Technology Licensing Agreements (Details) (USD $)	1 Months Ended		12 Months Ended
	Aug. 31, 2010	Mar. 31, 2007	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Deferred Revenue Arrangement [Line Items]
Technology licensing revenue			$ 31,941,000	$ 28,506,000	$ 26,471,000
License Agreement with Astellas Pharma Inc.
Deferred Revenue Arrangement [Line Items]
Non-exclusive license agreement term		6 years
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			23,600,000	23,600,000	23,600,000
Deferred Revenue			$ 81,000,000	$ 104,600,000