Collaborative Arrangements and Licensing Agreements, Biogen Idec (Strategic Neurology) (Details) (USD $)	3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended			1 Months Ended			0 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 Biogen Idec [Member] Collaborations and Licensing Agreements [Member]	Sep. 30, 2013 Biogen Idec [Member] Collaborations and Licensing Agreements [Member]	Sep. 30, 2014 Biogen Idec [Member] Collaborations and Licensing Agreements [Member]	Sep. 30, 2013 Biogen Idec [Member] Collaborations and Licensing Agreements [Member]	Sep. 30, 2014 Biogen Idec [Member] Collaborations and Licensing Agreements [Member] Strategic Neurology [Member]	Jun. 30, 2014 Biogen Idec [Member] Agreement entered into in September 2013 [Member] Strategic Neurology [Member]	Sep. 30, 2013 Biogen Idec [Member] Agreement entered into in September 2013 [Member] Strategic Neurology [Member]	Sep. 30, 2014 Biogen Idec [Member] Agreement entered into in September 2013 [Member] Strategic Neurology [Member]	Nov. 07, 2014 Biogen Idec [Member] Agreement entered into in September 2013 [Member] Strategic Neurology [Member] Subsequent Event [Member]	Sep. 30, 2014 Biogen Idec [Member] Agreement entered into in September 2013 [Member] Strategic Neurology [Member] Antisense drug for neurological disease [Member] License fee and substantive milestones [Member]	Sep. 30, 2014 Biogen Idec [Member] Agreement entered into in September 2013 [Member] Strategic Neurology [Member] Antisense drug for neurological disease [Member] Research and development milestones [Member]	Sep. 30, 2014 Biogen Idec [Member] Agreement entered into in September 2013 [Member] Strategic Neurology [Member] Antisense drug for neurological disease [Member] Regulatory milestones [Member]	Sep. 30, 2014 Biogen Idec [Member] Agreement entered into in September 2013 [Member] Strategic Neurology [Member] Other modalities [Member] Pre-specified events [Member]	Sep. 30, 2014 Biogen Idec [Member] Agreement entered into in September 2013 [Member] Strategic Neurology [Member] Other modalities [Member] Research and development milestones [Member]	Sep. 30, 2014 Biogen Idec [Member] Agreement entered into in September 2013 [Member] Strategic Neurology [Member] Other modalities [Member] Regulatory milestones [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Period of exclusive rights to use antisense technology									6 years		6 years
Upfront fee recorded as deferred revenue											$ 100,000,000
Period during which a change in control could result in requirement to refund upfront payment											6 years
Maximum amount of payments receivable per drug under strategic alliance														260,000,000
Maximum amount of payment receivable per drug															60,000,000	130,000,000	90,000,000	35,000,000	55,000,000
Milestone payment earned										10,000,000			10,000,000
Next prospective milestone												10,000,000
Revenue earned	44,063,000	23,585,000	129,300,000	105,036,000	31,700,000	5,900,000	76,400,000	17,100,000
Percent of total revenue (in hundredths)					72.00%		59.00%
Deferred revenue					$ 127,400,000		$ 127,400,000