Collaborative Arrangements and Licensing Agreements, Strategic Partnerships - Biogen (Neurology) (Details) - Neurology [Member] $ in Millions	1 Months Ended	12 Months Ended
	Dec. 31, 2012 USD ($) Target	Dec. 31, 2016 USD ($) Program
Collaborative Arrangement and Licensing Agreement [Abstract]
Number of targets | Target	3
Number of programs under which drugs are to be developed and commercialized | Program		3
Upfront payment recorded as deferred revenue	$ 30
Maximum amount of payments receivable per program for license fees and substantive milestone payments		$ 259
Maximum amount of payments receivable per program for development milestones		59
Maximum amount of payments receivable per program for regulatory milestones		130
Cumulative payments received		43
Next prospective milestone		$ 10