Technology Licensing Agreements (Details) (USD $)	12 Months Ended			1 Months Ended		12 Months Ended						1 Months Ended		12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Aug. 31, 2010 License Agreement with Astellas Pharma Inc.	Mar. 31, 2007 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, 2011 License Agreement with AstraZeneca UK Limited payment	Feb. 28, 2007 License Agreement with AstraZeneca UK Limited	Dec. 31, 2011 License Agreement with AstraZeneca UK Limited	Dec. 31, 2010 License Agreement with AstraZeneca UK Limited	Dec. 31, 2009 License Agreement with AstraZeneca UK Limited	Dec. 31, 2008 License Agreement with AstraZeneca UK Limited	Dec. 31, 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				$ 20,000,000	$ 20,000,000	$ 20,000,000	$ 20,000,000
Advance payment received due to amended licensing agreement			165,000,000	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	23,571,000	24,858,000	40,150,000			23,600,000	22,000,000	20,000,000						2,900,000	20,000,000
Period over which annual payment is recognized as revenue															12 months	12 months	12 months	12 months
Number of annual payments not received due to cancellation of obligation												2
Deferred revenue						$ 128,200,000	$ 151,700,000