.00%
Share of losses outside the United States, for collaborating party							55.00%
Share of losses outside the United States, for Company							45.00%
Maximum amount of sales milestone payments if total sales achieve specific levels							250,000,000
Starting specified levels of annual sales at which sales milestone payments may be received							1,000,000,000
Period for Achieving Sales Target for Milestone Payment, Rolling Basis							12 months
Amount of funding of agreed-upon cost incurred to expand manufacturing capacity							30,000,000
Maximum amount of reimbursement related to capital expenditures							17,500,000
Period of Notice to Opt Out of Further Development and or Commercialization							12 months
Period of Notice to Opt Out of Further Development Upon Entering of Joint Development Product							30 days
Number of families of novel antibodies								2				2
Payments for Purchase of Other Assets										67,500,000
Sanofi
Collaboration Agreements [Line Items]
Research and Development Asset Acquired Other than Through Business Combination, Written-off		(33,800,000)
VelociGene Agreement
Collaboration Agreements [Line Items]
Minimum payment received under the agreement	21,500,000						21,500,000
PDGF
Collaboration Agreements [Line Items]
Research and Development Asset Acquired Other than Through Business Combination, Written-off												(10,000,000)
Number of Payments the Company made							2
Other Research and Development Expense							5,000,000
Potential future milestone payments							30,000,000
Ang2
Collaboration Agreements [Line Items]
Research and Development Asset Acquired Other than Through Business Combination, Written-off												(10,000,000)
ZALTRAP Agreement
Collaboration Agreements [Line Items]
Contingent reimbursement obligation	461,000,000						461,000,000
Net profit (loss) from commercialization of products under collaboration agreement							(4,715,000)	(30,810,000)	(25,634,000)
Revenue Recognition, Milestone Method, Revenue Recognized							0	0	50,000,000
Research and Development Arrangement, Contract to Perform for Others, Compensation Earned							4,806,000	5,639,000	10,702,000
Contracts Revenue							5,102,000	9,682,000	13,268,000
Due from Related Parties, Current	10,500,000						10,500,000
Due to Related Parties, Current					1,400,000			1,400,000
Deferred Revenue	23,900,000				18,200,000		23,900,000	18,200,000
Revenue from Related Parties							5,193,000	(15,489,000)	48,336,000
Proceeds from Collaborators														25,000,000	25,000,000	80,000,000
Number of shares of Common Stock purchased																2,799,552
Cash price of newly issued, unregistered shares of Common Stock purchased																45,000,000
Revenue based on percentage of annual sales in Japan							35.00%
Amount of milestone payments that may be received relating to marketing approval							350,000,000
Percentage of repayment of development balance out of profits							50.00%
Amount of non refundable payment received for collaboration agreement															$ 25,000,000
Minimum advance notice required to terminate collaboration agreement							12 months
Percentage of development expenses to be reimbursed due to termination of collaboration agreement							50.00%