Collaborative Arrangements and Licensing Agreements, Strategic Partnerships - Biogen (Neurology) (Details) - Biogen [Member] - Agreement Entered into in December 2012 [Member] - Neurology [Member] $ in Millions	1 Months Ended
	Feb. 29, 2016 USD ($)	Feb. 28, 2015 USD ($)	Dec. 31, 2012 USD ($) Target Drug	Dec. 31, 2015 USD ($)
Collaborative Arrangement and Licensing Agreement [Abstract]
Number of targets | Target			3
Number of programs under which drugs are to be developed and commercialized | Drug			3
Upfront fee recorded as deferred revenue			$ 30
Milestone payment earned		$ 10
Cumulative payments and/or fees received				$ 40
Next potential milestone				10
Subsequent Event [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Milestone payment earned	$ 3
License Fee and Substantive Milestones [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Maximum amount of payments receivable per program				259
Development Milestones [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Maximum amount of payments receivable per program				59
Regulatory Milestones [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Maximum amount of payments receivable per program				$ 130