Significant Contracts, Grants, License and Royalty Agreements - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	1 Months Ended	12 Months Ended
	Jul. 31, 2011 Product	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Additional milestone payments related to active in-license agreements		$ 7.5
City of Hope [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
License fees		0.1	0.1	2.6
CytRx [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
License fees		0.1	0.3	0.1
CytRx [Member] | Up-front Payment [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
License fees			3.8
Collaborative Arrangement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Number of licensed products Astellas agrees to develop	1
Recognized license revenue	25.0	1.6	0.7	10.7
Milestone payment upon finalization of the trial design				10.0
Additional cash payments for achievement through commercial launch				95.0
Revenue related to contract services delivered		7.8	4.4	3.9
Revenue related to drug product delivered		$ 5.5	$ 1.2	$ 1.8