Collaborative Arrangements (Details 3) (USD $)	12 Months Ended			1 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Nov. 30, 2012 Research Collaboration and License Agreement Merck Item	Dec. 31, 2013 Research Collaboration and License Agreement Merck	Dec. 31, 2012 Research Collaboration and License Agreement Merck	Oct. 31, 2012 Research Collaboration and License Agreement Merck Maximum
Information related to collaborative arrangements
Upfront payment				$ 5,000,000
Potential future contingent payments receivable							148,000,000
Initial research term				12 months
Number of units of accounting based on the relative selling price method				3
Upfront payment received allocated to license				4,400,000
Upfront payment received allocated to research services				400,000
Upfront payment received allocated to committee participation				200,000
Increase in revenue due to revised estimated performance period					206,000
Revenues	$ 3,556,000	$ 135,758,000	$ 24,512,000		$ 226,000	$ 4,400,000