Technology Licensing Agreements (Details) (USD $)	12 Months Ended			1 Months Ended		12 Months Ended							1 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Aug. 31, 2010 License Agreement with Astellas Pharma Inc.	Mar. 31, 2007 License Agreement with Astellas Pharma Inc.	Dec. 31, 2013 License Agreement with Astellas Pharma Inc.	Dec. 31, 2012 License Agreement with Astellas Pharma Inc.	Dec. 31, 2011 License Agreement with Astellas Pharma Inc.	Dec. 31, 2010 License Agreement with Astellas Pharma Inc.	Dec. 31, 2009 License Agreement with Astellas Pharma Inc.	Dec. 31, 2008 License Agreement with Astellas Pharma Inc.	Dec. 31, 2007 License Agreement with Astellas Pharma Inc.	Feb. 28, 2007 License Agreement with AstraZeneca UK Limited
Deferred Revenue Arrangement [Line Items]
Non-exclusive license agreement term					6 years								6 years
Annual, non-refundable licensing payment received									$ 20,000,000	$ 20,000,000	$ 20,000,000	$ 20,000,000
Advance payment received due to amended licensing agreement				165,000,000
Recognition period for advance payment						7 years
Future payment to be made under terms of amended licensing agreement						130,000,000
Number of days of advance written notice to terminate agreement						90 days
Technology licensing revenue	28,506,000	26,471,000	31,457,000			23,600,000	23,600,000	22,000,000
Deferred revenue						$ 104,600,000	$ 128,200,000