License and Collaboration Agreements (Details) (USD $)	3 Months Ended		6 Months Ended		24 Months Ended	3 Months Ended	1 Months Ended	3 Months Ended		6 Months Ended			3 Months Ended	1 Months Ended	3 Months Ended		6 Months Ended		1 Months Ended		3 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 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	Jun. 30, 2013 License and Collaboration Agreements Sanofi	Jun. 30, 2012 License and Collaboration Agreements Sanofi	Jun. 30, 2013 License and Collaboration Agreements Sanofi	Jun. 30, 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	Jun. 30, 2013 License and Collaboration Agreements PharmaEngine	Jun. 30, 2012 License and Collaboration Agreements PharmaEngine	Jun. 30, 2013 License and Collaboration Agreements PharmaEngine	Jun. 30, 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	2,500,000	2,500,000
Milestone payments								521,000	521,000	1,042,000	1,933,000
Development services								14,682,000	9,160,000	26,272,000	17,302,000
Manufacturing services and other								1,999,000	1,106,000	2,740,000	1,627,000
Total								18,452,000	12,037,000	32,554,000	23,362,000
Assets and liabilities related to collaboration agreement
Accounts receivable, billed								1,789,000		1,789,000		1,577,000
Accounts receivable, unbilled								12,746,000		12,746,000		7,690,000
Deferred revenue								78,060,000		78,060,000		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	42,465,000	28,758,000	79,454,000	60,409,000											200,000	300,000	500,000	5,600,000
Milestone payment																					$ 5,000,000