Collaboration Agreements - Schedule of Collaboration Revenue Attributable to Sales (Detail) (U.S. XTANDI sales [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration revenue attributable to U.S. XTANDI sales	$ 196,208	$ 35,752
Astellas Pharma Inc. [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Net U.S. sales (as reported by Astellas)	392,415	71,504
Shared U.S. development and commercialization costs	(241,106)	(88,908)
Pre-tax U.S. profit (loss)	151,309	(17,404)
Medivation [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Medivation's share of pre-tax U.S. profit (loss)	75,655	(8,702)
Reimbursement of Medivation's share of shared U.S. costs	$ 120,553	$ 44,454