Collaboration Agreements - Schedule of Collaboration Revenue Attributable to Sales (Detail) (U.S. XTANDI sales [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013
Collaborative Arrangements [Line Items]
Shared U.S. development and commercialization costs	$ (57,670)
Pre-tax U.S. profit	17,708
Collaboration revenue attributable to U.S. XTANDI sales	37,689
Astellas [Member]
Collaborative Arrangements [Line Items]
Net U.S. sales (as reported by Astellas)	75,378
Medivation [Member]
Collaborative Arrangements [Line Items]
Medivation's share of pre-tax U.S. profit	8,854
Reimbursement of Medivation's share of shared U.S. costs	$ 28,835