Collaboration Agreements (Sanofi) (Details) $ in Thousands	1 Months Ended					3 Months Ended	12 Months Ended
	Jul. 30, 2016	Jul. 31, 2015 USD ($)	Jul. 31, 2014 USD ($)	Nov. 30, 2009 USD ($)	Nov. 30, 2007 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($) shares	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013
Collaboration Agreements [Line Items]
Accounts receivable - trade, net								$ 1,343,368	$ 1,152,489
Deferred revenue from Sanofi, current portion								115,267	101,573
Research and Development Expense								2,052,295	1,620,577	$ 1,271,353
Revenue from Related Parties								658,665	758,873	$ 541,299
Period for Achieving Sales Target for Milestone Payment, Rolling Basis										12 months
Other Revenue, Net								119,102	74,889	$ 31,941
Payments to Acquire Marketable Securities								809,419	557,105	564,188
Period over which we have obligation	5 years
PDGFR-beta outside the US
Collaboration Agreements [Line Items]
Research and Development Arrangement, Contract to Perform for Others, Compensation Earned								10,291	10,075	2,848
Contracts Revenue								$ 9,576	10,393	10,632
Percentage of development cost for the territory outside the United States to be paid for under the collaboration								50.00%
Deferred Revenue, Additions										2,500
Percentage of global development cost to be paid by the collaboration partner under the collaboration								25.00%
Proceeds from Collaborators										25,500
Substantive milestone payment to the Company									5,000
Collaboration Agreement with Sanofi
Collaboration Agreements [Line Items]
Common Stock, shares issued (in shares) | shares								23,418,396
IO Agreement [Member]
Collaboration Agreements [Line Items]
Deferred Revenue, Additions								$ 640,000
Antibody Collaboration
Collaboration Agreements [Line Items]
Accounts receivable - trade, net								47,268	126,687
Deferred revenue from Sanofi, current portion								98,741	84,237
Contingent reimbursement obligation								2,245,000
Recognition of Deferred Revenue								12,177	10,243	10,243
Net profit (loss) from commercialization of products under collaboration agreement								(459,058)	(240,042)	(41,378)
Research and Development Arrangement, Contract to Perform for Others, Compensation Earned								564,900	735,439	547,761
Contracts Revenue								322,149	157,350	19,480
License agreement term		3 years
Research and Development Expense								108,600	92,600	109,700
Revenue from Related Parties								$ 440,168	662,990	536,106
Proceeds from Collaborators					$ 85,000
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				$ 130,000	145,000
Reduction of Funding for Research Activities Per Agreement		$ 75,000
Substantive milestone payment to the Company									10,000
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
Starting specified levels of annual sales at which sales milestone payments may be received								$ 1,000,000
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
Maximum amount of reimbursement related to capital expenditures										17,500
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
Payments for Purchase of Other Assets			$ 67,500
Immuno-oncology Agreement [Member]
Collaboration Agreements [Line Items]
Accounts receivable - trade, net								$ 40,647	21,394
Deferred revenue from Sanofi, current portion								520,000	600,000
Contingent reimbursement obligation								3,000
Recognition of Deferred Revenue								80,000	40,000	0
Research and Development Arrangement, Contract to Perform for Others, Compensation Earned								138,497	39,961	0
Revenue from Related Parties								218,497	79,961	$ 0
Sanofi
Collaboration Agreements [Line Items]
Research and Development Asset Acquired Other than Through Business Combination, Written-off			$ (33,800)
VelociGene Agreement
Collaboration Agreements [Line Items]
Minimum payment received under the agreement								21,500
PDGF
Collaboration Agreements [Line Items]
Number of Payments the Company made										2
Other Research and Development Expense									10,000	$ 5,000
ZALTRAP Agreement
Collaboration Agreements [Line Items]
Net profit (loss) from commercialization of products under collaboration agreement								0	0	(4,715)
Research and Development Arrangement, Contract to Perform for Others, Compensation Earned								0	686	4,806
Contracts Revenue								0	15,236	5,102
Deferred Revenue, Revenue Recognized						$ 14,900
Revenue from Related Parties								0	15,922	$ 5,193
Other Revenue, Net								26,200	$ 38,800
IO Discovery Agreement [Member]
Collaboration Agreements [Line Items]
License agreement term		5 years
Deferred Revenue, Additions		$ 265,000
Potential future R&D expenses		1,090,000
Funding Maximum of Research Activities Per Agreement		$ 825,000
Annual Funding Limit - 2016								$ 150,000
Additional years to extend the agreement		3 years
Excess Share of profit not required to to be applied to reimburse development cost		10.00%
IO License and Collaboration Agreement [Member]
Collaboration Agreements [Line Items]
Deferred Revenue, Additions		$ 375,000
Excess Share of profit not required to to be applied to reimburse development cost		10.00%
Period of Notice to Opt Out of Further Development and or Commercialization		12 months
New Funding [Member] | IO Discovery Agreement [Member]
Collaboration Agreements [Line Items]
Funding Maximum of Research Activities Per Agreement		$ 750,000
Previous Funding under Antibody Discovery Agreement [Member] | IO Discovery Agreement [Member]
Collaboration Agreements [Line Items]
Funding Maximum of Research Activities Per Agreement		75,000
PD-1 [Member] | IO License and Collaboration Agreement [Member]
Collaboration Agreements [Line Items]
Levels of twelve month sales at which sales milestone payments would be received		2,000,000
Maximum amount of shared development costs		650,000
Maximum amount of sales milestone payments if total sales achieve specific levels		$ 375,000
Period for Achieving Sales Target for Milestone Payment, Rolling Basis		12 months
Minimum | ZALTRAP Agreement
Collaboration Agreements [Line Items]
Percentage of aggregate net sales to be paid by the related party in such calendar year								15.00%
Maximum | ZALTRAP Agreement
Collaboration Agreements [Line Items]
Percentage of aggregate net sales to be paid by the related party in such calendar year								30.00%
Scenario, Forecast [Member] | Antibody Collaboration
Collaboration Agreements [Line Items]
Annual funding maximum of research activities per amended agreement							$ 130,000
Subsequent Event [Member] | Antibody Collaboration
Collaboration Agreements [Line Items]
License agreement term							3 years