Collaborative Arrangements and Licensing Agreements, Traditional Pharmaceutical Alliances and Licensing - Biogen Idec (ISIS-DMPK) (Details) (Biogen Idec [Member], Agreement Entered into in June 2012 [Member], ISIS-DMPK [Member], USD $) In Millions, unless otherwise specified	1 Months Ended
	Jun. 30, 2012	Mar. 31, 2015
Collaborative Arrangement and Licensing Agreement [Abstract]
Upfront fee recorded as deferred revenue	$ 12
Cumulative payments received		36.0
Next prospective milestone		35.0
License Fee and Substantive Milestones [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Maximum amount of payments receivable		259.0
Development Milestones [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Maximum amount of payments receivable		59.0
Regulatory Milestones [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Maximum amount of payments receivable		$ 130.0