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License and Collaboration Agreements (Details) (USD $)	3 Months Ended		24 Months Ended	3 Months Ended	1 Months Ended	3 Months Ended			3 Months Ended	1 Months Ended	3 Months Ended		1 Months Ended		3 Months Ended
License and Collaboration Agreements (Details) (USD $)	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2011 Sanofi Phase 2 clinical trials in breast cancer and non-small cell lung cancer	Mar. 31, 2012 Sanofi Phase 2 clinical trial in ovarian cancer	Nov. 30, 2009 License and Collaboration Agreements Sanofi	Mar. 31, 2013 License and Collaboration Agreements Sanofi	Mar. 31, 2012 License and Collaboration Agreements Sanofi	Dec. 31, 2012 License and Collaboration Agreements Sanofi	Mar. 31, 2013 License and Collaboration Agreements GTC	May 31, 2011 License and Collaboration Agreements PharmaEngine	Mar. 31, 2013 License and Collaboration Agreements PharmaEngine	Mar. 31, 2012 License and Collaboration Agreements PharmaEngine	May 31, 2011 License and Collaboration Agreements PharmaEngine Development and regulatory milestone	May 31, 2011 License and Collaboration Agreements PharmaEngine Sales milestone	Mar. 31, 2012 License and Collaboration Agreements PharmaEngine Phase 3 clinical trial in pancreatic cancer
License and collaboration agreements
Upfront license fee received					$ 60,000,000
Milestone payments received			20,000,000	5,000,000
Expected development period from the effective date of agreement					12 years
Deferred revenue recognized due to a change in estimate of expected development term									600,000
Recognized revenue under collaboration agreements
Upfront payment						1,250,000	1,250,000
Milestone payments						521,000	1,412,000
Development services						11,590,000	8,142,000
Manufacturing services and other						741,000	521,000
Total						14,102,000	11,325,000
Assets and liabilities related to collaboration agreement
Accounts receivable, billed						5,217,000		1,577,000
Accounts receivable, unbilled						4,579,000		7,690,000
Deferred revenue						77,399,000		79,913,000
Collaborative arrangement additional information
Upfront license fees paid										10,000,000
Maximum milestone payment obligation													80,000,000	130,000,000
Research and development expenses	36,989,000	31,651,000									300,000	5,300,000
Milestone payment															$ 5,000,000