Collaboration Agreement - Collaboration Revenue and Collaboration Receivables - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration revenue percentage compared to U.S. XTANDI net sales	50.00%	50.00%	50.00%	50.00%
Collaboration revenue related to ex-U.S. XTANDI sales	$ 15,500,000	$ 1,600,000	$ 31,200,000	$ 2,000,000
Deferred revenue, Current	4,233,000		4,233,000		16,931,000
Astellas Pharma Inc. [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Development cost-sharing payments	15,100,000	13,100,000	48,500,000	31,600,000
Commercialization cost-sharing payments	$ 7,600,000	$ 1,800,000	$ 17,800,000	$ 10,400,000
Development cost-sharing payments [Member] | Medivation Inc [Member] | Collaborative agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Share of developing and commercializing XTANDI U.S.			50.00%
Share of developing and commercializing XTANDI ex-U.S.			33.33%
Commercial cost sharing-payments [Member] | Astellas Pharma Inc. [Member] | Collaborative agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Share of developing and commercializing XTANDI U.S.			50.00%
Share of developing and commercializing XTANDI ex-U.S.			66.67%