Collaboration and License Agreements (Details) (USD $)	3 Months Ended		6 Months Ended		1 Months Ended			3 Months Ended		6 Months Ended		12 Months Ended		3 Months Ended		6 Months Ended			1 Months Ended	3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		1 Months Ended	3 Months Ended	6 Months Ended	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Oct. 31, 2011 2003 Sandoz Collaboration Item	Jul. 31, 2011 2003 Sandoz Collaboration Item	Jul. 31, 2010 2003 Sandoz Collaboration Item	Jun. 30, 2013 2003 Sandoz Collaboration	Jun. 30, 2012 2003 Sandoz Collaboration	Jun. 30, 2013 2003 Sandoz Collaboration Item	Jun. 30, 2012 2003 Sandoz Collaboration	Dec. 31, 2011 2003 Sandoz Collaboration	Jun. 30, 2013 2003 Sandoz Collaboration Maximum	Jun. 30, 2013 Second Sandoz Collaboration Agreement	Jun. 30, 2012 Second Sandoz Collaboration Agreement	Jun. 30, 2013 Second Sandoz Collaboration Agreement Item	Jun. 30, 2012 Second Sandoz Collaboration Agreement	Jun. 30, 2013 Second Sandoz Collaboration Agreement Maximum	Jul. 31, 2006 Second Sandoz Collaboration Agreement Novartis Pharma AG	Jun. 30, 2013 Second Sandoz Collaboration Agreement Novartis Pharma AG	Jun. 30, 2012 Second Sandoz Collaboration Agreement Novartis Pharma AG	Jun. 30, 2013 Second Sandoz Collaboration Agreement Novartis Pharma AG	Jun. 30, 2012 Second Sandoz Collaboration Agreement Novartis Pharma AG	Jun. 30, 2013 Massachusetts Institute of Technology	Jun. 30, 2012 Massachusetts Institute of Technology	Jun. 30, 2013 Massachusetts Institute of Technology Item	Jun. 30, 2012 Massachusetts Institute of Technology	Jul. 31, 2012 Baxter Agreement Item	Jun. 30, 2013 Baxter Agreement	Jun. 30, 2013 Baxter Agreement Item	Jun. 30, 2013 Baxter Agreement Accounting Standards Update No. 2009-13	Jun. 30, 2012 Baxter Agreement Accounting Standards Update No. 2009-13	Jun. 30, 2013 Baxter Agreement Accounting Standards Update No. 2009-13 Item	Jun. 30, 2012 Baxter Agreement Accounting Standards Update No. 2009-13	Jun. 30, 2013 Baxter Agreement Maximum
Collaborations and License Agreements
Number of significant deliverables identified in arrangement										2						2
Number of third-party competitors					0	0	0
Percentage of contractual profits earned under collaborative arrangement										45.00%												50.00%
Profit-share product revenue earned from the collaborative agreement, net of development and legal expenses								$ 1,600,000	$ 19,400,000	$ 7,000,000	$ 41,400,000
Percentage of royalty for net sales up to pre-defined sales threshold										10.00%
Percentage of royalty for net sales above pre-defined sales threshold										12.00%
Milestone payments possible per agreement													55,000,000					163,000,000
Period since date of product approval during which no competitor marketed similar product						1 year
Reduction in product revenue due to netting of shared development and other expenses								3,800,000	3,900,000
Research and development revenue recognized from FTE services and external development costs								800,000	1,200,000	1,800,000	2,100,000			300,000	200,000	500,000	400,000
Manufacturing raw material purchases								0		0
Sales-based and commercial milestone payments possible per agreement																		153,000,000
Number of shares sold																			4,708,679
Per share price of shares sold																			$ 15.93
Closing price of the company's common stock on the NASDAQ Global Market (in dollars per share)																			$ 13.05
Aggregate purchase price of shares sold																			75,000,000
Premium paid																			13,600,000
Research and development revenue related to paid premium recognized																				300,000	500,000	600,000	1,100,000
Regulatory milestone payments possible per agreement																		10,000,000
Number of follow-on biologic products for development and commercialization																												1		2
Period of right to select additional follow-on biologic products																														3 years
Number of additional follow-on biologic products to be included in the collaboration																														3
Percentage share of Company's option to participate, at its discretion, in a cost and profit share arrangement for the four additional products																																			30.00%
Total arrangement consideration																																	61,000,000
Portion of arrangement consideration allocated to the first initial product license																																	10,300,000
Portion of arrangement consideration allocated to each of the four additional product licenses																																	10,300,000
Portion of arrangement consideration allocated to the second initial product license																																	9,400,000
Portion of arrangement consideration allocated to the joint steering committee unit of accounting																																	114,000
Upfront payment paid by Baxter to the company																														33,000,000
Option payments agreed to be paid by Baxter with respect to additional product candidates																														28,000,000
Option payments agreed to be paid for each of the extensions of the period																														5,000,000
Technical and development milestone payment agreed to be paid by Baxter																														80,000,000
Number of product candidates																														6
Aggregate regulatory milestones to be paid by Baxter																														300,000,000
Number of follow-on biologic products for development and product licenses																												1					2
Number of additional follow-on biologic products for development and product licenses																																	3
Number of follow-on biologic products for research and development services																																	2
Number of additional follow-on biologic products for research and development services																														4
Number of combined units of accounting for performance period																																	6
Number of initial product estimate for performance period																														0			2
Number of vendors selling similar, competing products on a stand-alone basis																														0
Remaining payment obligation																													0	0
Estimate performance period for the first initial product																																	5 years
Estimate performance period for the second initial product																																	7 years
Estimate performance period for the joint steering committee																																	9 years
Total potential license fees and milestones receivable upon the achievement of pre-defined minimum development																														26,000,000
Potential milestone payments, in aggregate																														380,000,000
First anticipated technical and development milestone payment																														7,000,000
Period of right of first negotiation with respect to collaborating in development of a competing product																														3 years
Number of license agreements																														6
Number of accounting units for revenue recognition																														6
Number of other time-based milestones																														0
License, maintenance and royalties recorded
License and maintenance fees																								21,000	39,000	41,000	79,000
Royalties																								12,000	366,000	99,000	786,000
Total																								33,000	405,000	140,000	865,000
Annual license maintenance fee																										100,000
Number of patents issued in the United States																										30
Term of patents from the filing date of application																										20 years
Period of nonpayment considered for immediately terminating the agreement																										60 days
Period of material breach considered for immediately terminating the agreement																										90 days
Revenue earned and recognized upon achievement of a commercial milestone												10,000,000
Revenue earned and recognized upon the achievement of a regulatory milestone							5,000,000
Revenue earned and recognized upon amortization of the upfront payment																															700,000	800,000	1,400,000	1,400,000
Revenue recognized upon activities related to biosimilars development																													600,000	600,000
Shared development costs	21,994,000	20,011,000	44,326,000	38,572,000										0		0
Reduction in research and development revenue due to netting of shared development costs															$ 300,000		$ 300,000