Collaboration Agreements - Schedule of Collaboration Revenue Attributable to Sales (Detail) (U.S. XTANDI sales [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Collaborative Arrangements [Line Items]
Collaboration revenue attributable to U.S. XTANDI sales	$ 54,244	$ 7,056	$ 133,134	$ 7,056
Astellas Pharma Inc [Member]
Collaborative Arrangements [Line Items]
Net U.S. sales (as reported by Astellas)	108,487	14,112	266,267	14,112
Shared U.S. development and commercialization costs	(58,901)	(41,928)	(178,002)	(41,928)
Pre-tax U.S. profit (loss)	49,586	(27,816)	88,265	(27,816)
Medivation [Member]
Collaborative Arrangements [Line Items]
Medivation's share of pre-tax U.S. profit (loss)	24,793	(13,908)	44,133	(13,908)
Reimbursement of Medivation's share of shared U.S. costs	$ 29,451	$ 20,964	$ 89,001	$ 20,964